RE: 32.768 KHz Clock out on nrf52 GPIO

Kazi Afroza Sultana — Thu, 07 Jul 2022 17:48:37 GMT

Hello,

1. Is it possible to output 32.768 KHz clock on a GPIO of nrf52 device ? In our design we use two crystal oscillators which are connected to nrf52840 : i) 32 MHz and ii) 32.768KHz

Hello ,

it is not possible to get output clock of 32.768 KHZ on a GPIO pin on nRF52 device (https://devzone.nordicsemi.com/f/nordic-q-a/36554/nrf52840-outputing-lfclock-on-a-pin/140662#140662). 32 MHZ is the crystal for high frequency and 32.768 KHZ is the low frequency crystal which is optional but it is recommended to be in the part of design for less power consumption. Even though it's not possible to get the output of crystal on GPIO pin, you can use a TIMER and PPI to GPIOTE and can get only half of the LFCLK (16.38 KHz) in GPIO. One toggle of 1 TICK on GPIO is converted to two RTC TICK (which converts to one cycle on GPIO). You can see this link : https://devzone.nordicsemi.com/f/nordic-q-a/364/lfclk-32khz-on-a-gpio-pin-for-precision-measurement/1905#1905

2. What is PCLK32KI shown in Clock control Figure 20 of https://infocenter.nordicsemi.com/pdf/nRF52840_PS_v1.1.pdf ? How is it accessible, please share code snippet.

This is output of the 32.768 KHZ low frequency crystal. But it is internally controlled inside IC. There is no option to get an output on this GPIO. pin.

Thanks.

Best Regards,

Kazi Afroza Sultana