Galaxy s3 + does not respond to AT commands sent from the Arduino USB

Projects Networking, Protocols, and Devices
1

Hello everyone, I have the problem described in the topic after a series of tests, in particular:

  1. I connected the two with cable Arduino serial cable to the USB OTG then inserted into the cell
  2. I created a sketch that sends USB string AT + CR + LF and waits to read characters coming from cell
  3. On the Arduino TX LED flashes then the characters are actually shipped on USB
  4. Not getting anything from cell to cell I used the 'app' Android USB serial monitor lite "to see what comes from Ardino: get the string AT + CR + LF. With the 'app I send a string and it is recognized by the LED Rx Arduino and my sketch.
  5. .... I did other tests between PC terminal emulator and cell and saw that the cell responds to AT +

Does anyone have any advice to solve the problem or tell me where to go to document ??????

Thanks in advance for answers

sp_ma_54