RE: Configure PWM driver to have similar behaviour as an Arduino analogWrite()

Edvin — Wed, 08 Jan 2020 15:09:36 GMT

Yes, it seems you got it about right.

If you are looking for a simpler PWM, I would recommend that you peek into the "pwm_library" example as well. There you will basically have a function called app_pwm_channel_duty_set(), which takes a number from 0 to 100% where 0 would be GND and 100 would be VDD. This function is also easy to modify to use 1/1000 instead of 1/100 if you need higher accuracy.

Best regards,

Edvin

RE: Configure PWM driver to have similar behaviour as an Arduino analogWrite()

Or — Wed, 08 Jan 2020 12:41:52 GMT

Following code seems to be doing the job:

nrf_drv_pwm_config_t config =
    {
        // These are the common configuration options we use for all PWM
        // instances.
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .count_mode   = NRF_PWM_MODE_UP,
        .step_mode    = NRF_PWM_STEP_AUTO,
    };

config.output_pins[0] = BSP_LED_0 | NRF_DRV_PWM_PIN_INVERTED;
config.output_pins[1] = NRF_DRV_PWM_PIN_NOT_USED;
config.output_pins[2] = NRF_DRV_PWM_PIN_NOT_USED;
config.output_pins[3] = NRF_DRV_PWM_PIN_NOT_USED;
config.base_clock     = NRF_PWM_CLK_125kHz;
config.top_value      = 255;
config.load_mode      = NRF_PWM_LOAD_COMMON;
RETURN_ON_ERROR(nrf_drv_pwm_init(&m_pwm0, &config, NULL));

// This array cannot be allocated on stack (hence "static") and it must
// be in RAM (hence no "const", though its content is not changed).
static nrf_pwm_values_common_t /*const*/ pwm0_seq_values[1];
pwm0_seq_values[0] = value; // ** this is the value passed to "analogWrite()" **

nrf_pwm_sequence_t const pwm0_seq =
{
	.values.p_common  = pwm0_seq_values,
	.length           = NRF_PWM_VALUES_LENGTH(pwm0_seq_values),
	.repeats          = 1,
	.end_delay        = 0
};

nrf_drv_pwm_simple_playback(&m_pwm0, &pwm0_seq, 1, NRF_DRV_PWM_FLAG_LOOP);