Hi I'm going use the terminal armbian and send AT commands to the gsm SIM800L, but I am uable to write these commands. I used screen and minicom like this : screen /dev/ttyS0 115200 & minicom -b 115200 -o -D /dev/ttyAMA0 I use to connect to ttyS3 but nothing happen i think the uart3 or pins 8 and 10 is not working or not enable of course i have ttyS3 in ls /dev list but not working. I've connected according to the following guidelines:
i use : orange pi plus 2 board armbian for orange pi plus 2 SIM800L v2.0
image of my connection and board :