Make sure the pin isn't involved in JTAG, and that JTAG is disabled if 
it is.

Tony


Gordon Downie wrote:
> Hi All,
>
> I'm very new to PIC's and have started a small project where I want
> the PIC18 to be an I2C slave. I am prototyping my design on the PICKit
> 2 Low Pin Count Board with only the modifications described here.
>
> PIC : PIC18F13K22 and PIC16F690 (Obviously with different code / toolchain)
> Tool Chain : C18 with MPLAB
>
> Problem :
>
> I was unable to get the I2C Slave HW to Ack address bytes sent by an
> Aardvark USB to I2C and after a week went back to basics. On the
> prototype board I have removed the I2C connection (no other components
> / connections) and Pulled RB4 and RB6 High via 33K resistors. I have
> verified the resistance and voltage at the pin and both are correct
> (4.9v and 33kohm to Vdd), however when I read the port bits only RB6
> is high. It does not matter which bit I read first. I've swapped out
> to a different Chip and also switch to a different variant (PIC16F690)
> and re written the code below accordingly all with the same result so
> I'm confident I have missed something rather than a bad chip / board.
>
> #include <p18f13k22.h>   /* for TRIS and PORT declarations */
>
> #pragma config WDTEN = OFF
> #pragma config FOSC = IRCCLKOUT
> #pragma config PLLEN = ON
> #pragma config PCLKEN = ON
>
> #pragma config MCLRE = OFF
> #pragma config LVP = OFF
>
>
> #pragma code
> void main (void){
> 	unsigned int b = 0;
>
>   	// OSC
> 	OSCCON = 0b11111100; // 8 MHz internal oscillator
>
>     TRISC = 0x0;
>     TRISB = 0xFF;
>
> 	PORTC = 0;
>
> 	TRISBbits.TRISB4 = 1;
> 	TRISBbits.TRISB6 = 1;
>
> 	while(1){
>        //Display RB4 / RB6 on PORTC
> 		LATCbits.LATC0 = PORTBbits.RB4;
> 		LATCbits.LATC1 = PORTBbits.RB6;
>
>         //Heartbeat
> 		b++;
>     	if (b==0) LATCbits.LATC3 = !LATCbits.LATC3;
>     }
> }
>
>
> I am stumped. Any help / pointers gratefully received.
>
> Many thanks,
> Gordon
>   
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