physical connections between the GSM module and the arduino

Hey everyone, After two days of trying(in vain) to send/receive/make a call from my SIM300 module to the arduino,and reading up various blogs online,i'm left very confused on what i actually need ,to make the connections. Here are the things i'm using/doing:

1)12v ,1A DC adapter to power the SIM300 module

2)using the software serial library on the IDE and connecting pins 10 and 11(on the arduino) to tx and rx(on SIM300) respectively.

3)connecting the grounds of the arduino and the gsm module.

I read on a couple of blogs, the need for a ttl converter while using the SIM300.Why do we need it,if the max232 chip is already on the board and it can reduce the RS232 volatage level to TTL?? and the hyperterminal??Is that essential,for me to be able to send and receive an SMS??

I'm pretty much a beginner ,having dabbled in fairly basic projects before this and never one with a GSM module, so any help will be appreciated! :-)


Also,my code(in case something is glaringly wrong in it) :expressionless:

#include <SoftwareSerial.h>
SoftwareSerial mySerial(10,11);
void setup()
mySerial.begin(9600); // the GPRS baud rate
void loop()
mySerial.println(“AT+CMGF=1”); // set the SMS mode to text
mySerial.write(34); //ASCII of “
mySerial.println(“hello”); //this is the message to be sent
mySerial.write(10);//Ascii code of ctrl+z to send the message

Like posting here is useless unless you get some feedback, sending commands to the phone module is useless unless you check for a response. Perhaps your phone is telling you what is wrong, but you are not listening to it.

Hello PaulS, Thanks for absolutely nothing. Very instructive feedback! Also,very encouraging for a beginner to continue on!Thanks for the help .

What's your problem? I suggested that maybe your phone is trying to tell you what is wrong. If you don't like that idea, or don't care, then enjoy having a non-working project.

@trapiz_proj You should check out this library I wrote: :)

Hey,Lauszus, I'm working on SIM300,Could you in brief, tell me the physical connections while sending out an sms using Softwareserial?? Very new to this and i connected the rx and tx pins(0 and 1) to the GSM module's tx and rx and connected the grounds together.Is that incorrect?

@project_quest When using my library the RX and TX for the software serial communication is by default located on pin 2 and 3 respectively. You will need to connect RX (pin 2) to TX on the GSM module and TX (pin 3) to RX on the GSM module. You would need to connect GND as well as you said.

Also you will need connect the powerpin (pin 4 by default) to the status pin on the GSM module - this allows the Arduino to turn the GSM module on and off.

The pins can be set in the constructor like so:, so you can change them if they are already in use.

Hopes this answers your question.

Regards Lauszus