Possible to create PWM phase delay

Question

Hi, guys. I'm using the PCA10056 and the SDK 15.3's BLE UART peripheral example. I'm working on a PWM controller using the mobile app. 
 
 I need to create a delayed PWM signal, just like the above picture. A pair (PWM 0, PWM 1 for instance) has the same frequency and duty cycle. 
 Is this possible to implement this without the NRF_DELAY function? I was curious whether the PWM modules can use other PWM modules as a trigger source 
 (PWM 0 triggers PWM 1 for instance) so that I can decrease the software codes. 
 If so, how should I modify the PWM code? 
 Lastly, how many PWM pairs are available?

haakonsh · Accepted Answer

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.

haakonsh · Answer

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.

Possible to create PWM phase delay

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