MCPWM ESP32-S3 Function: mcpwm_set_duty_in_us (IDFGH-8151)

[misiek1994]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

IDF version.

4.4.2

Operating System used.

Linux

How did you build your project?

Eclipse IDE

If you are using Windows, please specify command line type.

No response

What is the expected behavior?

Function: mcpwm_set_duty_in_us should set pwm duty to specific value in us.

What is the actual behavior?

mcpwm_set_duty_in_us is not setting properly pwm.

Steps to reproduce.

mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM0A, SERVO_PULSE_GPIO_1);
mcpwm_config_t pwm_config = {
    .frequency = 50, // frequency = 50Hz, i.e. for every servo motor time period should be 20ms
    .cmpr_a = 0,     // duty cycle of PWMxA = 0
    .counter_mode = MCPWM_UP_COUNTER,
    .duty_mode = MCPWM_DUTY_MODE_1,
};
mcpwm_init(MCPWM_UNIT_0, MCPWM_TIMER_0, &pwm_config);

//doesnt work
ESP_ERROR_CHECK(mcpwm_set_duty_in_us(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_A, 10000));
//works!
ESP_ERROR_CHECK(mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_A, 50.0));

Build or installation Logs.

No response

More Information.

In function:

esp_err_t mcpwm_set_duty_in_us(mcpwm_unit_t mcpwm_num, mcpwm_timer_t timer_num, mcpwm_generator_t gen,                 uint32_t duty_in_us)
{
    //the driver currently always use the timer x for operator x
    const int op = timer_num;
    //the driver currently always use the comparator A for PWMxA output, and comparator B for PWMxB output
    const int cmp = gen;
    MCPWM_GEN_CHECK(mcpwm_num, timer_num, gen);
    mcpwm_hal_context_t *hal = &context[mcpwm_num].hal;

    mcpwm_critical_enter(mcpwm_num);
    int real_group_prescale = mcpwm_ll_group_get_clock_prescale(hal->dev);
    unsigned long int real_timer_clk_hz =
            SOC_MCPWM_BASE_CLK_HZ / real_group_prescale / mcpwm_ll_timer_get_clock_prescale(hal->dev, timer_num);
    mcpwm_ll_operator_set_compare_value(hal->dev, op, cmp, duty_in_us * real_timer_clk_hz / 1000000);
    mcpwm_ll_operator_enable_update_compare_on_tez(hal->dev, op, cmp, true);
    mcpwm_critical_exit(mcpwm_num);
    return ESP_OK;
}

Probably overflow in line: mcpwm_ll_operator_set_compare_value(hal->dev, op, cmp, duty_in_us * real_timer_clk_hz / 1000000);

Changing to: mcpwm_ll_operator_set_compare_value(hal->dev, op, cmp, real_timer_clk_hz / 1000000 * duty_in_us); fixed the problem, but there might be another when real_timer_clk_hz is not multiplication of 1MHz.

[suda-morris]

@misiek1994 Nice catch, I can also confirm this is a multiplication overflow. We should use uint64_t when converting us to compare ticks.