I have a problem with data calls where i am unable to hangup one of the modems if the other looses GSM connection while the data call is in progress.
Let’s call the calling modem ‘A’ and the receiving modem ‘B’. I have tried the following conditions:
V.110 protocol and old type with long handshake.
The problem occurs both with OpenAT software enabled and without.
Modem A makes a data call to modem B. They both write CONNECT 9600 and are connected. Suddenly modem A or B looses its GSM connection (due to very bad signal strength) and writes NO CARRIER. However the other modem does not know that the connection has broken down. If i write ‘+++’ on the modem that still thinks it’s connected, then i can write ATH but nothing happens. The modem still flashes the FLASH LED fast to indicate a running data call. Hyperterminal does not answer with OK after the ATH. So i am not able to stop the call anymore. No other AT commands gives any response. The only command that works is AT+CFUN=1 which then restores the modem.
How do i get the modem to hangup the connection when this happens?