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Topic: Sim900 crashing (Read 518 times) previous topic - next topic


I have a sensor which is uploading information to a server using a sim900 from

using this library https://github.com/MarcoMartines/GSM-GPRS-GPS-Shield/tree/GSMSHIELD/doc

I'm having problems though because after a number of hours it seems to stop sending to the server, I know that the uno is still running and the sensor is being used but the GSM shield is unable to upload the information.

Any ideas why this might be and is there a way to reset the sim900 in the code or to detect if it has crashed?



Any ideas why this might be

Hardware might be having problems.
Software might be having problems.

and is there a way to reset the sim900 in the code


or to detect if it has crashed?

Of course. Send it an AT command. Read the response. If there is no response in a reasonable time, use it to send you a text message.
The art of getting good answers lies in asking good questions.


Most probably you have lost command sync with the 900

By which I mean you must wait for reply from 900 and never send another AT command before the previous command responce has been see.

I have tested many of the GSM modules most initially fail to respond in this situation but eventually some firmware timeout resets and the module comes back, my notes on the 900 imply this as with the Seimans tc 35i the only way out of this situation  is to physically reset the module.

8) 8)  Happy Coding..


I've just had a quick look at the schematics and it looks like you can use software to turn the shield on and off. If this is the case then periodically send an AT to the shield and if it doesn't respond within a certain time turn the shield off and back on again.
Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

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