Dear sir,

I face problem in sending sms from modem which connect with microcontroller throgh Rx,Tx & gnd.
when i send AT+CMGF=1,it retuns OK.but when i send AT+CMGS=9377733199<message><ctrl+z> ,it returns ERROR.


send[0]='A';
send[1]='T';
send[2]='+';
send[3]='C';
send[4]='M';
send[5]='G';
send[6]='S';
send[7]='=';
send[8]='9';
send[9]='3';
send[10]='7';
send[11]='7';
send[12]='7';
send[13]='3';
send[14]='3';
send[15]='1';
send[16]='9';
send[17]='9';
send[18]='\r';
send[19]='G';
send[20]='S';
send[21]='M';
send[22]=0x1a;
send[23]=';';
send[24]='\r';

while(*(send+j))
{
R_UART0_Send(send+j,1);
for(k=0;k<60000;k++);
j++;
}
j=0;


Pls. guide me.

The 8051 Primer board is specifically designed to help students to master the required skills in the area of embedded systems. The kit is designed in such way that all the possible features of the microcontroller will be easily used by the students. The kit supports in system programming (ISP) which is done through serial port.

NXP’s 8051 (89V51RD2), 8051 Primer Kit is proposed to smooth the progress of developing and debugging of various designs encompassing of High speed 8-bit Microcontrollers.

GSM (Global System for Mobile Communication)

GSM is a digital mobile telephony system. GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band.

Interfacing GSM

Fig. 1 shows how to interface the GSM with microcontroller. The GSM module is communicate the microcontroller with mobile phones through UART. To communicate over UART or USART, we just need three basic signals which are namely, RXD (receive), TXD (transmit), GND (common ground).

GSM modem interfacing with microcontroller for SMS control of industrial equipments. The sending SMS through GSM modem when interfaced with microcontroller or PC is much simpler as compared with sending SMS through UART.

Text message may be sent through the modem by interfacing only three signals of the serial interface of modem with microcontroller i.e., TxD, RxD and GND. In this scheme RTS and CTS signals of serial port interface of GSM Modem are connected with each other.

The transmit signal of serial port of microcontroller is connected with transmit signal (TxD) of the serial interface of GSM Modem while receive signal of microcontroller serial port is connected with receive signal (RxD) of serial interface of GSM Modem.

The SMS message in text mode can contain only 140 characters at the most. It depends upon the amount of information collected from GPS Engine that you need at the base station for tracking vehicle or person.