URGENT - no response from the module

Hi all, i had a wavecom module q2501b working for soveral days, connnected to a server and transmiting its position(gps). One day, i simply had no responce from the module. When i connected a serial cable to it, there was no reply to AT commands(no echo either). After disconnecting the module and connecting it again, my firmware started to run ok. I´m afraid it will happen again, it looked like the OpenAt firmware wasn’t working. Did anyone experience the same problem? is there any way of fixing it without using an external watch-dog circuit?

thaks, Sérigo

Hi Sérigo,

I doubt that this is a problem with the Wavecom core firmware…

When the modem didn’t respond, it probably was turned off… Does it run on batteries? It will itself turn off when you drop below a certain battery voltage… Also, are you using GSM/GPRS communication? Then you might have high peak currents (pulses) that may cause the modem to shut down if the battery / power source can’t supply the required current.

When you say “my firmware” you refer to an embedded application that you programmed, right? Is it possible that there is a bug in your software?
( Unfortunately, I experienced writing bugs myself :unamused: )

Best Regards,

Thanks for the reply. I´m using a battery power supply, but i´m shure thre is enough current o support a GSM/GPRS communication. There may be a bug in my firmware, but if my code caused any exception, the module still should be responding to AT commands, am i right? And, as far i know, there is a watchdog timer that should reset the module in case of any exeption. I wonder if some oscillation on the voltage could couse the module to shut down itself.

hello sergio,

Are you using a starter kit or an own board?


I´m using my own board.

Please check the voltage level of the interfaces. That could cause that kind of hang-up. Of course, we run into it. :slight_smile:

But now we are wondering how could VCC_RTC on q2406 output 15 mA when
in the docs there is max 2 mA stated.

Best Regards,


I have got a similar problem:
AT Commands are not replied.
The GSM status LED ist either on or off, but not blinking.
Voltage supply is ok.
Out Application seems to be stopped.

Can you tell me, what can be the reason for behaviour like described?


I advise you to put an external watchdog circuit, it could solve the problem.
Stability in power supply is essencial.
best regards,