Operation
Before the GM29 can be operated the following conditions must apply:
•SIM card inserted (with the modem unpowered);
•antenna connected;
•RS232 port connected to the application computer;
•power applied.
Operation is not dependent on a handset being fitted. The type of application will dictate whether a handset is necessary.
Switching On the Modem
There are two ways to switch on the modem, once power is applied.
•either assert TO_IN high for > 0.2 s;
•or activate the RS232 control line DTR, high for > 0.2 s.
The modem is fully operational after 4 seconds. Logging onto a network may take longer than this and is outside the control of the modem.
The modem can be configured to start up at the time power is applied by permanently tying power connector signals TO_IN (pin 4) and VCC (pin 1) together. In this case DTR must be used to switch the modem on again after it has been switched off or reset, while power is still applied.
Switching Off the Modem
There are two ways to switch off the modem as described below:
•either use the appropriate AT command;
•or assert HR_IN high for 1 - 2 seconds. A delay of up to 10 s is experienced as the modem logs off the network.
Resetting the Modem
A full system reset, independent of the status of the software, may be applied to the modem as follows:
•assert HR_IN high for > 3.5 s.
Operating States/LED
The GM29 has a green LED, as shown below, used to indicate various operating states. These states are described in the following table.
LED |
|
Operating state | LED |
After switching on the modem | On after 4 s |
|
|
Switch off or power removed | Off |
|
|
Standby or talk | Flashing |
|
|
Modem on with one of the fol- | On |
lowing conditions: |
|
No network, network search, |
|
no SIM card, no PIN entered |
|
|
|
10 Operation