NRF9160 SLM connected to NRF52840, Inverted UART logic

RE: NRF9160 SLM connected to NRF52840, Inverted UART logic

LarsV — Thu, 17 Feb 2022 13:37:58 GMT

I solved the problem myself. The IO voltages on the two development kits were different. One was on 1.8v and the other on 3.3v. 3.3v on 1.8v logic is a "high". While 1.8v on 3.3v will give sketchy results at best, and no results at worst.

RE: NRF9160 SLM connected to NRF52840, Inverted UART logic

LarsV — Mon, 14 Feb 2022 14:33:27 GMT

Hello,

Yes, I've followed the connection guide, and have connected the pins as said in that guide. I'm running SDK version 1.8.0.

RE: NRF9160 SLM connected to NRF52840, Inverted UART logic

Øyvind — Mon, 14 Feb 2022 14:03:55 GMT

Hello LarsV,

Can you please elaborate on how you have connected the nRF52840DK to the nRF9160DK? Have you followed the Serial LTE Modem documentation on Connecting to external MCU? What version of nRF Connect SDK are you running?

Kind regards,
Øyvind

RE: NRF9160 SLM connected to NRF52840, Inverted UART logic

LarsV — Sun, 13 Feb 2022 14:18:16 GMT

Yes, i did verify that the connections are correct

RE: NRF9160 SLM connected to NRF52840, Inverted UART logic

ivnn — Fri, 11 Feb 2022 23:33:48 GMT

Did you try to swap Rx Tx lines?