Question about using nrf52 with 32k XTAL

[davidzweig]

Hello,

Quick question.. we are working on a board and running very low on GPIO pins. It would be helpful to remove the low-frequency (32k) XTAL, to recover those pins. The NRF52 will be driving an LED matrix, changing column at about 200-400Hz and using PWM for controlling brightness of individual LEDs.

My main question is, if we remove the 32k XTAL, there is a calibration proceedure that must run every 4s (IIRC). Is this operation blocking in any way? Will it interfere with the fairly strict timing requirements of the LED matrix (delays of 10ms or so when servicing the LED matrix would probably be noticeable when looking at the LEDs).

Alternatively, can we use any of the clever IO features (easyDMA?) to service the LED matrix without needing direct intervention by the processor?

Thanks for help.

David

[Simonr]

Hi David

The calibration procedure of the RC oscillator is not blocking, TASKS_CAL is called to start the process and when it's done you'll receive the EVENTS_DONE event, so this should not interfere with your application's timing requirements.

As per the PWM specification, change of polarity, duty-cycle, and base frequency is possible on every PWM period, so there should not be a large delay when setting the PWM duty cycle.

Best regards,

Simon

[davidzweig]

Thank you for excellent support. :-)