Help with Elecrow SIM808

Hello All,

I’m doing a project on a GPS vehicle tracking device. I just got a SIM808

I’ve been using the code at and I have this problem. All I get is AT AT AT AT.

I don’t know what do to do now.

Best thing to do is this basic test to see if you can communicate with the Sim Shield.

First though, check the Serial Jumpers that they are selecting D7 and D8.

/*  Basic AT tester for Sim900/800 Shield or Module Without a Sim Card
 *  The sim900 shield or module can be run from the Unos power supply.
 *  Power On the Shield, the Net led should flash 1hz and the Status led  is on. 
 *  Upload this program, start the Serial Monitor at 19200 baud
 *  Type AT  in the top box next to Send and then hit Send or Return.
 *  It will return OK is its got through to the SIM chip.
 *  Type in  AT+GSN and it should return the IMEI number printed on the chip

#include <SoftwareSerial.h>

SoftwareSerial SIM900(7,8);    // RX, TX

void setup()

void loop()
  if (SIM900.available())
  if (Serial.available())

It repeats whatever I type in. I don't see any OK

You need to check these jumper settings, as pointed to in my picture below.

Look on the actual shield, one side should have D7 and D8 printed on them, thats the position for the jumpers.

( do not rely on my or the pictures on the web sites being the same as your board, they can make changes)

What Arduino board are you using ?


Excuse me but I'm very new to this.

Do I have to set the jumper in hardware serial mode for this to work? How exactly do I set the jumpers. The guides I've seen are not very clear to me. What connects to what?

You need to look at your board.

My picture in the last entry points to those jumpers.

On the actual green circuit board by those jumpers you will see some markings, on each side they will show some numbers like D0 and D1 or D7 and D8

One side is nearest the Sim chip, the other towards the board edge.

What do they say ?

On the jumpers, I see GPRS_RX and GPRS_TX. There are no numbers or markings here.

But my board looks like this |500x328



Ok, then the jumpers should be in the position shown in the picture above, that should select D7 and D8 for the connection.

Importantly - you have not said what Ardunio board you are using, Uno ,Mega etc ?

Reason it will not work with some boards without modification.

What happens when you press and hold the Power key for 1 second then release.

Does the power led come on. ?

Does the NET and STATUS leds come on ?

Have you used a separate power supply for the Sim shield ?

Yes, I moved the jumpers to hardware serial. All the lights come on.

Now, my project is based on so I think it has to be on HWSERIAL. Is that right?

Its always difficult to establish what happening with other folks hardware without seeing it first hand.

The project to are looking to follow should be disregarded for now as you need to prove the board works at all.

For such basic AT tests its normally used with the jumpers in the SW Serial mode which Normally select D7 and D8 pins.

So you should use that , BUT you still have not said what Arduino Board you are using ????

If its a Mega 2560 then that will not work .

Sorry, I'm quite confused myself. I'm using an Arduino Uno

What I'm doing is based on and I'm using Elecrow SIM808.

In software serial mode, all I get is AT AT AT AT.

In Hardware serial mode, all the commands echo back and then gets stuck on CGPSStatus.

I want to be able to modify the code to work with my gsm shield and later add a functionality to control a relay switch using sms.

I've been able to make calls, send sms, receive sms, get GPS coordinates using the SIM900 library. But I'm a noob and I'll I want to do is to do the same project done in the link above.

deekson: I've been able to make calls, send sms, receive sms, get GPS coordinates using the SIM900 library. But I'm a noob and I'll I want to do is to do the same project done in the link above.

Ah, afraid I misunderstood your first post, thought you meant that you could not get the Sim shield to work at all.

Clearly is just a problem with that sites code as you now say the board works fine with other sim900 code.

Have you tried contacting that sites author for help with his code ?