Possible to create PWM phase delay

RE: Possible to create PWM phase delay

Matthew K — Sat, 04 Apr 2020 07:21:10 GMT

Apologize for my late response; due to the recent pandemic, I left my gadgets outside :/ I'll try to share this someday.

RE: Possible to create PWM phase delay

samuel.zetterlund — Tue, 03 Mar 2020 12:24:34 GMT

Hi Matthew. I have the exact same problem. I need to trigger output with the same frequency on three channels in direct sequence. Could you please share some code snippets explaining how you set this up?

Kind regards,

Samuel

RE: Possible to create PWM phase delay

haakonsh — Thu, 27 Jun 2019 13:51:20 GMT

See the PPI Example, it uses 3 TIMERs.

Again, you can connect any EVENT to any TASK, regardless of what peripherals are used.

f.ex. The SAADC's EVENTS_END can be connected to a SPIM's TASKS_START. By connecting a TIMER's EVENTS_COMPARE to the SAADC's TASKS_SAMPLE, you've set up a self-driven ADC sampler that streams data over SPI, all without invoking the CPU.

That's the power of PPI and EasyDMA.

RE: Possible to create PWM phase delay

Matthew K — Thu, 27 Jun 2019 06:32:15 GMT

[quote userid="13562" url="~/f/nordic-q-a/48884/possible-to-create-pwm-phase-delay/194245"]When this is set up you correctly the second PWM will start after a predetermined delay, without invoking the CPU. [/quote]

Wonderful! That is what I needed.

Can I connect the TIMER — Timer/counter's compare match event (EVENTS_COMPARE[n]) with the SDK 15's timer example?

It would be great if there are examples which I can refer to.

RE: Possible to create PWM phase delay

haakonsh — Mon, 24 Jun 2019 08:16:39 GMT

You'll need to use PPI — Programmable peripheral interconnect and connect a TIMER — Timer/counter's compare match event (EVENTS_COMPARE[n]) to the second PWM's sequence start task (TASKS_SEQSTART[n]). I also suggest that you connect the compare match event to the TIMER's stop and clear tasks(TASKS_CLEAR, TASKS_STOP) via the SHORTS register or appropriate TIMER API calls.

You can use the first PWM's sequence started event to trigger the TIMER's start task (TASKS_START).

When this is set up you correctly the second PWM will start after a predetermined delay, without invoking the CPU.

The nRF52840 has four PWM peripherals instances, each instance has four outputs. In your case, you've got two sets of PWM frequencies and you will, therefore, need two PWM instances with two outputs each.

You can also create additional PWM signals with a TIMER and the GPIOTE peripheral.