nRF52840 output the 32.768kHz clock on any GPIO in SPI Communication.

[rohit]

Dear Nordic Developer Zone,

I am working on MAX30003 ECG (https://datasheets.maximintegrated.com/en/ds/MAX30003.pdf)  with Nrf52840-DK. My sensor is work on the 32.768kHz external clock. 

but in Nrf I don't know which GPIO_PIN is assigned for that.

I visited below link but I unable to find solutions: 

https://devzone.nordicsemi.com/f/nordic-q-a/23474/nrf52832-fclk-pin/92210#92210

https://devzone.nordicsemi.com/f/nordic-q-a/15996/can-the-nrf52-output-the-32-768khz-clock-on-a-gpio

I am referring (SDK15.2 -PCA10056-spi code)

I have some questions about that:

1) Can I do the merging of timer and gpiote example code into SPI?

2) please give me detail about how to generate 32.768kHz clock ?

I have stuck  on below issue, 

https://maximsupport.microsoftcrmportals.com/en-us/knowledgebase/article/000096610

Thanks,

Rohit Patil

[haakonsh]

1) Yes of course.

2) You can't output the 32.768 clock on a GPIO. What you can do is share an external 32.768kHz clock with both the MAX30003 and the nRF52840 by setting the BYPASS and EXTERNAL bits in the LFCLKSRC register. 

[rohit]

Hi,

Thanks for the suggestion,

I am stuck in max30003 and nrf52840 because of I unable to read ECG_FIFO register value. it's showing zero.

(I try to  read INFO Register and other read register then  I got  default result as per max30003 datasheet ,surely my driver is working properly)

I discussed this issue  on MAXIM Forum.

maximsupport.microsoftcrmportals.com/.../000096610

As per his suggestion,  if I  check crystal oscillator of max30003 working or not ?, But it's working.

I got 32.768khz frequency on fclk pin of max30003.

Let me know,

1) is it any configuration required from nrf52840 side?

I am generating 16khz frequency on gpio pin using RTC example,

2) is it possible to generate 32.768khz using RTC? How to generate?

Kindly help me,

Thanks,

Rohit

[madblue]

if you are getting 32k on max30003 pin, why do you have to generate one?

from where you are getting that 32k clock?

max 30003 can't generate 32k clock by itself. i think your board have a 32k oscillator which is giving the clock?

some pictures of the board will be helpful

your spi might be working properly, but is your configurations for max30003 is correct ?