RE: Timer accuracy with softdevice

yinxu951 — Thu, 09 Feb 2023 06:45:23 GMT

sorry, TIMER2 should be TIMER1。 after enable the HFXO, the problem has been solved.

RE: Timer accuracy with softdevice

Einar Thorsrud — Wed, 08 Feb 2023 12:40:05 GMT

Hi,

The timer peripheral itself is not affected by the SoftDevice, and is completely independent. There is one thing to remember though, and that is that for the timer to be accurate, you need to request the HFXO so that it does not use the HFINT as clock source. If you don't, you will be using the (inaccurate) HFINT for the most part, except when there is radio activity, as the SoftDevice will enable the HFXO for those times.

As the SoftDevice does not impact the timer, there must be another issue. I do not see enough of you r code to get a full overview, but I see that you use shorts and PPI, which is independent of the CPU when configured, and thus also independent of the SoftDevice. However, I also see that you enable interrupt but I don't know what you are doing in the interrupt handler. A key point here is that the interrupt may be delayed if a higher priority SoftDevice interrupt is being processed at that time, so you should make sure to not depend on the timing of the interrupt (so don't do things like restarting timers etc. in an interrupt, instead this must be done with shorts or PPI in order to avoid such issues).

Lastly, I notice a few things worth mentioning. You write to both TIMER1 and TIMER2 registers, but I assume all should have been TIMER1? Also, you set the CC to 1000, and while that could be right, it seems wrong, as the counter counts from 0, and the clearing of the counter via a short also takes a clock cycle. This would give a consistent bias though, so it should not be related to the issue you are seeing.