Arduino UNO and GPRS

The isssue: GPRS does not communicate with the arduino uno board.

Some have suggested updating the SIM900 firmware. Can anyone confirm
that updating this will fix the issue?
This is very frustrating.

An acknowledgement or discussion of what exactly what is happening
should be done.
I cannot believe that you guys would ship this product with such a bug.


I am having the exact same issue as you. Did you manage to install the firmware update and if so, did it fix your problem?


I have not done the firmware update yet, but I should be soon.

If you could post or PM me after you do I would greatly appreciate it. I will be troubleshooting this device all week and will be sure to post if I find a way to make it work.



I have the same units and mine worked fine without updating any firmware.

Things to check

Your jumpers are in correct position. This depends on what you are doing are you sending serial info through a terminal or are you trying to do it through code?

When you turn the gsm unit on does D2 stay red? does D1 blink green every 3 seconds or is it blinking every second?

Which Arduino version are you using 1.0 or earlier? This matters as most of the example code on the wiki is relevant to earlier versions to 1.0

Have you mounted the board correctly the pin closest to the aerial output should go into RX the rest will then line up so digital pins 0 through to AREF should be connected and on the analog side reset through to A5 should be connected.

Let me know once you check all of these and i will try and help a bit more if I can

Thanks for the tips…

I am using the arduino in pass through mode.
The GPRS turns on and shows the very initial
stuff like 255 255 255
but then does not say anymore.
This seems to be a common issue.

I think either your GPRS is newer or you have a newer firmware
on it.

I will post more when I get a chance to solve this…

what about the LEDs does it blink every 3 seconds?

Are you using Mac or Windows?

What serial monitor are you using ? I found arduino serial monitor to be unreliable so try a different one if you aren’t already.

What code are you using on the Arduino can you post it?

Has anyone gotten this to work on arduino?
I’m using softwareserial 19200 baud rate
in the arduino code I send the commands from the software tx rx to arduino harware tx rx
then I use a terminal program to connect to the arduino/sim900 stack
Sometimes I get bad communication, sometimes none.
Instead of proper boot i get something like yyyyyyyyy