NRF52840 SAADC configuration with easyDMA interrupt after x samplings

[ziv123]

hello Nordic

i am using nrf 52840 dev kit, sdk 16.0

i want to make a sampling of 2 channels at 32MHz rate. the data shell be passed to RAM via easyDMA, after every 4 samplings i whish to raise an interrupt so i can average the readings from each channel. 

(as i understand if i do oversampling and burst then it reads one channel several time and averaging and then do the same for the other channel, this solution is not good for me because i need to compare the reading of the 2 channels with each other so the data needs to be collected as simultaneously as possible) 

what the optimal way to achieve the above ?

also, if i use app_timer as the RTC timer for the saadc, does it involves the CPU ?, can it use ppi? (the name "app" makes me suspicious :) ) and is it a good solution for 32MHz sampling rate or is it to fit ?

best regards

Ziv

[haakonsh]

Do you mean kHz or MHz?
I ask because the SAADC has a max sample rate of 200ksps.

[ziv123]

also, does the timer configured as default in the saadc example is the HFCLOCK ?

static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(0);

basically, since i  need sampling at accurate 32KHz, the LOW FCLOCK is not suck a good solution cause according to data sheet it counts 32.768KHz and not 32.000KHz