Hi, I can send the command "AT+CMGR=1" To GSM modem, but after that i cannot access the message from it. The modem is "Iwow" and microcontroller is 89c52. I have used Tx, Rx and ground pin of RS232. whether it is necessary to use RTS and CTS pins for this modem? When i send the command "AT+CMGR=1" to GSM modem, a pulse will be coming at TI pin of microcontroller. meanwhile there is no pulse at RI pin, indicating no message has been retrieved from GSM modem. But if i connect it to Hyperterminal i can read the message.
Please find a solution to this problem..
I have used Tx, Rx and ground pin of RS232. whether it is necessary to use RTS and CTS pins for this modem?
Did you take into account that the pins on the microcontroller do not have RS-232 voltage levels, and that a RS-232 transceiver (e.g. MAX232) may be necessary to interface the microcontroller to a RS-232 device ?
In the worst case, directly connecting the microcontrollers RX and TX lines to RS-232 voltage levels can damage the microcontroller.
I have used MAX232 as a transceiver( To convert to TTL LEVEL). Programming is done using C code. When i send the AT command like, AT+CMGR=1 a pulse wil be observed at TI pin of Microcontoller(checked using digital probe). But later, pulse is not observed at RI pin.since there is no indication of data at RI pin, the program will halt at the statement- while(RI==0);
wether GSM modem is not accepting that format?( GSM Modem used is of 'IWOW').