GSM problems with AT commands

[Ed_Banses]

Hi everybody,

I am starting a project trying to communicate a PIC16F877A with a GSM modem Fargo Maestro 100.
I want to send a message and I can do it by using a PC connected by hyper terminal with the modem.
The problem arrives when I try to connect the PIC with the MODEM, y cannot send the message, there is teh code:

#include <16f877A.h>
#device ICD=TRUE
#fuses HS,NOLVP,NOWDT,PUT
#use delay(clock=20000000)
#use rs232(baud=115200, xmit=PIN_C6, rcv=PIN_C7, bits=8, stream=GPS)

const int CR=0x0d;

void main() {

fprintf(GPS,"AT+CMGF=1");
fputc(CR,GPS);
fprintf(GPS,"AT+CMGS=\"+44788614354\"");
fputc(CR,GPS);

delay_ms(1000);
fprintf(GPS,"Hi world");

fputc(0x1A,GPS);
delay_ms(1000);
putc(CR);
}

Thanks a lot just for reading.
Looking forward any idea.
Eduardo

[Ttelmah]

Add ERRORS to the RS232 statement. Though it doesn't matter at present, the UART receive side will be 'hung' after the code, since the incoming data has not been processed.

Add:
while(true);

After your last putc, otherwise the last characters will never be sent, as the PIC will run off the end, and go to sleep.

Why are you using 'putc' here, not fputc?.

Seriously, look at your hardware. Remember that the PC, generates RS232, while the PIC develops TTL serial. You need signal inversion, and level shifting to match what the PC generates.

Best Wishes

[Ed_Banses]

Thanks a lot for the reply Ttelmah

I have just included the task in a while loop, the sms should be sended when I press a button and wait until the next time I will press it.
In addition to this I changed the last putc with a fputc.
But the application is still not working.
Could you tell me how can I add the ERRORS to the RS232 statements?
Can I use the virtual RS232 of the ICD-4000 as a monitor for the messages of the modem?
Thanks a lot.
Eduardo

[arunb]

Hi,

How are you trying to receive the data from GSM. ??

You should use the receive interrupt for this, after the interrupt has occurred , you should read the entire string...

thanks
arunb

[Foppie]

[Ed_Banses]

Thanks a lot for your ideas, I will try them!!
I will tell you how is going everything.
Thanks a lot again,
Eduardo

[r520m]

Hi

1.- Try to use baud=9600, up to 57600.
2.- Try to comunicate PC with 16F877 using 9600 up to 57600, using max232.
If your hyperterminal receives the chars sent, your PIC is working very well. So you will can comunicate PIC to modem.
3.- If you can´t receive data from PIC on PC, the hardware UART is not workink.
4.- Try to use "force_sw" in use rs232 definition, for UART pins be have a software behavoir.

5.- If 4 point not works, try use another pins of PIC...

6.- IN your code there is not rutine for receive data from modem, example, send AT<CR>, modem answers with AT....may be modem is working, but the code have faults...

An question:

Modem works in RS232 or TTL levesl?



Sorry for my bad english


Bye

[r520m]

Hi again:

from www.fargo.com

[Ed_Banses]

Thanks a lot for your responses.
Unfortunately I am still without communication :(
I wrote the next code in order to check the communication with the modem:

[r520m]

First, tell us what are you doing, do you use max232 bettwen PIC and your modem?

Bye

[Ed_Banses]

Well, I am using the evaluation board of CCS for the PIC16F877 microcontroller.
Mainly is the PIC connected to a MAX232 and y connected the Max In/Out to the MODEM.
Thanks a lot.
Regards,
Eduardo

[Ttelmah]

A couple of obvious questions at this point. Ae you connecting the ground wire as well?. It is needed.
Are you sure you have the TX/RX connected the right way round?. Remember that the if the PIC is normally connected to the PC, it'll have it's 'TX' pin, connected to the PC's 'RX' pin, and vice versa. The Modem will be the same (they are both technically wired as DCE devices). You will actually need a 'null modem' cable, to allow the units to connect to each other.

Best Wishes

[Victor]

To read incoming sms, I can use AT+CMGL, but I must poll it often.
Can I get any trigger message if there is new incoming SMS?
I am using TC35i.

Thank you.