I use a GM862 – GPS set to auto answer when an incomming call happens.
Most of the time the modem pick-up the line and immediately hangs up.
Can someone advices me what could generate this issue ?
Many thanks for your help,
Maybe you have set AT&D to 2 and you don’t manage the DTR line. See Also AT+CVHU.
I do not see well what AT+CVHU does exactly.
Can you explain me please ?
Actually i indeed do not use DTR line , it is tied to ground on my project.
What AT&D setting should i set then in order the modem does not disconnect just after picking it the call ?
AT+CVHU does for voice calls what AT&D does for data.
AT&D0 and AT+CHVU=2 should ignore DTR, if is not tied somewhere and swings freely.
I also notice that sometimes when i push the button to power-on the
modem, the STAT led flash during network search and after few seconds
the modem switch it off by itself.
You should check your power source and related circuitry then, solve this issue then see if the hang up still occurs.
I’ve added a 2200uF cap near GM862 module, now power supply is stable.
However the modem still hangs-up the line by itself when an incomming call comes-up.
Do you really think this problem is due to DTR line that is grounded on my board ?
i cannot un-ground and leave it in theair for test because this pin is not accessible on the pcb ( the ground wire runs under the molex connector )
If you are sure DTR must be left unconnected, then i will redesign a PCB again, but first i need to sure problem comes from DTR line.
Thanks for your support.
It is ok to have DTR grounded, it isn’t a problem at all.
Do you have the same issue also for outgoing call?
All incoming calls are dropped?
After a dropped call, is the GM862 still on and able to receive AT commands?
Fw version of the module used?
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