Data Application

What's the maximum timeout value when using the AT + CIICR / AT + SAPBR command to start the wireless connection with SIM900 modules ?

90S
What's the maximum timeout value when using the AT + CIICR / AT + SAPBR command to start the wireless connection with SIM800 modules ?

85S
In what circumstances will SIM900 automatically report "CLOSED" after establishing the TCP connection ?

1) The connection of the TCP server is closed ( if the module acts as the client ).

2) The module cannot receive the confirmation from the far-end after the maximum timeout.

3) The network is disconnected due to abnormal conditions.
How do I deal with the problem when the modules are unable to connect to the GPRS service or the data transmission is blocked ?

If it is because the GPRS service is not appropriate to a particular cell, users can use AT + CENG to query the available cells nearby, and connect to another unit through AT + CELLLOCK.

If it is because the cellular capacity is full, users can set the module to low level GPRS through AT + CGSMCLASS. In this circumstance, the module can work normally despite a low speed.
Do SIM800/SIM900 modules support the Nagel algorithm ?

Yes.

Users can enable or disable the Nagel algorithm through the AT + CIPOPTION command.

For the SIM900 series, it is enabled in SW in default. For the SIM800 series, it is disabled by default.

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