PWM not pulsing

RE: PWM not pulsing

Karlis — Fri, 26 Apr 2019 17:02:59 GMT

Its because seq_values array contains strucure nrf_pwm_values_individual_t, so inner brackets encloses structure values, but outer array items. With double brackets we are creating array with one item, which holds structure containing four variables. As example You can assign { {DUTY_CYCLE_1, 0, 0, 0} , {DUTY_CYCLE_2, 0, 0, 0}} and playback_count in nrf_drv_pwm_simple_playback defines how many times each DUTU_CYCLE are repeated before changing to next in array. Without double brackets Your compiler can misinterpret which value is which.

RE: PWM not pulsing

dmleone — Fri, 26 Apr 2019 16:34:12 GMT

I am perplexed why doing this worked

{ {DUTY_CYCLE, 0, 0, 0} }

I have been fighting this for like 2 days now almost ready to implement my own PWM. I am not a firmware expert by any means. Can yo uexplain why the double curly brakcets made it work and why you had to add them?

RE: PWM not pulsing

Karlis — Fri, 26 Apr 2019 16:08:39 GMT

For fast test I take sdk_config from examples/peripheral/pwm_driver/pca10040/blank/config and after fixing two lines about which armgcc complains Your code works as expected.

I only changed {DUTY_CYCLE, 0, 0, 0} to { {DUTY_CYCLE, 0, 0, 0} } and "void int main(void){" to "int main(void){"

ups I missed a point about app_pwm.h tested with nrf_drv_pwm.h

Sorry, I newer used app_pwm, but examples/peripheral/pwm_library looks absolutely different PWM initialisation and usage.

RE: PWM not pulsing

dmleone — Fri, 26 Apr 2019 15:27:09 GMT

I feel like there may not be a clock operating. All the example i see do the following

// Start clock for accurate frequencies
NRF_CLOCK->TASKS_HFCLKSTART = 1; 
// Wait for clock to start
while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) ;

However, i use LFCLK. Could me not doing that be an issue. If i do, ow to i enable both clocks, because i tried adding that intot he system and it made things worse.

Are there setting in the sdk_config file i need to set. Right now i have

NRFX_TIMER_ENABLED = 1; APP_TIMER_ENABLED = 1; and TIMER_ENABLED = 1

Am i getting conflicts?

RE: PWM not pulsing

Karlis — Fri, 26 Apr 2019 12:18:15 GMT

One idea I have is that You must increase playback_count in:

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

for example from 1 to 1000 ant test it, as I remember this defines how long pulses are generated.

For Looping manual says "To take advantage of the looping mechanism in the PWM peripheral, both sequences must be used (single sequence can be played back only once by the peripheral)", so I think curently Your sequence are played only once and for very short time.

Currently I can't test on my hardware, only maybe later, but I remember that value in my case is 2000.

RE: PWM not pulsing

dmleone — Fri, 26 Apr 2019 12:00:32 GMT

#define DUTY_CYCLE 50

RE: PWM not pulsing

Karlis — Fri, 26 Apr 2019 05:24:42 GMT

What is value of DUTY_CYCLE (on line 3) ?

If it set to 100% DC, then there is no pulses to see on scope only level change to high when turned on.