How to use PWM Sequence for complex LED control ( n times dimming and then stop )

RE: Is there TIMER + GPIOTE + PPI exampe ?

bluemountain — Mon, 16 Jun 2025 13:38:43 GMT

Thanks,.

I replaced NRFX_PWM_PIN_NOT_USED with NRF_PWM_PIN_NOT_CONNECTED. to fix a compile error. After that, I compiled and flashed the code onto nRF52840. The LED dimming works great, but it keeps dimming continuously without stop.

(void)nrfx_pwm_complex_playback(&pwm_instance, &led_on_seq, &led_off_seq, 1,
NRFX_PWM_FLAG_LOOP);
The fourth parameter '1' is the playback count, which should go into the LOOP register.
From what I understand, this should control the number of dimming cycles. So, the LED should stop after one dimming cycle.
And if I change the value to 3, the LED should dim three times and then stop.

However, no matter what number I use, the LED never stops dimming.

Could you please check the code and teach me how to correctly specify the number of dimming cycles?

-->

After I change NRFX_PWM_FLAG_LOOP to NRFX_PWM_FLAG_STOP, LED dimming stops.
I'll study the code and check the register settings in detail.

I'll open new ticket when I have another question.
Please close this ticket.

Note.
The title of this ticket does not match with the contents. So, I changed it.

Best Regards,

RE: Is there TIMER + GPIOTE + PPI exampe ?

Vidar Berg — Mon, 16 Jun 2025 07:02:40 GMT

Please try with the sample posted here: RE: Softblink in NCS/Zephyr

RE: Is there TIMER + GPIOTE + PPI exampe ?

bluemountain — Sat, 14 Jun 2025 03:55:24 GMT

Hi Turbo,

As your suggestion, I've tried to make the LED control with PWM. But, I couldn't make it.
I had used PWM and sequence, but it just show about 1s ON without any blinking.

Can you see the code below and what I got wrong ?

This is what I want to do

* for ( n_blink ) { // 'n_blink' for number of visual toggle

* for ( n_fast_blink ) { // 'fast' for LED bright control

* led on : t_fast_on_us us // t_fast_on_us + t_fast_off_us makes 't_on' since LED toggles very fast

* led off : t_fast_off_us us

* }

* led off : t_off_us us // 't_off'

* }

led_blinkx2_conf(

/* n_f_blinks */ 10,

/* t_f_on_us */ 100*1000,

/* t_f_off_us */ 100*1000,

/* n_blink */ 5,

/* t_off_us */ 200*1000

);

Settings

Read-back
NRF_PWM0->PSEL.OUT[0] = 0x0000000D 13
NRF_PWM0->PSEL.OUT[1] = 0xFFFFFFC0 -64
NRF_PWM0->PSEL.OUT[2] = 0xFFFFFFC0 -64
NRF_PWM0->PSEL.OUT[3] = 0xFFFFFFC0 -64
NRF_PWM0->MODE = 0x00000000 0
NRF_PWM0->PRESCALER = 0x00000007 7
NRF_PWM0->DECODER = 0x00000000 0

NRF_PWM0->COUNTERTOP = 0x000061A8 25000
NRF_PWM0->SEQ[0].PTR = 0x2000105A 536875098
NRF_PWM0->SEQ[0].CNT = 0x0000000A 10
NRF_PWM0->SEQ[0].REFRESH = 0x00000002 2
NRF_PWM0->SEQ[0].ENDDELAY = 0x000061A8 25000
NRF_PWM0->LOOP = 0x00000004 4
NRF_PWM0->ENABLE = 0x00000001 1
PWM_SEQ
PWM_SEQ [ 000 ] = 0x000030D4 12500
PWM_SEQ [ 001 ] = 0x000030D4 12500
PWM_SEQ [ 002 ] = 0x000030D4 12500
PWM_SEQ [ 003 ] = 0x000030D4 12500
PWM_SEQ [ 004 ] = 0x000030D4 12500
PWM_SEQ [ 005 ] = 0x000030D4 12500
PWM_SEQ [ 006 ] = 0x000030D4 12500
PWM_SEQ [ 007 ] = 0x000030D4 12500
PWM_SEQ [ 008 ] = 0x000030D4 12500
PWM_SEQ [ 009 ] = 0x000030D4 12500
PWM_SEQ [ 010 ] = 0x000030D4 12500
PWM_SEQ [ 011 ] = 0x000030D4 12500
PWM_SEQ [ 012 ] = 0x000030D4 12500
PWM_SEQ [ 013 ] = 0x000030D4 12500
PWM_SEQ [ 014 ] = 0x000030D4 12500
PWM_SEQ [ 015 ] = 0x000030D4 12500
PWM_SEQ [ 016 ] = 0x000030D4 12500
PWM_SEQ [ 017 ] = 0x000030D4 12500
PWM_SEQ [ 018 ] = 0x000030D4 12500
PWM_SEQ [ 019 ] = 0x000030D4 12500

What I got

LED keeps blinking about 5Hz.

But it never stops.

RE: Is there TIMER + GPIOTE + PPI exampe ?

Turbo J — Thu, 12 Jun 2025 13:22:37 GMT

You could just use a PWM peripherial for this task. Should be simple.

If you used the RTC timer, you would achieve a lot less current consumtion in the off time - because the HF(int) oscillator can sleep. It can't when TIMER or PWM was active.