[SOLVED] how to interface gsm modem to microcontroller via RS232?

[diannejose]

i have connected the RS232 pin as TX-RX AND RX-TX AND ALSO THE GROUND. I am using ARM micro controller. I am not able to receive data from mobile to the micro controller.please help in interfacing modem with the microcontroller.

 

[ansarmytheen]

Dear friend,

May be your modem works only in Null modem concept.So connect rs232 in null modem setup.

 

[ckshivaram]

1. check modem with hyperterminal
2. write UARt prg to check tx and rx functionality of UART in your controller
3. Interface modem to UART0 of controller and program for uart0
4. even if it does not work post your code here

 

[nikhilele]

i have connected the RS232 pin as TX-RX AND RX-TX AND ALSO THE GROUND. I am using ARM micro controller. I am not able to receive data from mobile to the micro controller.please help in interfacing modem with the microcontroller.

Always first check Modem using Hyperterminal
just try AT command and u should get OK responsed from modem...


plz mention Which modem you are using...

 

[otuzsubat]

connect RX to RX, and TX to TX, also GND. this is null modem connection

 

[diannejose]

i am using the Pulraj gsm modem.
the modem is working properly if we connect it to the hyper terminal. when i interface the modem to the micro controller, i can't get the signal from the modem to the micro controller, but i am able to pass command from the micro controller to the gsm modem.(like sending message via RxTx, TxRx connection and GND ). the code is working properly if we enter gsm data via hyper terminal

 

[ansarmytheen]

Dear friend,

i think your modem works only in null modem concept( Micro controller to GSM not pc to gsm).

 

[ckshivaram]

Is it the same cable you are using to connect GSM and PC for testing. And is it the same cable used to connect GSM and micro. Check some modems use cross cable like wavecom. check and update back. If it is same cable then your coding mistake. check the hardware cable connection, if it is correct then post your code.

 

[diannejose]

for checking PC with GSM i used RX-RX and Tx-Tx. and for microcontroller and modem i used Rx-Tx and Tx-Rx

 

[ansarmytheen]

Hai

Look my attach.

 

[ckshivaram]

for checking PC with GSM i used RX-RX and Tx-Tx. and for microcontroller and modem i used Rx-Tx and Tx-Rx

Maintain same connection between controller and GSM as you do for testing PC and GSM.

---------- Post added at 21:48 ---------- Previous post was at 21:44 ----------

Some modem need cross cable and some use straight. Like simcom use cross and wavecom uses straight, their internal track wiring are a bit different. Wavecom serial cable connection is different with respect to 2, 3 compared to available serial cable

 

[diannejose]

do we have to do any other settings other than (U1LCR & U1DLL) in UART1 of microcontroller

 

[ckshivaram]

can you post your code so that we can help you

 

[diannejose]

i have included a lpc2129 code in which i want to read message from SIM using AT+CMGR=1 command through external interrupt and UART1 interrupt