pwm driver + gpiote + ppi

[Stas]

Hello! I need to start a sequence of 26 pulses after getting low level signal on gpiote pin. I can do it in gpiote event handler but I need it most of the time so I want to use ppi for that here is my code:

nrf_ppi_channel_t ppi_channel;
nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0);

uint16_t /*const*/ seq_values[] ={1};
nrf_pwm_sequence_t const seq =
{
		.values.p_common = seq_values,
		.length          = NRF_PWM_VALUES_LENGTH(seq_values),
		.repeats         = 0,
		.end_delay       = 0
};

void in_data_handler (nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)

{
	//nrf_drv_pwm_simple_playback (&m_pwm0, &seq, 10, NRF_DRV_PWM_FLAG_STOP);
}

void HX711_init(uint8_t pin_number)
{
	nrf_drv_gpiote_init();
	nrf_drv_gpiote_in_config_t in_data_config = GPIOTE_CONFIG_IN_SENSE_HITOLO(true);
	in_data_config.pull = NRF_GPIO_PIN_PULLUP;
	nrf_drv_gpiote_in_init (HX_DATA, &in_data_config, in_data_handler);
	nrf_drv_gpiote_in_event_enable(HX_DATA, true);
	
			uint32_t err_code;
    nrf_drv_pwm_config_t const config0 =
    {
        .output_pins =
        {
            pin_number,                           // channel 0
            NRF_DRV_PWM_PIN_NOT_USED,             // channel 1
            NRF_DRV_PWM_PIN_NOT_USED,             // channel 2
            NRF_DRV_PWM_PIN_NOT_USED,             // channel 3
        },
        .base_clock   = NRF_PWM_CLK_2MHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 2,
        .load_mode    = NRF_PWM_LOAD_COMMON,
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    err_code = nrf_drv_pwm_init(&m_pwm0, &config0, NULL);
    APP_ERROR_CHECK(err_code);

	nrf_drv_ppi_init();
	
	nrf_drv_ppi_channel_alloc (&ppi_channel);
	nrf_drv_ppi_channel_assign (ppi_channel,nrf_drv_gpiote_in_event_addr_get(HX_DATA), nrf_drv_pwm_task_address_get(&m_pwm0, NRF_PWM_TASK_SEQSTART1));
	nrf_drv_ppi_channel_enable(ppi_channel);
}

The problem is I can't understand what kind of task should I use for ppi working like nrf_drv_pwm_simple_playback function

[Ole Bauck]

You can't use nrf_drv_pwm_simple_playback directly as this will trigger the start task at the end of the function.

You can use the function, just comment out start_playback. Then you should use the NRF_PWM_TASK_SEQSTART0 task as the PPI Event End Point (EEP).

[Stas]

Thank you. It's worked. As you told I commented out start_playback inside the nrf_drv_pwm_simple_playback function. and replace this function into my HX711_init function. but I have to point one pulse less in parameter of this playback function (in my case 25) otherwise I'll get 27 pulses. On other hand If I point 24 pulses I'll get 24 pulses. So actually I don't know how got for example 25 pulses (sometimes I need this amount of pulses).

[Stas]

I got it. For odd number we need NRF_PWM_TASK_SEQSTART1 task