I want to send some data through SIM900A GSM, and stumbled upon this:
AT+CIPSTATUS
CONNECT Ok
AT+CIPSEND
+CME Error: 3 (operation not allowed)
This just happened once, otherwise following the same procedure I have been able to send data succesfully. I can see that I did not receive '>' prompt What could be the problem?
If it only happened once, and you can send data normally, then it was probably some software problem in the device firmware, that it wasn't in the correct state for some reason.
There could be many reasons for this, for example: Connection Profile not set correctly or network temporarily unavailable.
You could implement some code to disconnect, wait and re-try if this happens, and hope that it doesn't happen too often.
When you are sending data through a modem, you are dealing with
- your software
- the device driver
- the device firmware
- various different components of the mobile network
If any of them apart from your software send the wrong response, you'll get an error like that.