Sim900 GSM module

Good day everyone, I got a sim900 GSM module and connected it to my Arduino uno board using the instructions from http://www.geeetech.com/wiki/index.php/Arduino_GPRS_Shield but whenever there’s a sim in the module, the status and netlight come on for a while before they go off and don’t come on again, when there’s no sim, the status light stays on and the netlight blinks fast. I have uploaded various codes and have not got any output or return via the serial monitor, its like it doesn’t even recognize that there’s a GSM shield there. All the AT commands I have sent have returned nothing whether there’s a sim in it or not, please help, I need the assistance urgently. I have attached some images of my set up

Hi,

Couple of things to check first.

Any reason you have not plugged the shield onto the Uno ?

Cannot see from your pic how the shield is set up, two things to check.

From the pictures below, when powering the shield from the Arduino the switch indicated by the red arrow should be in the position shown, for an external 5V supply you move the switch to the other position.

(Think your board will be ok if you have fed it with 9v )

Next check the jumpers, red circled , first their position and also that your board has the legends D7 and D8 printed.
( have seen some boards use different pins )

If using jumper wires then yes D7 to D7 and D8 to D8.

000158.jpg

000157.jpg

With the code I sent you, this is what you should see using the basic AT commands to talk to the Sim900 chip, without any Sim card and powered from the Arduino board.

The most basic test is just ’ AT ’ and you should get back OK.

You are keying in the AT commands to the single line box next to the SEND, rather than the main screen which is for the data received from the Sim900 ?

I don't have this exact shield, but on a similar one I was initially fooled by the fact that you have to turn it on. You can do that by holding down the hardware button on the board or by using a digital output pin on the board as per the instructions on the wiki.

Another thing I had to do on my shield was to change the baud rate - the default one for the board was too fast for software serial on the Arduino.

Hopefully it is that simple.

Hey, thanks for the reply, when I stacked the GSM on the Arduino, and ran the code, I got "error opening serial port 'COM 32', and when I tried to open the serial monitor, it says "board at COM32 is not available" my Arduino is connected on that port so I don't understand, when I did not stack it, I was able to open the serial monitor, tho it was blank, it returned no value, the baud rate was 19200, it was like the GSM wasn't available or wasn't communicating with the Arduino. I have attached some images, please help

Hey, thanks for the reply, when I stacked the GSM on the Arduino, and ran the code, I got "error opening serial port ‘COM 32’, and when I tried to open the serial monitor, it says “board at COM32 is not available” my Arduino is connected on that port so I don’t understand, when I did not stack it, I was able to open the serial monitor, tho it was blank, it returned no value, the baud rate was 19200, it was like the GSM wasn’t available or wasn’t communicating with the Arduino. I have attached some images, please help

when I stacked the GSM on the Arduino, and ran the code, I got "error opening serial port 'COM 32'

This sounds like an error from the IDE and not from "running" the code.

From the documentation you linked to, it looks like the board can be configured to use hardware UART for serial communications. If you are using an Uno, there is only one hardware serial port and it is also used for communications with the IDE and any communications with the serial monitor.

Try changing the jumper to use software serial on pins D7 and D8 and include the SoftwareSerial library and use that.

Alternately, you can move up to a Mega which has three additional hardware serial ports. They won't work with your shield as is, so you will have to use some jumper wires from the jumper pins to the hardware serial ports.

Are you actually trying to drive the SIM900 from Arduino code or are you using the Arduino as a pass through from the serial monitor to the SIM900? Can you post your code as I'm not sure I fully understand what you're trying to do and from where.

That code works fine on my Uno /Sim900.

You have not answered the previous question about the printed text is besides these jumpers -what does it say ?

jumper.jpg

@ricky101, the words next to the jumpers are D1(RX) and D0(TX),
@davidrh, when I put a sim in the module, it tries to register on the network and then it powers down…only the power light is on, status and netlight power off. so j decided to test it without the sim using AT commands and I connected the GSM to the Arduino and ran the code which @ricky101 sent earlier so I could get the IMEI of the sim900, but it also returned nothing on the serial monitor, I dunno if it may be a firmware issue, but I can’t even check the current firmware version because all AT commands I have been sending, none has returned anything on the serial monitor.

aycoolt: @ricky101, the words next to the jumpers are D1(RX) and D0(TX),

So theres your problem, you have selcted pin D0 and D1 for the comms to the PC.

Your software is specifed as D7 and D8

The PC /Serial monitor use D0 and D1 , so theres the clash.

As said earlier most shields with the jumpers as you have them are coded for D7 and D8

Looks like you have the type thats not .

What to the legends say on the other side of those jumper pins. Can you prodive the exact link to the board you bought.

but @ricky101, at the other side of the jumpers are D8(Rx) and D7(Tx), I bought the board on Aliexpress, how do I select D7 and D8, if I've previously selected D0 and D1, and is there no way firmware is related?

As the picture of your jumpers in post #7, just pull up and off the 2 little black jumpers and then replace them so they are across the other pins.

Then run the code again and it should work

The pics below shows how to jumper them.

000166.jpg

Wow..@ricky101..thanks a million..gracias..Merci beaucoup..Asante sana..that was the solution, I've been using D0 and D1 all this while..thanks boss..very very grateful.. Its responding to AT commands now, I will now put a sim in it and try it out.

Now with a sim in it, the status comes on and the netlight blinks but they both go off after like 5 seconds, could it be power issues?.. I used a 9v battery to power it

Phew !!! :D :D

You might this tutorial good, though the site its on is not the originator.

http://milesgraham.co.uk/index.php/2-uncategorised/30-tutorial-arduino-and-sim900-gsm-modules-part-2

aycoolt: Now with a sim in it, the status comes on and the netlight blinks but they both go off after like 5 seconds, could it be power issues?.. I used a 9v battery to power it

It should work, for testing with the Sim card from the Unos 5v supply.

The sim900 shield specifies a 5V input to the jack socket.

Have tested my board with 9v on the jack socket and the boards regulator remains good at 4.2v , so hopefully you should not have damaged yours, but do not use 9v long term.

Why the shield is powering off after 5 seconds when the sim card is in, do not know ?

Have you inserted it correctly, you open the top part, slide the sim into the top part , then close it down on to the bottom part and slide it forwards to lock it.

Are you using a full size sim card or a micro one in a holder ?

Have you tried another 2G sim card ?

Have found another post giving the same 5 second problem. https://forum.arduino.cc/index.php?topic=383424.0

When you run from the Ardunio without a Sim it works ok.

When you put a Sim card in it goes off after 5 seconds.

When you powered it with 9v it did the same - yes ?

When you powered it with 9v , did you switch the Power slider switch over to External ?

Thats the black switch next to the jack socket - for Arduino power its pushed down towards the middle of the board. For power from the Jack socket it must be switched up towards the board edge.

Are you doing that ?

I have fixed the sim in the right position, its a full mini sim, the GSM has some IC that I just read about that serves as volatage regulator and has 3A output, so I don't think its power..I've also tried another sim..same response.. could it be an antenna problem?

You have not answered my question about the power slider switch .

Are you changing it over when powering it from the jack socket ?

This is how it should be when powering from the Power Jack.

You said it was a 9v power supply, but no mention of what its current rating was ?? if its too low then it may also give the Sim problem …

000167.jpg

aycoolt: I have fixed the sim in the right position, its a full mini sim, the GSM has some IC that I just read about that serves as volatage regulator and has 3A output, so I don't think its power..I've also tried another sim..same response.. could it be an antenna problem?

Whilst the regulator can output 3a, it still has to source it from somewhere. I doubt a pp3 battery will supply the peak current you may need....