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Motor Control Pulse Width Modulator (MCPWM)

The MCPWM peripheral is a versatile PWM generator, which contains various submodules to make it a key element in power electronic applications like motor control, digital power and so on. Typically, the MCPWM peripheral can be used in the following scenarios:

  • Digital motor control, e.g. brushed/brushless DC motor, RC servo motor
  • Switch mode based digital power conversion
  • Power DAC, where the duty cycle is equivalent to a DAC analog value
  • Calculate external pulse width, and convert it into other analog value like speed, distance
  • Generate Space Vector PWM (SVPWM) signals for Field Oriented Control (FOC)

The main submodules are listed in the following diagram:

/../_static/diagrams/mcpwm/mcpwm_overview.diag

  • MCPWM Timer: The time base of the final PWM signal. It also determines the event timing of other submodules.
  • MCPWM Operator: The key module that is responsible for generating the PWM waveforms. It consists of other submodules, like comparator, PWM generator, dead time, and carrier modulator.
  • MCPWM Comparator: The compare module takes the time-base count value as input, and continuously compares it to the threshold value configured. When the timer is equal to any of the threshold values, a compare event will be generated and the MCPWM generator can update its level accordingly.
  • MCPWM Generator: One MCPWM generator can generate a pair of PWM waves, complementarily or independently, based on various events triggered by other submodules like MCPWM Timer and MCPWM Comparator.
  • MCPWM Fault: The fault module is used to detect the fault condition from outside, mainly via the GPIO matrix. Once the fault signal is active, MCPWM Operator will force all the generators into a predefined state to protect the system from damage.
  • MCPWM Sync: The sync module is used to synchronize the MCPWM timers, so that the final PWM signals generated by different MCPWM generators can have a fixed phase difference. The sync signal can be routed from the GPIO matrix or from an MCPWM Timer event.
  • Dead Time: This submodule is used to insert extra delay to the existing PWM edges generated in the previous steps.
  • Carrier Modulation: The carrier submodule can modulate a high-frequency carrier signal into PWM waveforms by the generator and dead time submodules. This capability is mandatory for controlling the power-switching elements.
  • Brake: MCPWM operator can set how to brake the generators when a particular fault is detected. You can shut down the PWM output immediately or regulate the PWM output cycle by cycle, depending on how critical the fault is.
  • MCPWM Capture: This is a standalone submodule that can work even without the above MCPWM operators. The capture consists one dedicated timer and several independent channels, with each channel connected to the GPIO. A pulse on the GPIO triggers the capture timer to store the time-base count value and then notify you by an interrupt. Using this feature, you can measure a pulse width precisely. What is more, the capture timer can also be synchronized by the MCPWM Sync submodule.

Functional Overview

Description of the MCPWM functionality is divided into the following sections:

  • Resource Allocation and Initialization - covers how to allocate various MCPWM objects, like timers, operators, comparators, generators and so on. These objects are the basis of the following IO setting and control functions.
  • Timer Operations and Events - describes control functions and event callbacks that supported by the MCPWM timer.
  • Comparator Operations and Events - describes control functions and event callbacks that supported by the MCPWM comparator.
  • Generator Actions on Events - describes how to set actions for MCPWM generators on particular events that generated by the MCPWM timer and comparators.
  • Classical PWM Waveforms and Generator Configurations - demonstrates some classical PWM waveforms that can be achieved by configuring generator actions.
  • Dead Time - describes how to set dead time for MCPWM generators.
  • Classical PWM Waveforms and Dead Time Configurations - demonstrates some classical PWM waveforms that can be achieved by configuring dead time.
  • Carrier Modulation - describes how to set modulate a high frequency onto the final PWM waveforms.
  • Faults and Brake Actions - describes how to set brake actions for MCPWM operators on particular fault event.
  • Generator Force Actions - describes how to control the generator output level asynchronously in a forceful way.
  • Synchronization - describes how to synchronize the MCPWM timers and get a fixed phase difference between the generated PWM signals.
  • Capture - describes how to use the MCPWM capture module to measure the pulse width of a signal.
  • Power Management - describes how different source clock will affect power consumption.
  • IRAM Safe - describes tips on how to make the RMT interrupt work better along with a disabled cache.
  • Thread Safety - lists which APIs are guaranteed to be thread safe by the driver.
  • Kconfig Options - lists the supported Kconfig options that can bring different effects to the driver.

Resource Allocation and Initialization

As displayed in the diagram above, the MCPWM peripheral consists of several submodules. Each submodule has its own resource allocation, which is described in the following sections.

MCPWM Timers

You can allocate a MCPWM timer object by calling :cppmcpwm_new_timer function, with a configuration structure :cppmcpwm_timer_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_timer_config_t::group_id specifies the MCPWM group ID. The ID should belong to [0, :cSOC_MCPWM_GROUPS - 1] range. Please note, timers located in different groups are totally independent.
  • :cppmcpwm_timer_config_t::intr_priority sets the priority of the interrupt. If it is set to 0, the driver will allocate an interrupt with a default priority. Otherwise, the driver will use the given priority.
  • :cppmcpwm_timer_config_t::clk_src sets the clock source of the timer.
  • :cppmcpwm_timer_config_t::resolution_hz set the expected resolution of the timer, the driver internally will set a proper divider based on the clock source and the resolution.
  • :cppmcpwm_timer_config_t::count_mode sets the count mode of the timer.
  • :cppmcpwm_timer_config_t::period_ticks sets the period of the timer, in ticks (the tick resolution is set in the :cppmcpwm_timer_config_t::resolution_hz).
  • :cppmcpwm_timer_config_t::update_period_on_empty sets whether to update the period value when the timer counts to zero.
  • :cppmcpwm_timer_config_t::update_period_on_sync sets whether to update the period value when the timer takes a sync signal.

The :cppmcpwm_new_timer will return a pointer to the allocated timer object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free timers in the MCPWM group, this function will return :cESP_ERR_NOT_FOUND error.1

On the contrary, calling :cppmcpwm_del_timer function will free the allocated timer object.

MCPWM Operators

You can allocate a MCPWM operator object by calling :cppmcpwm_new_operator function, with a configuration structure :cppmcpwm_operator_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_operator_config_t::group_id specifies the MCPWM group ID. The ID should belong to [0, :cSOC_MCPWM_GROUPS - 1] range. Please note, operators located in different groups are totally independent.
  • :cppmcpwm_operator_config_t::intr_priority sets the priority of the interrupt. If it is set to 0, the driver will allocate an interrupt with a default priority. Otherwise, the driver will use the given priority.
  • :cppmcpwm_operator_config_t::update_gen_action_on_tez sets whether to update the generator action when the timer counts to zero. Here and below, the timer refers to the one that is connected to the operator by :cppmcpwm_operator_connect_timer.
  • :cppmcpwm_operator_config_t::update_gen_action_on_tep sets whether to update the generator action when the timer counts to peak.
  • :cppmcpwm_operator_config_t::update_gen_action_on_sync sets whether to update the generator action when the timer takes a sync signal.
  • :cppmcpwm_operator_config_t::update_dead_time_on_tez sets whether to update the dead time when the timer counts to zero.
  • :cppmcpwm_operator_config_t::update_dead_time_on_tep sets whether to update the dead time when the timer counts to peak.
  • :cppmcpwm_operator_config_t::update_dead_time_on_sync sets whether to update the dead time when the timer takes a sync signal.

The :cppmcpwm_new_operator will return a pointer to the allocated operator object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free operators in the MCPWM group, this function will return :cESP_ERR_NOT_FOUND error.2

On the contrary, calling :cppmcpwm_del_operator function will free the allocated operator object.

MCPWM Comparators

You can allocate a MCPWM comparator object by calling :cppmcpwm_new_comparator function, with a MCPWM operator handle and configuration structure :cppmcpwm_comparator_config_t as the parameter. The operator handle is created by :cppmcpwm_new_operator. The configuration structure is defined as:

  • :cppmcpwm_comparator_config_t::intr_priority sets the priority of the interrupt. If it is set to 0, the driver will allocate an interrupt with a default priority. Otherwise, the driver will use the given priority.
  • :cppmcpwm_comparator_config_t::update_cmp_on_tez sets whether to update the compare threshold when the timer counts to zero.
  • :cppmcpwm_comparator_config_t::update_cmp_on_tep sets whether to update the compare threshold when the timer counts to peak.
  • :cppmcpwm_comparator_config_t::update_cmp_on_sync sets whether to update the compare threshold when the timer takes a sync signal.

The :cppmcpwm_new_comparator will return a pointer to the allocated comparator object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free comparators in the MCPWM operator, this function will return :cESP_ERR_NOT_FOUND error.3

On the contrary, calling :cppmcpwm_del_comparator function will free the allocated comparator object.

MCPWM Generators

You can allocate a MCPWM generator object by calling :cppmcpwm_new_generator function, with a MCPWM operator handle and configuration structure :cppmcpwm_generator_config_t as the parameter. The operator handle is created by :cppmcpwm_new_operator. The configuration structure is defined as:

  • :cppmcpwm_generator_config_t::gen_gpio_num sets the GPIO number used by the generator.
  • :cppmcpwm_generator_config_t::invert_pwm sets whether to invert the PWM signal.
  • :cppmcpwm_generator_config_t::io_loop_back sets whether to enable the Loop-back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.
  • :cppmcpwm_generator_config_t::io_od_mode configures the PWM GPIO as open-drain output.
  • :cppmcpwm_generator_config_t::pull_up and :cppmcpwm_generator_config_t::pull_down controls whether to enable the internal pull-up and pull-down resistors accordingly.

The :cppmcpwm_new_generator will return a pointer to the allocated generator object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free generators in the MCPWM operator, this function will return :cESP_ERR_NOT_FOUND error.4

On the contrary, calling :cppmcpwm_del_generator function will free the allocated generator object.

MCPWM Faults

There are two types of faults: A fault signal reflected from the GPIO and a fault generated by software. To allocate a GPIO fault object, you can call :cppmcpwm_new_gpio_fault function, with configuration structure :cppmcpwm_gpio_fault_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_gpio_fault_config_t::group_id sets the MCPWM group ID. The ID should belong to [0, :cSOC_MCPWM_GROUPS - 1] range. Please note, GPIO fault located in different groups are totally independent, i.e. GPIO fault in group 0 can not be detected by the operator in group 1.
  • :cppmcpwm_gpio_fault_config_t::gpio_num sets the GPIO number used by the fault.
  • :cppmcpwm_gpio_fault_config_t::active_level sets the active level of the fault signal.
  • :cppmcpwm_gpio_fault_config_t::pull_up and :cppmcpwm_gpio_fault_config_t::pull_down set whether to pull up and/or pull down the GPIO internally.
  • :cppmcpwm_gpio_fault_config_t::io_loop_back sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.

The :cppmcpwm_new_gpio_fault will return a pointer to the allocated fault object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free GPIO faults in the MCPWM group, this function will return :cESP_ERR_NOT_FOUND error.5

Software fault object can be used to trigger a fault by calling a function :cppmcpwm_soft_fault_activate instead of waiting for a real fault signal on the GPIO. A software fault object can be allocated by calling :cppmcpwm_new_soft_fault function, with configuration structure :cppmcpwm_soft_fault_config_t as the parameter. Currently this configuration structure is left for future purpose. :cppmcpwm_new_soft_fault function will return a pointer to the allocated fault object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no memory left for the fault object, this function will return :cESP_ERR_NO_MEM error. Although the software fault and GPIO fault are of different types, but the returned fault handle is of the same type.

On the contrary, calling :cppmcpwm_del_fault function will free the allocated fault object, this function works for both software and GPIO fault.

MCPWM Sync Sources

The sync source is what can be used to synchronize the MCPWM timer and MCPWM capture timer. There're three types of sync sources: A sync source reflected from the GPIO, a sync source generated by software and a sync source generated by MCPWM timer event.

To allocate a GPIO sync source, you can call :cppmcpwm_new_gpio_sync_src function, with configuration structure :cppmcpwm_gpio_sync_src_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_gpio_sync_src_config_t::group_id sets the MCPWM group ID. The ID should belong to [0, :cSOC_MCPWM_GROUPS - 1] range. Please note, GPIO sync source located in different groups are totally independent, i.e. GPIO sync source in group 0 can not be detected by the timers in group 1.
  • :cppmcpwm_gpio_sync_src_config_t::gpio_num sets the GPIO number used by the sync source.
  • :cppmcpwm_gpio_sync_src_config_t::active_neg sets whether the sync signal is active on falling edges.
  • :cppmcpwm_gpio_sync_src_config_t::pull_up and :cppmcpwm_gpio_sync_src_config_t::pull_down set whether to pull up and/or pull down the GPIO internally.
  • :cppmcpwm_gpio_sync_src_config_t::io_loop_back sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.

The :cppmcpwm_new_gpio_sync_src will return a pointer to the allocated sync source object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no more free GPIO sync sources in the MCPWM group, this function will return :cESP_ERR_NOT_FOUND error.6

To allocate a Timer event sync source, you can call :cppmcpwm_new_timer_sync_src function, with configuration structure :cppmcpwm_timer_sync_src_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_timer_sync_src_config_t::timer_event specifies on what timer event to generate the sync signal.
  • :cppmcpwm_timer_sync_src_config_t::propagate_input_sync sets whether to propagate the input sync signal (i.e. the input sync signal will be routed to its sync output).

The :cppmcpwm_new_timer_sync_src will return a pointer to the allocated sync source object if the allocation succeeds. Otherwise, it will return error code. Specifically, if a sync source has been allocated from the same timer before, this function will return :cESP_ERR_INVALID_STATE error.

Last but not least, to allocate a software sync source, you can call :cppmcpwm_new_soft_sync_src function, with configuration structure :cppmcpwm_soft_sync_config_t as the parameter. Currently this configuration structure is left for future purpose. :cppmcpwm_new_soft_sync_src will return a pointer to the allocated sync source object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no memory left for the sync source object, this function will return :cESP_ERR_NO_MEM error. Please note, to make a software sync source take effect, don't forget to call :cppmcpwm_soft_sync_activate.

On the contrary, calling :cppmcpwm_del_sync_src function will free the allocated sync source object, this function works for all types of sync sources.

MCPWM Capture Timer and Channels

The MCPWM group has a dedicated timer which is used to capture the timestamp when specific event occurred. The capture timer is connected with several independent channels, each channel is assigned with a GPIO.

To allocate a capture timer, you can call :cppmcpwm_new_capture_timer function, with configuration structure :cppmcpwm_capture_timer_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_capture_timer_config_t::group_id sets the MCPWM group ID. The ID should belong to [0, :cSOC_MCPWM_GROUPS - 1] range.
  • :cppmcpwm_capture_timer_config_t::clk_src sets the clock source of the capture timer.

The :cppmcpwm_new_capture_timer will return a pointer to the allocated capture timer object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no free capture timer left in the MCPWM group, this function will return :cESP_ERR_NOT_FOUND error.7

Next, to allocate a capture channel, you can call :cppmcpwm_new_capture_channel function, with a capture timer handle and configuration structure :cppmcpwm_capture_channel_config_t as the parameter. The configuration structure is defined as:

  • :cppmcpwm_capture_channel_config_t::intr_priority sets the priority of the interrupt. If it is set to 0, the driver will allocate an interrupt with a default priority. Otherwise, the driver will use the given priority.
  • :cppmcpwm_capture_channel_config_t::gpio_num sets the GPIO number used by the capture channel.
  • :cppmcpwm_capture_channel_config_t::prescale sets the prescaler of the input signal.
  • :cppmcpwm_capture_channel_config_t::pos_edge and :cppmcpwm_capture_channel_config_t::neg_edge set whether to capture on the positive and/or falling edge of the input signal.
  • :cppmcpwm_capture_channel_config_t::pull_up and :cppmcpwm_capture_channel_config_t::pull_down set whether to pull up and/or pull down the GPIO internally.
  • :cppmcpwm_capture_channel_config_t::invert_cap_signal sets whether to invert the capture signal.
  • :cppmcpwm_capture_channel_config_t::io_loop_back sets whether to enable the loop back mode. It is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral.

The :cppmcpwm_new_capture_channel will return a pointer to the allocated capture channel object if the allocation succeeds. Otherwise, it will return error code. Specifically, when there are no free capture channel left in the capture timer, this function will return :cESP_ERR_NOT_FOUND error.

On the contrary, calling :cppmcpwm_del_capture_channel and :cppmcpwm_del_capture_timer will free the allocated capture channel and timer object accordingly.

MCPWM interrupt priority

MCPWM allows configuring interrupts separately for timer, operator, comparator, fault, and capture events. The interrupt priority is determined by the respective config_t::intr_priority. Additionally, events within the same MCPWM group share a common interrupt source. When registering multiple interrupt events, the interrupt priorities need to remain consistent.

Note

When registering multiple interrupt events within an MCPWM group, the driver will use the interrupt priority of the first registered event as the MCPWM group's interrupt priority.

Timer Operations and Events

Update Period

The timer period is initialized by the :cppmcpwm_timer_config_t::period_ticks parameter in :cppmcpwm_timer_config_t. You can update the period at runtime by calling :cppmcpwm_timer_set_period function. The new period will take effect based on how you set the :cppmcpwm_timer_config_t::update_period_on_empty and :cppmcpwm_timer_config_t::update_period_on_sync parameters in :cppmcpwm_timer_config_t. If none of them are set, the timer period will take effect immediately.

Register Timer Event Callbacks

The MCPWM timer can generate different events at runtime. If you have some function that should be called when particular event happens, you should hook your function to the interrupt service routine by calling :cppmcpwm_timer_register_event_callbacks. The callback function prototype is declared in :cppmcpwm_timer_event_cb_t. All supported event callbacks are listed in the :cppmcpwm_timer_event_callbacks_t:

  • :cppmcpwm_timer_event_callbacks_t::on_full sets callback function for timer when it counts to peak value.
  • :cppmcpwm_timer_event_callbacks_t::on_empty sets callback function for timer when it counts to zero.
  • :cppmcpwm_timer_event_callbacks_t::on_stop sets callback function for timer when it is stopped.

The callback functions above are called within the ISR context, so they should not attempt to block (e.g., make sure that only FreeRTOS APIs with ISR suffix is called within the function).

The parameter user_data of :cppmcpwm_timer_register_event_callbacks function is used to save user's own context, it will be passed to each callback function directly.

This function will lazy install interrupt service for the MCPWM timer without enabling it. It is only allowed to be called before before :cppmcpwm_timer_enable, otherwise the :cESP_ERR_INVALID_STATE error will be returned. See also Enable and Disable timer for more information.

Enable and Disable Timer

Before doing IO control to the timer, user needs to enable the timer first, by calling :cppmcpwm_timer_enable. Internally, this function will:

  • switch the timer state from init to enable.
  • enable the interrupt service if it has been lazy installed by :cppmcpwm_timer_register_event_callbacks.
  • acquire a proper power management lock if a specific clock source (e.g. PLL_160M clock) is selected. See also Power management for more information.

On the contrary, calling :cppmcpwm_timer_disable will put the timer driver back to init state, disable the interrupts service and release the power management lock.

Start and Stop Timer

The basic IO operation of a timer is to start and stop. Calling :cppmcpwm_timer_start_stop with different :cppmcpwm_timer_start_stop_cmd_t commands can start the timer immediately or stop the timer at a specific event. What're more, you can even start the timer for only one round, that means, the timer will count to peak value or zero, and then stop itself.

Connect Timer with Operator

The allocated MCPWM Timer should be connected with a MCPWM operator by calling :cppmcpwm_operator_connect_timer, so that the operator can take that timer as its time base, and generate the required PWM waves. Make sure the MCPWM timer and operator are in the same group, otherwise, this function will return :cESP_ERR_INVALID_ARG error.

Comparator Operations and Events

Register Event Callbacks

The MCPWM comparator can inform the user when the timer counter equals to the compare value. If you have some function that should be called when this event happens, you should hook your function to the interrupt service routine by calling :cppmcpwm_comparator_register_event_callbacks. The callback function prototype is declared in :cppmcpwm_compare_event_cb_t. All supported event callbacks are listed in the :cppmcpwm_comparator_event_callbacks_t:

  • :cppmcpwm_comparator_event_callbacks_t::on_reach sets callback function for comparator when the timer counter equals to the compare value.

The callback function will provide event specific data of type :cppmcpwm_compare_event_data_t to the user. The callback function is called within the ISR context, so is should not attempt to block (e.g., make sure that only FreeRTOS APIs with ISR suffix is called within the function).

The parameter user_data of :cppmcpwm_comparator_register_event_callbacks function is used to save user's own context, it will be passed to the callback function directly.

This function will lazy install interrupt service for the MCPWM comparator, whereas the service can only be removed in :cppmcpwm_del_comparator.

Set Compare Value

You can set the compare value for the MCPWM comparator at runtime by calling :cppmcpwm_comparator_set_compare_value. There're a few points to note:

  • New compare value might won't take effect immediately. The update time for the compare value is set by :cppmcpwm_comparator_config_t::update_cmp_on_tez or :cppmcpwm_comparator_config_t::update_cmp_on_tep or :cppmcpwm_comparator_config_t::update_cmp_on_sync.
  • Make sure the operator has connected to one MCPWM timer already by :cppmcpwm_operator_connect_timer. Otherwise, it will return error code :cESP_ERR_INVALID_STATE.
  • The compare value shouldn't exceed timer's count peak, otherwise, the compare event will never got triggered.

Generator Actions on Events

Set Generator Action on Timer Event

One generator can set multiple actions on different timer events, by calling :cppmcpwm_generator_set_actions_on_timer_event with variable number of action configurations. The action configuration is defined in :cppmcpwm_gen_timer_event_action_t:

  • :cppmcpwm_gen_timer_event_action_t::direction specific the timer direction. The supported directions are listed in :cppmcpwm_timer_direction_t.
  • :cppmcpwm_gen_timer_event_action_t::event specifies the timer event. The supported timer events are listed in :cppmcpwm_timer_event_t.
  • :cppmcpwm_gen_timer_event_action_t::action specifies the generator action to be taken. The supported actions are listed in :cppmcpwm_generator_action_t.

There's a helper macro :cMCPWM_GEN_TIMER_EVENT_ACTION to simplify the construction of a timer event action entry.

Please note, the argument list of :cppmcpwm_generator_set_actions_on_timer_event must be terminated by :cMCPWM_GEN_TIMER_EVENT_ACTION_END.

You can also set the timer action one by one by calling :cppmcpwm_generator_set_action_on_timer_event without varargs.

Set Generator Action on Compare Event

One generator can set multiple actions on different compare events, by calling :cppmcpwm_generator_set_actions_on_compare_event with variable number of action configurations. The action configuration is defined in :cppmcpwm_gen_compare_event_action_t:

  • :cppmcpwm_gen_compare_event_action_t::direction specific the timer direction. The supported directions are listed in :cppmcpwm_timer_direction_t.
  • :cppmcpwm_gen_compare_event_action_t::comparator specifies the comparator handle. See MCPWM Comparators for how to allocate a comparator.
  • :cppmcpwm_gen_compare_event_action_t::action specifies the generator action to be taken. The supported actions are listed in :cppmcpwm_generator_action_t.

There's a helper macro :cMCPWM_GEN_COMPARE_EVENT_ACTION to simplify the construction of a compare event action entry.

Please note, the argument list of :cppmcpwm_generator_set_actions_on_compare_event must be terminated by :cMCPWM_GEN_COMPARE_EVENT_ACTION_END.

You can also set the compare action one by one by calling :cppmcpwm_generator_set_action_on_compare_event without varargs.

Set Generator Action on Fault Event

One generator can set action on fault based trigger events, by calling :cppmcpwm_generator_set_action_on_fault_event with an action configurations. The action configuration is defined in :cppmcpwm_gen_fault_event_action_t:

  • :cppmcpwm_gen_fault_event_action_t::direction specifies the timer direction. The supported directions are listed in :cppmcpwm_timer_direction_t.
  • :cppmcpwm_gen_fault_event_action_t::fault specifies the fault used for the trigger. See MCPWM Faults for how to allocate a fault.
  • :cppmcpwm_gen_fault_event_action_t::action specifies the generator action to be taken. The supported actions are listed in :cppmcpwm_generator_action_t.

When no free trigger slot is left in the operator to which the generator belongs, this function will return the :cESP_ERR_NOT_FOUND error.8

The trigger only support GPOI fault. when the input is not a GPIO fault, this function will return the :cESP_ERR_NOT_SUPPORTED error.

There's a helper macro :cMCPWM_GEN_FAULT_EVENT_ACTION to simplify the construction of a trigger event action entry.

Please note, fault event does not have variadic function like :cppmcpwm_generator_set_actions_on_fault_event.

Set Generator Action on Sync Event

One generator can set action on sync based trigger events, by calling :cppmcpwm_generator_set_action_on_sync_event with an action configurations. The action configuration is defined in :cppmcpwm_gen_sync_event_action_t:

  • :cppmcpwm_gen_sync_event_action_t::direction specifies the timer direction. The supported directions are listed in :cppmcpwm_timer_direction_t.
  • :cppmcpwm_gen_sync_event_action_t::sync specifies the sync source used for the trigger. See MCPWM Sync Sources for how to allocate a sync source.
  • :cppmcpwm_gen_sync_event_action_t::action specifies the generator action to be taken. The supported actions are listed in :cppmcpwm_generator_action_t.

When no free trigger slot is left in the operator to which the generator belongs, this function will return the :cESP_ERR_NOT_FOUND error.9

The trigger only support one sync action, regardless of the kinds. When set sync actions more than once, this function will return the :cESP_ERR_INVALID_STATE error.

There's a helper macro :cMCPWM_GEN_SYNC_EVENT_ACTION to simplify the construction of a trigger event action entry.

Please note, sync event does not have variadic function like :cppmcpwm_generator_set_actions_on_sync_event.

Classical PWM Waveforms and Generator Configurations

This section will demonstrate the classical PWM waveforms that can be generated by the pair of the generators. The code snippet that is used to generate the waveforms is also provided below the diagram. Some general summary:

  • The Symmetric or Asymmetric of the waveforms are determined by the count mode of the MCPWM timer.
  • The active level of the waveform pair is determined by the level of the PWM with a smaller duty cycle.
  • The period of the PWM waveform is determined by the timer's period and count mode.
  • The duty cycle of the PWM waveform is determined by the generator's various action combinations.

Asymmetric Single Edge Active High

/../_static/diagrams/mcpwm/single_edge_asym_active_high.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_LOW)));
}

Asymmetric Single Edge Active Low

/../_static/diagrams/mcpwm/single_edge_asym_active_low.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_FULL, MCPWM_GEN_ACTION_LOW)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_FULL, MCPWM_GEN_ACTION_LOW)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_HIGH)));
}

Asymmetric Pulse Placement

/../_static/diagrams/mcpwm/pulse_placement_asym.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_COMPARE_EVENT_ACTION_END()));
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_TOGGLE),
                    MCPWM_GEN_TIMER_EVENT_ACTION_END()));
}

Asymmetric Dual Edge Active Low

/../_static/diagrams/mcpwm/dual_edge_asym_active_low.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, cmpb, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_COMPARE_EVENT_ACTION_END()));
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, MCPWM_TIMER_EVENT_FULL, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_TIMER_EVENT_ACTION_END()));
}

Symmetric Dual Edge Active Low

/../_static/diagrams/mcpwm/dual_edge_sym_active_low.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, cmpa, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_COMPARE_EVENT_ACTION_END()));
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, cmpb, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_COMPARE_EVENT_ACTION_END()));
}

Symmetric Dual Edge Complementary

/../_static/diagrams/mcpwm/dual_edge_sym_complementary.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, cmpa, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_COMPARE_EVENT_ACTION_END()));
    ESP_ERROR_CHECK(mcpwm_generator_set_actions_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_LOW),
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_DOWN, cmpb, MCPWM_GEN_ACTION_HIGH),
                    MCPWM_GEN_COMPARE_EVENT_ACTION_END()));
}

Dead Time

In power electronics, the rectifier and inverter are commonly used. This requires the use of rectifier bridge and inverter bridge. Each bridge arm has two power electronic devices, such as MOSFET, IGBT, etc. The two MOSFETs on the same arm can't conduct at the same time, otherwise there will be a short circuit. The fact is that, although the PWM wave shows it is turning off the switch, but the MOSFET still needs a small time window to make that happen. This requires an extra delay to be added to the existing PWM wave that generated by setting Generator Actions on Events.

The dead time driver works like a decorator. This is also reflected in the function parameters of :cppmcpwm_generator_set_dead_time, where it takes the primary generator handle (in_generator), and returns a new generator (out_generator) after applying the dead time. Please note, if the out_generator and in_generator are the same, it means you are adding the time delay to the PWM waveform in an "in-place" fashion. In turn, if the out_generator and in_generator are different, it means you are deriving a new PWM waveform from the existing in_generator.

Dead-time specific configuration is listed in the :cppmcpwm_dead_time_config_t structure:

  • :cppmcpwm_dead_time_config_t::posedge_delay_ticks and :cppmcpwm_dead_time_config_t::negedge_delay_ticks set the number of ticks to delay the PWM waveform on the rising and falling edge. Specifically, setting both of them to zero means to bypass the dead-time module. The resolution of the dead-time tick is the same to the timer that is connected with the operator by :cppmcpwm_operator_connect_timer.
  • :cppmcpwm_dead_time_config_t::invert_output: Whether to invert the signal after applying the dead-time, which can be used to control the delay edge polarity.

Warning

Due to the hardware limitation, one delay module (either posedge delay or negedge delay) can't be applied to multiple MCPWM generators at the same time. e.g. the following configuration is invalid:

mcpwm_dead_time_config_t dt_config = {
    .posedge_delay_ticks = 10,
};
// Set posedge delay to generator A
mcpwm_generator_set_dead_time(mcpwm_gen_a, mcpwm_gen_a, &dt_config);
// NOTE: This is invalid, you can't apply the posedge delay to another generator
mcpwm_generator_set_dead_time(mcpwm_gen_b, mcpwm_gen_b, &dt_config);

However, you can apply posedge delay to generator A and negedge delay to generator B. You can also set both posedge delay and negedge delay for generator A, while letting generator B bypass the dead time module.

Note

It is also possible to generate the required dead time by setting Generator Actions on Events, especially by controlling edge placement using different comparators. However, if the more classical edge delay-based dead time with polarity control is required, then the dead-time submodule should be used.

Classical PWM Waveforms and Dead Time Configurations

This section will demonstrate the classical PWM waveforms that can be generated by the dead-time submodule. The code snippet that is used to generate the waveforms is also provided below the diagram.

Active High Complementary

/../_static/diagrams/mcpwm/deadtime_active_high_complementary.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 50,
        .negedge_delay_ticks = 0
    };
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    dead_time_config.posedge_delay_ticks = 0;
    dead_time_config.negedge_delay_ticks = 100;
    dead_time_config.flags.invert_output = true;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, genb, &dead_time_config));
}

Active Low Complementary

/../_static/diagrams/mcpwm/deadtime_active_low_complementary.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 50,
        .negedge_delay_ticks = 0,
        .flags.invert_output = true
    };
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    dead_time_config.posedge_delay_ticks = 0;
    dead_time_config.negedge_delay_ticks = 100;
    dead_time_config.flags.invert_output = false;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, genb, &dead_time_config));
}

Active High

/../_static/diagrams/mcpwm/deadtime_active_high.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 50,
        .negedge_delay_ticks = 0,
    };
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    dead_time_config.posedge_delay_ticks = 0;
    dead_time_config.negedge_delay_ticks = 100;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, genb, &dead_time_config));
}

Active Low

/../_static/diagrams/mcpwm/deadtime_active_low.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 50,
        .negedge_delay_ticks = 0,
        .flags.invert_output = true
    };
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    dead_time_config.posedge_delay_ticks = 0;
    dead_time_config.negedge_delay_ticks = 100;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, genb, &dead_time_config));
}

Rising Delay on PWMA, Bypass deadtime for PWMB

/../_static/diagrams/mcpwm/deadtime_reda_bypassb.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 50,
        .negedge_delay_ticks = 0,
    };
    // apply deadtime to generator_a
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    // bypass deadtime module for generator_b
    dead_time_config.posedge_delay_ticks = 0;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(genb, genb, &dead_time_config));
}

Falling Delay on PWMB, Bypass deadtime for PWMA

/../_static/diagrams/mcpwm/deadtime_fedb_bypassa.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 0,
        .negedge_delay_ticks = 0,
    };
    // generator_a bypass the deadtime module (no delay)
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    // apply dead time to generator_b
    dead_time_config.negedge_delay_ticks = 50;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(genb, genb, &dead_time_config));

}

Rising and Falling Delay on PWMB, Bypass deadtime for PWMA

/../_static/diagrams/mcpwm/deadtime_redb_fedb_bypassa.json

static void gen_action_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb, mcpwm_cmpr_handle_t cmpa, mcpwm_cmpr_handle_t cmpb)
{
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(gena,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(gena,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpa, MCPWM_GEN_ACTION_LOW)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_timer_event(genb,
                    MCPWM_GEN_TIMER_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, MCPWM_TIMER_EVENT_EMPTY, MCPWM_GEN_ACTION_HIGH)));
    ESP_ERROR_CHECK(mcpwm_generator_set_action_on_compare_event(genb,
                    MCPWM_GEN_COMPARE_EVENT_ACTION(MCPWM_TIMER_DIRECTION_UP, cmpb, MCPWM_GEN_ACTION_LOW)));
}

static void dead_time_config(mcpwm_gen_handle_t gena, mcpwm_gen_handle_t genb)
{
    mcpwm_dead_time_config_t dead_time_config = {
        .posedge_delay_ticks = 0,
        .negedge_delay_ticks = 0,
    };
    // generator_a bypass the deadtime module (no delay)
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(gena, gena, &dead_time_config));
    // apply dead time on both edge for generator_b
    dead_time_config.negedge_delay_ticks = 50;
    dead_time_config.posedge_delay_ticks = 50;
    ESP_ERROR_CHECK(mcpwm_generator_set_dead_time(genb, genb, &dead_time_config));
}

Carrier Modulation

The MCPWM operator has a carrier submodule that can be used if galvanic isolation from the motor driver is required (e.g. isolated digital power application) by passing the PWM output signals through transformers. Any of PWM output signals may be at 100% duty and not changing whenever motor is required to run steady at the full load. Coupling of non alternating signals with a transformer is problematic, so the signals are modulated by the carrier submodule to create an AC waveform, to make the coupling possible.

To configure the carrier submodule, you can call :cppmcpwm_operator_apply_carrier, and provide configuration structure :cppmcpwm_carrier_config_t:

  • :cppmcpwm_carrier_config_t::clk_src sets the clock source of the carrier.
  • :cppmcpwm_carrier_config_t::frequency_hz indicates carrier frequency in Hz.
  • :cppmcpwm_carrier_config_t::duty_cycle indicates the duty cycle of the carrier. Note that, the supported choices of the duty cycle are discrete, the driver will search for the nearest one based on your configuration.
  • :cppmcpwm_carrier_config_t::first_pulse_duration_us indicates the duration of the first pulse in microseconds. The resolution of the first pulse duration is determined by the carrier frequency you set in the :cppmcpwm_carrier_config_t::frequency_hz. The first pulse duration can't be zero, and it has to be at least one period of the carrier. A longer pulse width can help conduct the inductance quicker.
  • :cppmcpwm_carrier_config_t::invert_before_modulate and :cppmcpwm_carrier_config_t::invert_after_modulate set whether to invert the carrier output before and after modulation.

Specifically, the carrier submodule can be disabled by calling :cppmcpwm_operator_apply_carrier with a NULL configuration.

Faults and Brake Actions

The MCPWM operator is able to sense external signals with information about failure of the motor, the power driver or any other device connected. These failure signals are encapsulated into MCPWM fault objects.

You should determine possible failure modes of the motor and what action should be performed on detection of a particular fault, e.g., drive all outputs low for a brushed motor, lock current state for a stepper motor, etc. Because of this action, the motor should be put into a safe state to reduce the likelihood of damage caused by the fault.

Set Operator Brake Mode on Fault

The way that MCPWM operator reacts to the fault is called Brake. The MCPWM operator can be configured to perform different brake modes for each fault object by calling :cppmcpwm_operator_set_brake_on_fault. Brake specific configuration is passed as a structure :cppmcpwm_brake_config_t:

  • :cppmcpwm_brake_config_t::fault set which fault that the operator should react to.
  • :cppmcpwm_brake_config_t::brake_mode set the brake mode that should be used for the fault. The supported brake modes are listed in the :cppmcpwm_operator_brake_mode_t. For :cppMCPWM_OPER_BRAKE_MODE_CBC mode, the operator will recover itself automatically as long as the fault disappears. You can specify the recovery time in :cppmcpwm_brake_config_t::cbc_recover_on_tez and :cppmcpwm_brake_config_t::cbc_recover_on_tep. For :cppMCPWM_OPER_BRAKE_MODE_OST mode, the operator can't recover even though the fault disappears. User has to call :cppmcpwm_operator_recover_from_fault to manually recover it.

Set Generator Action on Brake Event

One generator can set multiple actions on different brake events, by calling :cppmcpwm_generator_set_actions_on_brake_event with variable number of action configurations. The action configuration is defined in :cppmcpwm_gen_brake_event_action_t:

  • :cppmcpwm_gen_brake_event_action_t::direction specific the timer direction. The supported directions are listed in :cppmcpwm_timer_direction_t.
  • :cppmcpwm_gen_brake_event_action_t::brake_mode specifies the brake mode. The supported brake modes are listed in the :cppmcpwm_operator_brake_mode_t.
  • :cppmcpwm_gen_brake_event_action_t::action specifies the generator action to be taken. The supported actions are listed in :cppmcpwm_generator_action_t.

There's a helper macro :cMCPWM_GEN_BRAKE_EVENT_ACTION to simplify the construction of a brake event action entry.

Please note, the argument list of :cppmcpwm_generator_set_actions_on_brake_event must be terminated by :cMCPWM_GEN_BRAKE_EVENT_ACTION_END.

You can also set the brake action one by one by calling :cppmcpwm_generator_set_action_on_brake_event without varargs.

Register Fault Event Callbacks

The MCPWM fault detector can inform the user when it detects a valid fault or a fault signal disappears. If you have some function that should be called when such event happens, you should hook your function to the interrupt service routine by calling :cppmcpwm_fault_register_event_callbacks. The callback function prototype is declared in :cppmcpwm_fault_event_cb_t. All supported event callbacks are listed in the :cppmcpwm_fault_event_callbacks_t:

  • :cppmcpwm_fault_event_callbacks_t::on_fault_enter sets callback function that will be called when a fault is detected.
  • :cppmcpwm_fault_event_callbacks_t::on_fault_exit sets callback function that will be called when a fault is cleared.

The callback function is called within the ISR context, so is should not attempt to block (e.g., make sure that only FreeRTOS APIs with ISR suffix is called within the function).

The parameter user_data of :cppmcpwm_fault_register_event_callbacks function is used to save user's own context, it will be passed to the callback function directly.

This function will lazy install interrupt service for the MCPWM fault, whereas the service can only be removed in :cppmcpwm_del_fault.

Register Brake Event Callbacks

The MCPWM operator can inform the user when it going to take a brake action. If you have some function that should be called when this event happens, you should hook your function to the interrupt service routine by calling :cppmcpwm_operator_register_event_callbacks. The callback function prototype is declared in :cppmcpwm_brake_event_cb_t. All supported event callbacks are listed in the :cppmcpwm_operator_event_callbacks_t:

  • :cppmcpwm_operator_event_callbacks_t::on_brake_cbc sets callback function that will be called when the operator is going to take a CBC action.
  • :cppmcpwm_operator_event_callbacks_t::on_brake_ost sets callback function that will be called when the operator is going to take an OST action.

The callback function is called within the ISR context, so is should not attempt to block (e.g., make sure that only FreeRTOS APIs with ISR suffix is called within the function).

The parameter user_data of :cppmcpwm_operator_register_event_callbacks function is used to save user's own context, it will be passed to the callback function directly.

This function will lazy install interrupt service for the MCPWM operator, whereas the service can only be removed in :cppmcpwm_del_operator.

Generator Force Actions

Software can override generator output level at runtime, by calling :cppmcpwm_generator_set_force_level. The software force level always has a higher priority than other event actions set in e.g. :cppmcpwm_generator_set_actions_on_timer_event.

  • Set the level to -1 means to disable the force action, and the generator's output level will be controlled by the event actions again.
  • Set the hold_on to true, the force output level will keep alive, until it's removed by assigning level to -1.
  • Set the hole_on to false, the force output level will only be active for a short time, any upcoming event can override it.

Synchronization

When a sync signal is taken by the MCPWM timer, the timer will be forced into a predefined phase, where the phase is determined by count value and count direction. You can set the sync phase by calling :cppmcpwm_timer_set_phase_on_sync. The sync phase configuration is defined in :cppmcpwm_timer_sync_phase_config_t structure:

  • :cppmcpwm_timer_sync_phase_config_t::sync_src sets the sync signal source. See MCPWM Sync Sources for how to create a sync source object. Specifically, if this is set to NULL, the driver will disable the sync feature for the MCPWM timer.
  • :cppmcpwm_timer_sync_phase_config_t::count_value sets the count value to load when the sync signal is taken.
  • :cppmcpwm_timer_sync_phase_config_t::direction sets the count direction when the sync signal is taken.

Likewise, the MCPWM capture timer MCPWM Capture Timer can be synced as well. You can set the sync phase for the capture timer by calling :cppmcpwm_capture_timer_set_phase_on_sync. The sync phase configuration is defined in :cppmcpwm_capture_timer_sync_phase_config_t structure:

  • :cppmcpwm_capture_timer_sync_phase_config_t::sync_src sets the sync signal source. See MCPWM Sync Sources for how to create a sync source object. Specifically, if this is set to NULL, the driver will disable the sync feature for the MCPWM capture timer.
  • :cppmcpwm_capture_timer_sync_phase_config_t::count_value sets the count value to load when the sync signal is taken.
  • :cppmcpwm_capture_timer_sync_phase_config_t::direction sets the count direction when the sync signal is taken. Note that, different from MCPWM Timer, the capture timer can only support one count direction: :cppMCPWM_TIMER_DIRECTION_UP.

Sync Timers by GPIO

blockdiag {

GPIO -> Timer0, Timer1, Timer2;

}

static void example_setup_sync_strategy(mcpwm_timer_handle_t timers[])
{
    mcpwm_sync_handle_t gpio_sync_source = NULL;
    mcpwm_gpio_sync_src_config_t gpio_sync_config = {
        .group_id = 0,              // GPIO fault should be in the same group of the above timers
        .gpio_num = EXAMPLE_SYNC_GPIO,
        .flags.pull_down = true,
        .flags.active_neg = false,  // by default, a posedge pulse can trigger a sync event
    };
    ESP_ERROR_CHECK(mcpwm_new_gpio_sync_src(&gpio_sync_config, &gpio_sync_source));

    mcpwm_timer_sync_phase_config_t sync_phase_config = {
        .count_value = 0,                      // sync phase: target count value
        .direction = MCPWM_TIMER_DIRECTION_UP, // sync phase: count direction
        .sync_src = gpio_sync_source,          // sync source
    };
    for (int i = 0; i < 3; i++) {
        ESP_ERROR_CHECK(mcpwm_timer_set_phase_on_sync(timers[i], &sync_phase_config));
    }
}

Capture

The basic functionality of MCPWM capture is to record the time when any pulse edge of the capture signal turns active. Then you can get the pulse width and convert it into other physical quantities like distance or speed in the capture callback function. For example, in the BLDC (Brushless DC, see figure below) scenario, you can use the capture submodule to sense the rotor position from the Hall sensor.

MCPWM BLDC with Hall Sensor

MCPWM BLDC with Hall Sensor

The capture timer is usually connected with several capture channels, please refer to MCPWM Capture Timer and Channels for resource allocation.

Register Event Callbacks

The MCPWM capture channel can inform the user when there's a valid edge detected on the signal. You have to register a callback function to get the timer count value of the capture moment, by calling :cppmcpwm_capture_channel_register_event_callbacks. The callback function prototype is declared in :cppmcpwm_capture_event_cb_t. All supported capture callbacks are listed in the :cppmcpwm_capture_event_callbacks_t:

  • :cppmcpwm_capture_event_callbacks_t::on_cap sets callback function for the capture channel when a valid edge is detected.

The callback function will provide event specific data of type :cppmcpwm_capture_event_data_t, so that you can get the edge of the capture signal in :cppmcpwm_capture_event_data_t::cap_edge and the count value of that moment in :cppmcpwm_capture_event_data_t::cap_value. To convert the capture count into timestamp, you need to know the resolution of the capture timer by calling :cppmcpwm_capture_timer_get_resolution.

The callback function is called within the ISR context, so is should not attempt to block (e.g., make sure that only FreeRTOS APIs with ISR suffix is called within the function).

The parameter user_data of :cppmcpwm_capture_channel_register_event_callbacks function is used to save user's own context, it will be passed to the callback function directly.

This function will lazy install interrupt service for the MCPWM capture channel, whereas the service can only be removed in :cppmcpwm_del_capture_channel.

Enable and Disable Capture Channel

The capture channel is not enabled after allocation by :cppmcpwm_new_capture_channel. You should call :cppmcpwm_capture_channel_enable and :cppmcpwm_capture_channel_disable accordingly to enable or disable the channel. If the interrupt service is lazy installed during registering event callbacks for the channel in :cppmcpwm_capture_channel_register_event_callbacks, :cppmcpwm_capture_channel_enable will enable the interrupt service as well.

Enable and Disable Capture Timer

Before doing IO control to the capture timer, user needs to enable the timer first, by calling :cppmcpwm_capture_timer_enable. Internally, this function will:

  • switch the capture timer state from init to enable.
  • acquire a proper power management lock if a specific clock source (e.g. APB clock) is selected. See also Power management for more information.

On the contrary, calling :cppmcpwm_capture_timer_disable will put the timer driver back to init state, and release the power management lock.

Start and Stop Capture Timer

The basic IO operation of a capture timer is to start and stop. Calling :cppmcpwm_capture_timer_start can start the timer and calling :cppmcpwm_capture_timer_stop can stop the timer immediately.

Trigger a Software Capture Event

Sometime, the software also wants to trigger a "fake" capture event. The :cppmcpwm_capture_channel_trigger_soft_catch is provided for that purpose. Please note that, even though it's a "fake" capture event, it can still cause an interrupt, thus your capture event callback function will get invoked as well.

Power Management

When power management is enabled (i.e. CONFIG_PM_ENABLE is on), the system will adjust the PLL, APB frequency before going into light sleep, thus potentially changing the period of a MCPWM timers' counting step and leading to inaccurate time keeping.

However, the driver can prevent the system from changing APB frequency by acquiring a power management lock of type :cppESP_PM_APB_FREQ_MAX. Whenever the driver creates a MCPWM timer instance that has selected :cppMCPWM_TIMER_CLK_SRC_PLL160M as its clock source, the driver will guarantee that the power management lock is acquired when enable the timer by :cppmcpwm_timer_enable. Likewise, the driver releases the lock when :cppmcpwm_timer_disable is called for that timer.

Likewise, Whenever the driver creates a MCPWM capture timer instance that has selected :cppMCPWM_CAPTURE_CLK_SRC_APB as its clock source, the driver will guarantee that the power management lock is acquired when enable the timer by :cppmcpwm_capture_timer_enable. And will release the lock in :cppmcpwm_capture_timer_disable.

IRAM Safe

By default, the MCPWM interrupt will be deferred when the Cache is disabled for reasons like writing/erasing Flash. Thus the event callback functions will not get executed in time, which is not expected in a real-time application.

There's a Kconfig option CONFIG_MCPWM_ISR_IRAM_SAFE that will:

  1. Enable the interrupt being serviced even when cache is disabled
  2. Place all functions that used by the ISR into IRAM10
  3. Place driver object into DRAM (in case it's mapped to PSRAM by accident)

This will allow the interrupt to run while the cache is disabled but will come at the cost of increased IRAM consumption.

There is another Kconfig option CONFIG_MCPWM_CTRL_FUNC_IN_IRAM that can put commonly used IO control functions into IRAM as well. So, these functions can also be executable when the cache is disabled. These IO control functions are as follows:

  • :cppmcpwm_comparator_set_compare_value
  • :cppmcpwm_timer_set_period

Thread Safety

The factory functions like :cppmcpwm_new_timer are guaranteed to be thread safe by the driver, which means, you can call it from different RTOS tasks without protection by extra locks.

The following functions are allowed to run under ISR context, as the driver uses a critical section to prevent them being called concurrently in the task and ISR.

  • :cppmcpwm_comparator_set_compare_value
  • :cppmcpwm_timer_set_period

Other functions that are not related to Resource Allocation, are not thread safe. Thus, you should avoid calling them in different tasks without mutex protection.

Kconfig Options

  • CONFIG_MCPWM_ISR_IRAM_SAFE controls whether the default ISR handler can work when cache is disabled, see IRAM Safe for more information.
  • CONFIG_MCPWM_CTRL_FUNC_IN_IRAM controls where to place the MCPWM control functions (IRAM or flash), see IRAM Safe for more information.
  • CONFIG_MCPWM_ENABLE_DEBUG_LOG is used to enabled the debug log output. Enable this option will increase the firmware binary size.

Application Examples

  • Brushed DC motor speed control by PID algorithm: peripherals/mcpwm/mcpwm_bdc_speed_control
  • BLDC motor control with hall sensor feedback: peripherals/mcpwm/mcpwm_bldc_hall_control
  • Ultrasonic sensor (HC-SR04) distance measurement: peripherals/mcpwm/mcpwm_capture_hc_sr04
  • Servo motor angle control: peripherals/mcpwm/mcpwm_servo_control
  • MCPWM synchronization between timers: peripherals/mcpwm/mcpwm_sync

API Reference

inc/mcpwm_timer.inc

inc/mcpwm_oper.inc

inc/mcpwm_cmpr.inc

inc/mcpwm_gen.inc

inc/mcpwm_fault.inc

inc/mcpwm_sync.inc

inc/mcpwm_cap.inc

inc/components/driver/include/driver/mcpwm_types.inc

inc/components/hal/include/hal/mcpwm_types.inc

  1. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  2. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  3. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  4. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  5. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  6. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  7. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  8. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  9. Different ESP chip series might have different number of MCPWM resources (e.g. groups, timers, comparators, operators, generators and so on). Please refer to the [TRM] for details. The driver won't forbid you from applying for more MCPWM resources, but it will return error when there's no hardware resources available. Please always check the return value when doing Resource Allocation.↩

  10. Callback function and the sub-functions invoked by itself should also be placed in IRAM, users need to take care of this by themselves.↩