GSM Alarm

Hi! I am a beginers pIC developments circuits and I work in an GSM alarm whit PIC 16F84A and an telephone sony ericsson T226 or K300a. I test both whit hyperterminal of windows and work ok! receives and sent ok the AT Commands, displays the correct string on the screen, but when I try to probe whit PIC the sony ericsson dont receive the AT commands. I use a subroutine for transmit AT commands to the phone at 9600 bps. How is the correct way to send characters ASCII? ..... MOVLW "A" , CALL XMIT_RS232 , MOVLW "T" , CALL XMIT_RS232 and so on.?? please help me.

thanks in advance
jose

I think that problem could be in the connection of the pic to the phone, someone can tell me a circuit between a pic and a cell phone T226??

The basic idea you have is right, to transmit each character in turn.

I assume that you have some sort of level converter.

Some GSM phones are very sensitive to the timing of the serial port. A 16F84 is a bad choice of PIC, as it doesn't have a EUSART, so you have to be bit-bashing.

If you use a 16F628A, it is cheaper, and it has a EUSART.

You can monitor what the PIC is sending to the GSM phone with hyperterminal.