GPRS Signal Strength on GPRS Datacard

[Tim Bartle]

Hi All,

Sorry for the cross post, but it seems to fall into all of the 3 categories.

We are using an Option Globetrotter GPRS Datacard (The red one that Vodafone
sell in the UK).

We can successfully make a GPRS connection by manually creating a DUN
connection and then calling it with RasDial(). Unfortunately we are unable
to send AT commands directly to the card because the create file for what we
believe is the correct COM port (4) always returns -1.

We have a requirement to read the current signal strength from the card in
order to determine whether there is sufficient signal to reliably complete
our communication.

Does anybody know either:
a) how to open the COM port
b) An alternative mechanism for finding the signal strength

The development environment is C# in Visual Studio .NET 2003 (Although we
would be almost as happy with an EVC++4 solution if we could just get it to
work ....)
The device is a HP Ipaq 5550 with Windows Mobile 2003 and .NET CF SP2

Tim Bartle
Lead Developer (Client)
Atos Origin

 

[Adam Goetz]

While I cannot answer your actual questions, one gotcha to watch for, is the
modem class B or C? If the modem is class C then you cannot access any GSM
function (which includes the AT commands to get signal strenth) while the
modem is being used for GPRS functions. If this case, you must query the
signal strength, release the port, then establish the gprs connection.

 

[Tim Bartle]

Thanks for this Adam, we already have the code working fully on the Win 32
platform, so I presume the modem must be class B.