Hello, I'm having some issues with baudrate problems when sending serial data from my PC to my PIC using bluetooth. Any help is much appreciated.

Basically, I have a PIC dev board with the TX and RX lines tied to a bluetooth module. I can connect to the module through a USB module on my computer. Here is the example program that came with the board.

/*
Code Support     : Board ET-USBPIC/4550
Compiler         : PIC C Compiler Version 3.249
Micro Controller : PIC18F4550
OSC              : 48MHz
*/    

#include <18F4550.h>
#fuses HSPLL,USBDIV,PLL5,CPUDIV1,VREGEN,NOWDT,NOPROTECT,NOLVP,NODEBUG
#use delay(clock=48000000)

#define TX1   PIN_C6
#define RX1   PIN_C7

#use rs232(baud = 9600, xmit = TX1, rcv = RX1)


#use fast_io(C)


void main() {

  char Dat;

      set_tris_c(0B10000000);


   While (1)
   {
     delay_ms(2); 
     putc('B'); 
     delay_ms(2); 
     putc('A');
   }
}

The bluetooth module has a command interface. The default baudrate is 115200, and I set that to 9600. Using PuTTY as a terminal, I also set the serial settings to 9600. Everything is set the same: 8 bits, 1 stop bit, no parity, no flow control.

On output, instead of getting "A"'s and "B"'s, I get stuff like:

¿ñ×ö¿¿ñ×ö¿¿ñ×ö¿¿ñ×ö

If anyone can help, that'd be great.

 

That sounds like a baud rate problem giving you garbled data. The code was written for a PIC18F4550 but you say you are using a PIC18F458 and don't spec a frequency. The line:

#use delay(clock=48000000)

tells the compiler the hardware clock speed, and it needs to match.

 

Yes, this is true. I changed to #use delay(clock=10Mhz), changed the header to be for the correct pic. changed the fuse to be HS instead of HSPLL, but am still having the same issues.

I'm working on a dev board, but they didn't give me any sample code to work with for this board. they had it for the PIC18f4550, but that's it.

 

Do you have a max232 on hand? If so what happens when you wire direct through the max232?

 

Do you have a max232 on hand? If so what happens when you wire direct through the max232?

I have my PIC which has the TX/RX lines correctly mapped to the max232. Thats part of the dev board. Then I wired my TX,RX lines of my bluetooth to the max232.

EDIT: Okay, since I'm a beginner I couldn't really understand this very well. But I think I'm getting closer. I'm using this bluetooth module :

http://www.sparkfun.com/products/10269

And I'm using this dev board:

http://www.futurlec.com/PIC18F458_Development_Board.shtml

On the bluetooth page I couldn't understand what they meant when they say that you cannot map the bluetooth directly to a serial port, you need a max232. However, after I took out the max232 on my dev board and shorted the connections, I was able to get the correct outputs.

 

Double (and triple) check the "#fuses" settings to insure the instruction rate is what you want. Same for OSCCON.

It's not such a bad idea to write a test program to exercise a pin and check it on a scope to make sure things run as fast as you think they do.