nRF9160 DK UART Connection with External MCU

[Hamza_HK]

Hi, 

we have a nRF9160 DK where we have uploaded the AT_CLIENT example on. Have tested the board and it works fine, able to send AT Commands and join to the network etc...
Now we want to communicate with the nrf9160 modem through UART with an external MCU.

How can we connect the external MCU with the nrf9160 board through UART?

We have looked through the forum and the user manual but we were not successful with achieving our goal. We have also tried this example to establish serial communication with the nrf9160. 

The external MCU is a nrf52840. 

Would appreciate any help! 


Best Regards,
Hamza

[Hamza_HK]

Hi,

Update: 

We managed to make it work with Serial LTE Modem example. Following this guide and scroll down to connecting with an external MCU. The only issue this doesn't work is that the guide does not state how to get GPIO output level on nRF9160 side to 3V. @Heidi states on this forum discussion that the SW11 is to be set to 3V for to get the correct GPIO output level. So the solution is as follows: 

on nRF52840 DK we flashed nrf52 client lte

on nRF96160 DK we flashed serial_lte_modem 
on nRF9160 DK set SW11 to 3V (!!!!)

Connect UART pins according to connecting with an external mcu table in slm description

If those steps are followed correctly, then nRF9160 UART is accessible and responsive to AT Commands.

Hopefully this is helpful for everyone! 

Regards,
Hamza

[Sigurd]

Hi,

Great!

Hamza_HK said:

The only issue this doesn't work is that the guide does not state how to get GPIO output level on nRF9160 side to 3V

 Thanks for the feedback. I agree that the guide should include this information. I will forward this improvement suggestion to the team.