connecting GSM with Arduino

[phrbob93]

i have tried interfacing of gsm 900 module with Arduino uno
after reading some tutorial on the internet i found that sending "AT" as an AT command will give OK as a Result by the GSM Module

so i tried to send AT serially But I did not received any OK

heres my code

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Code C - [expand]
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#include <LiquidCrystal.h>
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
 
int led = 8;
// incoming serial byte
int inByte; 
void setup()
{
lcd.begin(16, 2);
// initialize the led pin as an output.
pinMode(led, OUTPUT); 
// start serial port at 9600 bps
Serial.begin(9600);
// wait for a while till the serial port is ready
delay(100);
// send the initial data once // 
Serial.print(" AT");
}
 
 
 
}
void loop()
{
// if we get a valid byte, read analog ins:
if(Serial.available())
{
// get incoming byte:
 
 
inByte= Serial.read(); 
Serial.write(inByte);
lcd.print(inByte);
// send the same character back to serial port
 
// blink the LED once // 
digitalWrite(led, LOW); 
delay(100); 
}
else
digitalWrite(led, HIGH);
while(1); 
}

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i did noticed that something is received as LED on pin 8 glows once
but why the recieved character cant be seened on lcd or either on the serial monitor screen????

 

[FvM]

i found that sending "AT" as an AT command will give OK as a Result by the GSM Module

Not exactly. AT must be followed by a carriage return character.

inByte= Serial.read(); 
Serial.write(inByte);

Why are you echoing incoming serial data back to serial output? Can cause endless ping-pong action.

Please notice that "AT"<CR> will be only understood by the modem if it's using the same baudrate. To utilize autobaud function, you must send separate characters "A", "T" and <CR> with inter-character delay.

 

[phrbob93]

how to send carriage return character <CR>

 

[Pulsetronics]

AT command with carriage Return(AT\r)

 

[FvM]

how to send carriage return character <CR>

Depends on language support.
- with println() procedure
- using \r control character in C strings
- using 0xd respectively decimal 13 ascii code.

 

[phrbob93]

dialing a number by hex keypad using gsm module 900 and arduino

i want to dial a number from hex keypad to call..
iam using interrupt method
hex keypad uses 74c922 keypad decoder ic
DA pin of 74c922 IC is connected to External interrupt pin 2
whenver the button is pressed an interrupt is invoked and the corresponding 4bit number reads by MCU at pin 4,5,6 and 7

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#include <LiquidCrystal.h>
LiquidCrystal lcd(13, 12, 11, 10, 9, 8);
 
// incoming serial byte
int number[10];    
int a, count=0;
void setup()
{
  lcd.begin(16, 2);
  for(int pin=3;pin<7;pin++)
{
  pinMode(pin, INPUT);
  }
  attachInterrupt(0, key, RISING);
  
  // start serial port at 9600 bps
  Serial.begin(9600);
  // wait for a while till the serial port is ready
  delay(100);
// send the initial data once //    
 }
 
void loop()
{ 
while(number[9]=='\0');    //wait till number array is full
                                   
 
 
lcd.clear();
  for(int i=0;i<10;i++)
  {
    lcd.print(number[i]);
  }
 
  Serial.print("ATD"); 
  
  delay(100);
  for(int i=0;i<10;i++)
  {
  Serial.print(number[i]);
  delay(30);
  }
serial.print(';');
 
   delay(100);
    Serial.write(13);
  delay(100);
 
    while(1);
}
void key()
{ 
  a=PIND&0xF0;
  a=a>>4;
  number[count++]=a;
  lcd.print(a); 
 
  
 }

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