i cant interface NXP2148 with the GSM module. i have used the UART1 (through RS232 DB9 using RXD, TXD and ground) to interface with the GSM module at 9600. when i send the command AT<CR> through hyperterminal it accepts, sends back an OK when i SEND the same command through NXP2148 there is no response. my program is correct i have checked it at the hyperterminal. And i tried changing the cable also... but still no response. PLEASE HEPL!!!!
DO you have a proper RS232 transceiver in place?
Are you certain that the cable connections are correct? Remember that the modem is a DCE, and TX is an input on a DCE...
Does the modem require any/all of the modem control lines (RTS, CTS, etc)? If so, have you correctly implemented them.
"when i SEND the same command through NXP2148 there is no response."
That could be any number of things:
1. The MCU is not sending at all;
2. The MCU is sending, but it is not (quite) right;
3. The signal is not reaching the DCE;
4. The signal is reaching the DCE, but it's not listening;
5. The DCE is receiving the signal, but it is ignoring it;
6. The DCE is responding, but the response is not reaching the MCU;
7. The response is reaching the MCU, but your software is not (correctly) recognising it
etc, etc,...
i got the problem... DTR signal should have been LOW only in my board it is about +9V. THANKs A LOT for your help...
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