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Sim900 module - sim card top up alert

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Wp100

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Have got a Sim900 module working well sending out a sms alert message ; its using a Tesco(uk) pay as you go sim card and controlled by an Arduino.

Its just got one little problem that I was hoping could be overcome, but after looking at the Sim900 AT command set I''m not sure it can.
At the moment, when sending out the alert I am also sending the number of messages sent since the last top up.

What would be better would be if I could use the AT commands to read a register that indicates the prepaid value is now low ; the provider puts out a verbal message to this effect, but wondered if that in any way changed any AT registers ?
 
As far as I can tell, you can find the Tesco mobile balance by dialling *#10#. If so, you can do the same thing through AT commands like this:-

AT+CUSD=1,"*#1345#"

OK

+CUSD: 2,"Your ASDA Mobile credit is now #0.25. If you have purchased a bundle, please call 2732 for further information.",250


This example is from a few years ago, and I think that ASDA are now using a different network so that codes don't work, but you should be OK with Tesco as long as the *#10# code works.

The first line is the command that you need to send. You will need to change the code to *#10#.
The mobile device will reply with "OK" almost immediately.
The last line appears maybe 5 - 10 seconds later, when the network has responded to the request for credit. You will have to see what form that is to work out how to find the credit from it.
 
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