low power pulsewidth measurement: PPI & lfclk & S210 - some guidance needed

[WolfgangEbersbach]

Dear all,

I need to measure a pulse width on a GPIO pin which is in between 100mseconds and 7.2 seconds long without the use of "regular" timers due to low power requirements. I am pretty sure this can be done with PPI and the 32.768 kHz lfclock ( which runs anyway due to S210 use ). But I am simply lost in the examples and driver docs. Especially as I base my work on the bikepower ANT+ example which uses the board support package and app_button. Due to this I cannot copy-paste any code example as this always conflicts with something in the BSP or app_button.

Is there a hint which drivers / app_whatever to "implement" into existing examples that use BSP and app_button to connect a GPIO via PPI to a lsclock counter/timer ?

I "simply" need to start a lsclock counter by a GPIO pin interrupt (Low-High) and stop it by a high-low interrupt. Sadly I seem to be unable to do implement this simple task into the existing example code. As my max pulsewidth is > 10 seconds, a 16 bit counter is not sufficient @ 32.768 kHz clock. I am not sure if I can handle timer overflows due to the softdevice interrupting my program at any time.

Anyhow, the RealTimeCounter is 24 bits which is enough for my purpose. So, with RTC prescaler = 0 ( as used in app_button like it seems..) I could store the current TICK count at the low-high interrupt and then compare to the TICK count at the high-low interrupt and that's it. The counter roll-over case could be handled outside the ISR.

Just: How to do it ?

Any help like "remove this driver, add that one, re-use this timer.. " is very appreciated.

Thanks a lot, Wolfgang

[WolfgangEbersbach]

Ole, the SoftDevice IS enabled and works. I do get ANT+ messages "on air". Just, the GPIO ISR never fires and the reason is that sd_nvic_EnableIRQ does return an error ( I am still not able to get the return values as the debugger insists that the variable assigned to it ( usually err_code ) is "not in scope". So we are back to the original where nrf_drv_gpiote_in_init also returned an error. If you could get me some advice on how to get the returned error code, we likely could track it down better. I use Keil V5.17 and your SDK version 10 (not the Keil packs) and the ant_bpwr_tx_wheel_torque_button_s210 example code.

Aaaah, so you say I need to enable the softdevice FIRST and THEN call sd_nvic_EnableIRQ() , correct ? OK, up to now I set up the softdevice last in my main().

Nope, makes no difference. APP_ERROR_CHECK does never return if it checks the return value of sd_nvic_EnableIRQ() , no matter if I call sd_nvic_EnableIRQ() before or after softdevice setup...

according to the sofdevice documentation there is only two possible errors for sd_nvic_EnableIRQ: Interrupt not available or priority not allowed... I have the feeling "something else" is using this interrupt already.

This may help tracking it down:

GPIO20 ( which is what I used here ) looks good:

[RK]

So if the two errors are 'interrupt not available' and 'priority not allowed', since you know GPIOTE is an available interrupt, it must be an invalid priority. Did you set the priority of the GPIOTE interrupt (if it's in the rest of the answer somewhere I apologise, I looked but didn't find it). If you didn't set it, it's by default 0 which isn't allowed.

[WolfgangEbersbach]

RK, thanks for the comment. 1) I do not know which of the two errors is returned. 2) I do not know if GPIOTE is an available interrupt. It is by the softdevice documentation, but maybe app_twi uses it ? 3) No, I did not set the interrupt priority, at least not that I know. I'll try to find out how to set the priority and report back here.