GSM Modem not working...!!!

[nikhildascl]

I am doing a project using GSM Modem with AT89C51. It was working fine for the last 2 weeks. But now, it is not working. Actually, not showing any network signal. Please help me to solve this.

 

[ckshivaram]

check the modem individually with hyperterminal and see if it is responding to AT commands, then connect to your controller board.

 

[nikhildascl]

I cannot connect the modem with hyperterminal. There is a problem too. I dont where the problem is. When I connect the modem to the hyperterminal, there is no communication between then.

 

[ckshivaram]

did you check the serial cable connectivity? using multimeter check the continuitr between pin to pin. especially 2,3,5 pins. what is the power supply adaptor you are using for the modem. Is the modem powering on properly.

use one to one cable with pin 2 connected to 2, 3 to 3 and 5 to 5. this is straight cable. if not connect 2 to 3 and piin 3 to 2 and pin 5 to 5 in the cable and test the modem and let me know.