[ERRATA] [nRF51] TIMER_SHORTS only works with timer interrupt enabled?

[Florian Echtler]

I'm using the PPI to generate a PWM signal on my nRF51822, and I've noticed that TIMER_SHORTS is never triggered unless the timer interrupt is also active. I had originally assumed that I don't need the interrupt at all when I use PPI, as the GPIO trigger works regardless of the interrupt state. The timer section in the RM (http://infocenter.nordicsemi.com/pdf/nRF51_RM_v3.0.1.pdf) doesn't mention anything, should this be an errata or note in the docs? I'm perfectly fine with having the interrupt enabled and doing nothing, but it looks like a potential error source...

Best, Florian

[Håkon Alseth]

Hi,

 

SHORTS shall work regardless of if the interrupt source is set in INTENSET or not.

Maybe you are affected by errata #73? http://infocenter.nordicsemi.com/pdf/nRF51822_pan_v3.3.pdf

Could you post the chip-markings of your device? Should be something similar to N51822 / QFAAH1 / 1515AA.

Best regards,

Håkon

[Florian Echtler]

Chip markings: NRF51822 QFAAH0 1745TF. #73 sounds plausible, thanks, I'll try the workaround (although it didn't look like I was loosing events, it's just the SHORTS->COMPARE0_CLEAR task that wasn't triggered. Or is that just the same internally?)

[Håkon Alseth]

That is considered the same internally. If the hardware does not detect the COMPARE0, the _CLEAR task will not occur. Let me know if the issue still appears after adding the workaround.

Cheers,

Håkon