pwm.rst

.. index::
    single: PWM

PWM

Note

The Datasheet specifies PWM channels 0 and 1. The Raspberry Pi has pins for PWM channels 1 and 2, you just need to add one.

Macros

.. macro:: PWM_OFFSET

    ::

        0x20C000

    This macro defines the offset at which the PWM registers are located from
    the peripheral base.

.. macro:: PWM_SIZE

    ::

        0x24

    This macro holds the size of the I2C registers which needs to be mapped.

.. macro:: RNG_CHANNEL0

.. macro:: DAT_CHANNEL0

.. macro:: RNG_CHANNEL1

.. macro:: DAT_CHANNEL1

    ::

        #define RNG_CHANNEL0    PWM->RNG1
        #define DAT_CHANNEL0    PWM->DAT1
        #define RNG_CHANNEL1    PWM->RNG2
        #define DAT_CHANNEL1    PWM->DAT2

    To prevent confusion (because the Datasheet_ calls the PWM channels 1 and 2
    and the Raspberry Pi 0 and 1) the values of the registers which need to be
    used "on the fly" are :code;`defined` from 2 to 1 and from 1 to 0.

Configuration Macros

:macro:`PWM_CTL_MODE_PWM`	Use PWM mode
:macro:`PWM_CTL_MODE_SERIALISER`	Use serialiser mode
:macro:`PWM_RPTL_STOP`	If serialiser mode: Transmission stops when fifo empty
:macro:`PWM_RPTL_REPEAT`	If serialiser mode: Repeat last data when fifo empty
:macro:`PWM_SBIT_LOW`	Output low when no transmission active
:macro:`PWM_SBIT_HIGH`	Output high when no transmission active
:macro:`PWM_POLA_DEFAULT`	Polarity is default
:macro:`PWM_POLA_INVERTED`	Polarity is innverted
:macro:`PWM_USEF_DATA`	Data register is transmitted
:macro:`PWM_USEF_FIFO`	Data from fifo is transmitted
:macro:`PWM_MSEN_PWMALGORITHM`	Use PWM algorithm
:macro:`PWM_MSEN_MSRATIO`	Use MS ratio

Registers

.. var:: volatile uint32_t *pwm_base_ptr

    This pointer points, when mapped, to the base of the PWM registers.

.. type:: struct pwm_register_map

    This struct maps the registers of the PWM.
    The names of the struct members correspond to the registers
    from the Datasheet_::

        struct pwm_register_map {
            uint32_t CTL;
            uint32_t STA;
            uint32_t DMAC;
            uint32_t: 32;
            uint32_t RNG1;
            uint32_t DAT1;
            uint32_t FIF1;
            uint32_t: 32;
            uint32_t RNG2;
            uint32_t DAT2;
        };

.. macro:: PWM

    ::

        #define PWM ((volatile struct pwm_register_map *)pwm_base_ptr)

    By using this macro, the registers of the PWM can be accessed like this
    :code:`PWM->RNG1`.

Enums

.. type:: pwm_channel_t

    This enum holds the values distinguishing PWM channel 0 and 1::

        typedef enum {
            PWM_CHANNEL0, PWM_CHANNEL1
        } pwm_channel_t;

Structs

.. type:: pwm_channel_config_t

    This struct is used to configure a PWM channel::

        typedef struct {
            union {
                struct {
                    uint32_t: 1;
                    uint32_t mode: 1;
                    uint32_t rptl: 1;
                    uint32_t sbit: 1;
                    uint32_t pola: 1;
                    uint32_t usef: 1;
                    uint32_t: 1;
                    uint32_t msen: 1;
                };
                uint32_t ctl_register;
            };
            unsigned int divisor;
            uint32_t range;
        } pwm_channel_config_t;

    .. member:: uint32_t ctl_register

        This member can be directly edited by the anonymous struct inside
        this union. This register maps directly to the :code:`CTL` register,
        with some offset for PWM 1. The settings of this register are described
        in the `Macros`_.

    .. member:: unsigned int divisor

        The divisor which is passed to the :doc:`clock_manager`.

    .. member:: uint32_t range

        The range to which the PWM counter counts before it starts over.

Functions

.. function:: uint32_t * pwm_map(void)

    This function maps the PWM registers. It calls :func:`peripheral_map` with
    the values :macro:`PWM_OFFSET` and :macro:`PWM_SIZE`.

.. function:: void pwm_unmap(void)

    This function unmaps the PWM registers.

.. function:: void pwm_configure(pwm_channel_t channel, pwm_channel_config_t *config)

    This function configures :type:`pwm_channel_t` :code:`channel` with a
    :type:`pwm_channel_config_t` pointed to by :code:`config`.

.. function:: void pwm_enable(pwm_channel_t channel)

    This function enables :type:`pwm_channel_t` :code:`channel`.

.. function:: void pwm_disable(pwm_channel_t channel)

    This function disables :type:`pwm_channel_t` :code:`channnel`.