RE: nRF52 timer has no modulus?

Jan Rychter — Fri, 09 Dec 2016 10:33:40 GMT

Yes! Thank you — this seems to be what I was missing. While reading the specs I thought to myself: there is no way they could have designed an otherwise great chip with such a limitation.

I will have to figure out how exactly this clearing works out cycle-wise, but I'm very glad it's there. And yes, for PWM I will definitely use the PWM modules, I just used it as an example. At the moment I actually need specific timer periods.

RE: nRF52 timer has no modulus?

ovrebekk — Fri, 09 Dec 2016 09:11:00 GMT

Hi Jan

What you are probably missing is the SHORTS register, which allows you to enable a shortcut between any of the compare events and the clear task. With this enabled you can assign one of the CC registers to act as a reload register, and have the timer reset every time the value in the CC register is reached.

Codewise it would look something like this:

NRF_TIMER0->CC[3] = 1000;   
NRF_TIMER0->SHORTS = TIMER_SHORTS_COMPARE3_CLEAR_Msk;   
NRF_TIMER0->TASKS_START = 1;

As a side note, if what you need is PWM I would recommend using the dedicated PWM modules. They can also be configured with an arbitrary reload value, in the range 2-(2^15), and allow you to update the duty cycle directly from a RAM buffer without requiring MCU interaction.

Best regards
Torbjørn