gsm sim900

Using Arduino Programming Questions
1

i don't get text in the serial monitor i get ?

i have the gps sim 900 board from (Arduino GPRS Shield)
connected to the Arduino Uno board

the status lights are correct
power on
status light on
net light flashing slow

i can see the text is being received as the tx rx lights flash after send in the message and the power the gsm shield draws goes up to receive the message.

the code is below

any help much appreciated

thanks steve

//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);
unsigned char buffer[64]; // buffer array for data recieve over serial port
int count=0; // counter for buffer array
void setup()
{
GPRS.begin(19200); // the GPRS baud rate
Serial.begin(19200); // the Serial port of Arduino baud rate.
}
void loop()
{
if (GPRS.available()) // if date is comming from softwareserial port ==> data is comming from gprs shield
{
while(GPRS.available()) // reading data into char array
{
buffer[count++]=GPRS.read(); // writing data into array
if(count == 64)break;
}
Serial.write(buffer,count); // if no data transmission ends, write buffer to hardware serial port
clearBufferArray(); // call clearBufferArray function to clear the storaged data from the array
count = 0; // set counter of while loop to zero
}
if (Serial.available()) // if data is available on hardwareserial port ==> data is comming from PC or notebook
GPRS.write(Serial.read()); // write it to the GPRS shield
}
void clearBufferArray() // function to clear buffer array
{
for (int i=0; i<count;i++)
{ buffer*=NULL;} // clear all index of array with command NULL*
}

2 
unsigned char buffer[64]; // buffer array for data recieve over serial port

As opposed to the more usual signed char?

   buffer[count++]=GPRS.read();     // writing data into array

But failing to then NULL terminate the array.

Serial.write(buffer,count);            // if no data transmission ends, write buffer to hardware serial port

The comment is nonsense. Why not use Serial.print() to print the ASCII data in the array?

3

Thanks Paul

the script was from the web site for the board. So I used what was given.

Thanks for the pointers. I'm on it.
I still don't have the text recognised but i can see it moving from GPS to Arduino so its a step in the right direction. As I'm just starting out every step is big.