Problem with gsm module simcom SIM900 ??

How to interface gsm module- simcom SIM900 with Arduino Mega2560? and

In the reference, I saw that.....

The Arduino Mega has three additional serial ports: Serial1 on pins 19 (RX) and 18 (TX), Serial2 on pins 17 (RX) and 16 (TX), Serial3 on pins 15 (RX) and 14 (TX). [u]To use these pins to communicate with your personal computer, you will need an additional USB-to-serial adaptor, as they are not connected to the Mega's USB-to-serial adaptor[/u]. To use them to communicate with an external TTL serial device, connect the TX pin to your device's RX pin, the RX to your device's TX pin, and the ground of your Mega to your device's ground.

I didn't get the underlined statement... someone please elaborate it to me.

Any help is appreciated.

Could you post a link to the SIM900 device you are trying to use?

Very much similar to this... you will see the download link to datasheet in bottom of the page in this link.

http://www.simcom.us/product_detail.php?cid=1&pid=37

Image of our device is....

shivaaprs: The Arduino Mega has three additional serial ports: Serial1 on pins 19 (RX) and 18 (TX), Serial2 on pins 17 (RX) and 16 (TX), Serial3 on pins 15 (RX) and 14 (TX). [u]To use these pins to communicate with your personal computer, you will need an additional USB-to-serial adaptor, as they are not connected to the Mega's USB-to-serial adaptor[/u].

I suspect you are just being spooked by nothing of consequence, written by an idiot..

On a Uno, the single hardware serial communication port on D0,D1 is shared with the USB communication cable for the serial monitor i.e. the "communicate with your personal computer" alluded to above. This is the reason why you get a clash between a hardware serial device and the serial monitor. The Mega has four hardware serial ports. Port0 is on D0,D1 as usual, and the others on D14-19 as described. I submit the underlined admonition is pure gobbledygook, and the first question to ask is - why would you want to connect the PC thereto, when you can already do that with the existing USB cable in the normal manner? An advantage of the Mega is that you can have hardware serial items in service on pins D14-19 while still using the monitor but, no matter how many serial devices you have, there is surely never a reason for having the monitor on anything but the USB socket that it came with.

To use these pins to communicate with your personal computer, you will need an additional USB-to-serial adaptor, as they are not connected to the Mega's USB-to-serial adaptor. I suspect you are just being spooked by nothing of consequence, written by an idiot..

Why? That sentence is correct! You could argo that you don't need that but hei that is still valid if you want connect more than one device.If you want to connect that to another computer you will need the USB-Serial or if you want connect your SIM900 using his RS232 interface you will also need a converter

On a Uno, the single hardware serial communication port on D0,D1 is shared with the USB communication cable for the serial monitor

Shared with what? To me shared means two or more things at the same time.So you are sharing it with what? "Shared" is a very strong word when UART comunication enters in the game.

To use them to communicate with an external TTL serial device, connect the TX pin to your device's RX pin, the RX to your device's TX pin, and the ground of your Mega to your device's ground.

I didn't get the underlined statement...

It means if your modem has on the board TTL signals (RX and TX) you could wire it directly to you Mega Serial ports, if not then you will need a TTL/RS232 converter

see my connections are

I have connected gsm module Tx to Rx0 of the Arduino mega 2560 I have connected gsm module Rx to Tx0 of the Arduino mega 2560 I have given powersupply through adapter to gsm module.

My code is:

void setup() { Serial.begin(2400); //Baud rate of the GSM/GPRS Module Serial.print("\r"); delay(1000); Serial.print("AT+CMGF=1\r"); delay(1000); Serial.print("AT+CMGS=\"+919542081456\"\r"); //Number to which you want to send the sms delay(1000); Serial.print(" Hi \r"); //The text of the message to be sent delay(1000); Serial.write(0x1A); delay(1000); } void loop() { }

Programming successfully uploaded to Arduino But I am not receiving any msg...

what are the other things I need to consider about ?

This is a guess, but do you still have the USB cable connected to the PC? If so, disconnect. Using tx0,Rx0 is not unreasonable but, if you need the PC serial monitor connected, then connect the phone to Serial1 and change the relevant commands to Serial1.print(....

The picture is something i have never seen before, but I guess it is actually easier to connect to any serial you like, than my shield would be.