Can you give me any sample code to send at commands to outside module and receive return value?

[Yusuke]

I'm new to nRF9160. I have some experience of implementing stm32 MCU and HL8548(3G module). 

I want to send at commands to outside module like Wifi module, and receive return value from it.

[Hakon]

What do you mean by outside module? Is the wifi module on the same PCB as the nrf9160?

[awneil]

Yusuke said:

I want to send at commands to outside module like Wifi module, and receive return value from it.

That's just a matter of sending bytes out of the UART, and receiving bytes into the UART.

Above that it is entirely generic and independent of the underlying hardware.

To work out what commands to send, experiment by using a terminal to type the commands manually, and observe the responses.

The key thing to remember with AT commands is to make sure that you pay attention to the response from each command; do not send a new command before you have received and handled the terminal (ie, final) response to the previous one.

Do not rely upon blind delays!

https://www.avrfreaks.net/comment/2209136#comment-2209136

EDIT

See also: https://www.avrfreaks.net/comment/2306021#comment-2306021 - and follow links for some AT Command libraries...