SIM900 Sainsmart not responding


first post in here.

I've just bought this module

it doesn't seem to work. I connected it to arduino e tried a code, but doesn't work. problem with communication. so i have some questions:

  • may swapping tx and rx pins be cause of damages?
  • module responds to incoming calls (ring led)
  • sync led blinks slowly (that's seems ok)
  • when i upload the code, monitor starts searching for best baud rate, but it cannot find it, and after minutes and attempts at different BaudRates it says "module not responding", "system IDLE" (or something like that).

later i'm going to post code and error message

can anybody drops some hints? tnx

bye Valerio

(PS sorry for english mistakes, i'm not mother tongue, i studied for first certificate but never applied for it, and I got rusty :smiley: )

Some basic problems encountered when using GSM/GPRS devices.

No, swapping Tx / Rx pins shouldn't affect it.

I checked basic problems
-power it's ok. I use 12v switching 5A P.S., it goes directly to arduino, also send 12v to step-down converter 5V 3A, that goes to GSM module.
-I connected TXD (module) to pin 0 RX (arduino), and RXD to pin 1 TX
-sync led is blinking every 3 sec.
-i don't know which library have to use , this may be the problem,

there are jumpers, that I don't know how to set, how it's possible that a module hasn't got its own instructions?


There's a link to documentation on the page you linked to. Nothing useful in there?

I have one of these somewhere, unused. I'll see if I can find it over the weekend.

of course i’ve red your info at the link… i tried to run the code you suggest

Check that it works

The first job is to ensure that we can communicate with the shield.

//Serial Relay - Arduino will patch a 
//serial link between the computer and the GPRS Shield
//at 19200 bps 8-N-1
//Computer is connected to Hardware UART
//GPRS Shield is connected to the Software UART 

#include <SoftwareSerial.h>

SoftwareSerial GPRS(7, 8);


nothing doing , system crashed, I had to reset.
tnx anyway :slight_smile:

The page YOU linked to: - there is a download link at the bottom. This includes a schematic. Unfortunately not for this device! I think it actually covers several devices, a pick 'n' mix.

i red them all... useless.