Sim900 Arduino shield

[nerdmedic]

I have a Sim900 Arduino shield but even with a known good SIM, I am not able to get it working and it doesn't appear to initialize. Do anyone know of a good Arduino sketch that could be installed to help me troubleshoot and figure out why it will not connect to the GSM network? Or perhaps a good reference for the AT command set for the SIM900?

[William]

Hi,
The manual didn't help?
http://www.geeetech.com/Documents/SIM90 ... _V1.03.pdf

[nerdmedic]

No, unfortunately, the AT Command Manual didn't help because I cannot get to the point that I can query the module using the AT command set. I have tried both SoftSerial (on ports 8 and 7) and hard serial on 1 and 2 and I have not been able to communicate with the module. The only return I get is an error code that the module is not ready... which would make sense if I don't have the communications pins right.

What would probably be most helpful would be a schematic of the shield so I can see how the serial pins to/from the module are routed. At this point, the only clues I have are from the screenprinting on the board and they have not been shown to be accurate at this point.

Nerdmedic

[William]

I'm not sure which one you've bought of the two shields:

QQ截图20161022134356.jpg (92.47 KiB) Viewed 6573 times

And don't know if it helps:
http://www.geeetech.com/Documents/GPRSshield_sch.pdf

[nerdmedic]

In the picture provided, the one I have is on the right.

[William]

OK,the schematic i posted belongs to the right one.