I set up my PWM Driver like this:
nrf_drv_pwm_config_t const nrf_drv_pwm_config =
{
.output_pins =
{
BSP_LED_2 | NRF_DRV_PWM_PIN_INVERTED, // channel 0
NRF_DRV_PWM_PIN_NOT_USED, // channel 1
BSP_LED_3 | NRF_DRV_PWM_PIN_INVERTED, // channel 2
NRF_DRV_PWM_PIN_NOT_USED // channel 3
},
.irq_priority = APP_IRQ_PRIORITY_MID,
.base_clock = NRF_PWM_CLK_16MHz, // Need 250 clock to get 41kHz PWM that could have 50% duty cycle
.count_mode = NRF_PWM_MODE_UP,
.top_value = PWM_MAX_STEPS,
.load_mode = NRF_PWM_LOAD_GROUPED,
.step_mode = NRF_PWM_STEP_AUTO
};
And start the complex sequence like this:
static nrf_pwm_values_grouped_t final_pwm[2];
final_pwm[0].group_0 = PWM_MAX_STEPS;
final_pwm[0].group_1 = PWM_MAX_STEPS/2;
final_pwm[1].group_0 = PWM_MAX_STEPS;
final_pwm[1].group_1 = PWM_MAX_STEPS/2;
nrf_pwm_sequence_t const nrf_pwm_sequence =
{
.values.p_grouped = final_pwm,
.length = 4,
.repeats = 0,
.end_delay = 0
};
nrf_drv_pwm_simple_playback(&m_pwm, &nrf_pwm_sequence, 2, NRF_DRV_PWM_FLAG_LOOP|NRF_DRV_PWM_FLAG_SIGNAL_END_SEQ0);
But what happens is that the LED4 (pwm channel 2) gets full brightness and LED3 (pwm channel 0) gets no brightness. Then I realize that if I go from 0 to PWM_MAX_STEPS (62500), it goes up to maximum then back to zero again. Moreover, in the oscilloscope I checked that the frequency is actually close to 512Hz. It should be 256Hz, right?
F(pwm) = F(clk)/COUNTERTOP
In this case my F(clk) is 16MHz and COUNTERTOP should be PWM_MAX_STEPS which is 62500. Therefore F(pwm) should be 256Hz. In the o'scope it seems to be 512 as the period is close to 2ms. What am I missing here?
