I\'m a beginner in stackoverflow so I cant add a comment.
I saw this page:
Read command output inside su process
and I tried this answer and it is ok:
First I think you are just sending the AT command to stdout in the shell which will not do anything other than giving you an echo which you read back. For this approach to work you have to redirect the echo command to the serial port device file. Android phones use various devices for this, /dev/ttyGS0
and /dev/smd0
seems to be common names.
However I would suggest using the program atinput to send AT commands and capture modem responses. It is specifically written to be used from the command line like that. That will relieve you from communicating directly with the modem and the only thing left is the pipe handling reading the response.