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I have Sim900 built on Fez Domino


i have sim900 and on initial connect works very well, but when something wrong happens for example if sim card removed or antenna is out of coverage area the device stops functioning. I want to know how to establish connection(reconnect) again? using AT commands. what is best way to do this?


I assume you are using the GPRS modem.
Some modems accept an escape sequence to get back to AT command mode. For example, you send “+++” to the modem to go back to AT command mode. You need to check that the modem’s manual.
The other way is to connect the modem’s reset pin to one of the GPIOs and you simply reset it using FEZ


Maybe you can connect the data carrier detect to a interrupt pin. The DCD will change when you get dropped of the network. On that event you can send ATH or +++ and reconnect.

A connection is established with ATD