NPM1304 Watchdog Timer & Power Cycle

[arif__anwar]

Hi Support

We are in the process of integrating the NPM1304 into a small battery (55mAh) wearable device. I am finding it hard to figure out section 7.3.2

regarding the Watchdog. We would like the Watchdog timer expiration to generate a power cycle, but cannot figure out which registers need to

be set for this or how the hardware needs to be set up. 

1) We have a single button in the product, which enables the user to scroll through modes (short presses), can the same button be be used to

generate the power cycle for a 10s press? Would you have application schematics we could follow?

2) can the watchdog pat cycle be greater than a day, and can this be achieved when in Sleep Mode?

Any suggestions would be appreciated.

[Vidar Berg]

Hello,

If you're using the nRF Connect SDK, I would recommend considering using the Zephyr watchdog driver to control it. Alternatively you can look at the driver implementation linked below and use it as a reference. 

In devicetree:

npm1304_pmic: pmic@3 {
	compatible = "nordic,npm1304";
	
	npm1304_wdt: watchdog {
	compatible = "nordic,npm1304-wdt";
	};
};

Zephyr WDT sample:

https://github.com/nrfconnect/sdk-zephyr/tree/main/samples/drivers/watchdog

npm1304 wdt driver implementation:

https://github.com/nrfconnect/sdk-zephyr/blob/main/drivers/watchdog/wdt_npm13xx.c 

arif__anwar said:

1) We have a single button in the product, which enables the user to scroll through modes (short presses), can the same button be be used to

generate the power cycle for a 10s press? Would you have application schematics we could follow

The button interrupt would have to be handled on the MCU to trigger other modes which are not supported by the PMIC. Seems like you should still be able to trigger a power cycle:

arif__anwar said:

2) can the watchdog pat cycle be greater than a day, and can this be achieved when in Sleep Mode?

Yes, largest timeout is 74.5 hours:

but the WD cannot be used in ship or hibernate mode: 

Best regards,

Vidar

[arif__anwar]

Morning Vidar

Apologies for the late reply, I've been busy with another project which took up more time than I expected. Just to clarify

1) Functions not supported by the PMIC will be serviced in firmware, my main requirement is that the PMIC reset power to the application hardware IF the watchdog is not serviced (ie MCU has crashed or hung). Is this something the 1304 can do without CPU intervention?

Arif

[Vidar Berg]

Hi Arif,

Yes, in the case of a crash, your application should stop reloading the WDT which will cause it to time out and reset the MCU.

[arif__anwar]

Morning Vidar

Thanks for clarification. Really appreciate your help.