Minimal common reset between nRF9160 and nRF52832

RE: Minimal common reset between nRF9160 and nRF52832

Kenneth — Wed, 20 Jul 2022 12:49:12 GMT

The reset pin is not neccesay no, but the reset pin should be available somehow if you by accident enable it and it is pulled low by some circuitry, in that case you need to pull it high somehow to ensure you can program and/or debug te nRF over the SWD interface.

But seen from the j-link you only need the 4 pins in question.

Best regards,
Kenneth

RE: Minimal common reset between nRF9160 and nRF52832

okwestern — Wed, 20 Jul 2022 12:05:27 GMT

Is the reset pin needed for programming (nRF9160, nRF52832 and nRF52840)?

Would the minimal VCC, GND, SWDIO, SWDCLK be enough, and I would loose no functionality?

RE: Minimal common reset between nRF9160 and nRF52832

Kenneth — Mon, 18 Jul 2022 13:28:36 GMT

Ah, I can see that now, but based on this you will need to solve this in a different way than connecting the two pins together directly. You may potentially tail-chain them in some way, e.g. that the switch is only connected to the nRESET is of the nRF9160, and then after reset the nRF9160 can reset the nRF52832 through a pin of it's own.

Kenneth

RE: Minimal common reset between nRF9160 and nRF52832

okwestern — Mon, 18 Jul 2022 12:23:42 GMT

The 2.2V is the datasheet value of nRF9160 reset pin when internally pulled up. It's not my choice of power domain 🙂

RE: Minimal common reset between nRF9160 and nRF52832

Kenneth — Mon, 18 Jul 2022 12:10:46 GMT

Hello.

It looks to me that you have different power domains here (e.g. you mention both 2.2V and 3.3V), the problem here is that 2.2V is lower than the requirement of >0.7*VDD to be interpret as a logic high input. So I do not recommend that you connect the two reset pins together no. One problem you can see is escessive current into the input buffer of the nRF52832 if you do this (the input can tristate). In addition the internal 13kohm pull up on the nRF52832 reset pin will feed the reset pin of the nRF9160, which will cause the ESD diode on this pin to continously sink current, which is not good either in the long run. Is there no way you can run both IC's on 2.2V? If not, I would suggest you look into switces that possible can connect/short two pins to ground instead of one.

Kenneth