Ladies and Gents,

In between my hand are the following (also see images below) :
- PIC18f2580, Pickit2
- PICKkit Serial I2C Demo board (using 8bit I/O Expander MCP23008) input two wires I2C and outputed to 8 leds
- MPLABX, COMPILER : xC8

I got the code well written (in my opinion) based on my studies of PIC18f datasheet and MCP23008... I can't figure why the leds aren't getting lit. I tested SDA and SDL on oscilloscope and they are constant 5v.
Am I missing anything in the code? or is the expander burnt ? , or maybe I'm not generating a clock ?
I would appreciate your comments

#include <xc.h>
#include <i2c.h>
#include <delays.h>
#include <p18f2580.h>
#include <stdio.h>
#include <stdlib.h>

//Set configuratie bits
#pragma config OSC = HS         // HS oscillator, at C3 and C4= 22pF, crystal written on it 20MHz but I assume its 16MHz, P29 Table 3-1
#pragma config WDT = OFF          // Watchdog Timer disabled
#pragma config LVP = OFF          // Low Voltage ICSP disabled

#define WRITE 0xFE        // bitmask for writes
#define READ 0x01        // bitmask for reads

//Define MCP23008 Multiplexer to LEds
// Microchip MCP23008 8?bit I/O Expander
#define MCP23008_ADDR 0x40 // MCP23008 Device Identifier
#define IODIR 0x00 // MCP23008 I/O Direction Register set as output
#define GPIO 0x09 // MCP23008 General Purpose I/O Register
//#define OLAT 0x0A // MCP23008 Output Latch Register

  

void main(void)
{

    CloseI2C(); // close if was opened
    SSPCON1 = 0x28; //0010 1000// Enable SDA and SCL, I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))
    SSPCON2 = 0x00; // Reset MSSP Control Register
    SSPADD =  39; // 31, I2C Preload Clock 100kHz by 48MHz...Standard I2C Clock speed: 100 kHz
    // SSPAD=( Fosc/(4*I^C*clock) ) -1 For 20 MHz, the value is 49, for 40 MHz the value is 9
//    SSPCON1bits.SSPEN = 1;
  //    SSPSTAT = 0x80;
    TRISCbits.TRISC3=1; //SDA
    TRISCbits.TRISC4=1; //SLK
  
    OpenI2C(MASTER, SLEW_OFF); //init i2c SLEW_OFF= SSPSTAT=0x80
    Delay1KTCYx(550); // 1000 * 550 * (1/12) us = 50ms
    StartI2C(); //give start I2C
    // while(SSPCON2bits.SEN);//wait until start condition passes ---> this line is already defined and included in StartI2C4
    WriteI2C(MCP23008_ADDR & WRITE); //mcp23008 device opcode adres 0x40 + write
    WriteI2C(IODIR); //access mcp23008 register address 0 (IODIR) I/O register
    WriteI2C(0x00); //all IO pin's as output
    StopI2C();
    CloseI2C(); // close if was opened
  
    while(1)
    {
         Delay1KTCYx(550); // 1000 * 550 * (1/12) us = 50ms
         StartI2C();
         WriteI2C(MCP23008_ADDR & WRITE); //mcp23008 device opcode adres 0x40
        //while(SSPCON2bits.ACKSTAT==1); // wait till ACK was received from slav
        WriteI2C(GPIO); //access mcp23008 register address 9 (GPIO) to read or write
        //while(SSPCON2bits.ACKSTAT==1); // wait till ACK was received from slave
        WriteI2C(0xFF); //All GPIO output are set to high
        StopI2C(); //SSPCON2bits.PEN = 1;            // initiate bus stop condition
        CloseI2C();
    }
}

/*
// Enable Receive Mode
SSPCON2bits.RCEN = 1; // Enable master for 1 byte reception
while(!SSPSTATbits.BF); // Wait until buffer is full
return(SSPBUF);*/

 

Have you gone through the basic debugging steps? Is the processor doing anything?

If you have, try the following:

• Try a check to see if WCOL is getting set on your first write to SSPBUF, the datasheets l datasheet makes note of this on page 213.
• Set the TRISC<3:4> bits before configuring the MSSP for I2C.
• Verify you have appropriate pull up resistors on SDA and SCK.

This is why I don't use the compiler functions, it makes it hard to see what they're doing to debug.

 

Have you gone through the basic debugging steps? Is the processor doing anything?

If you have, try the following:

• Try a check to see if WCOL is getting set on your first write to SSPBUF, the datasheets l datasheet makes note of this on page 213.
• Set the TRISC<3:4> bits before configuring the MSSP for I2C.
• Verify you have appropriate pull up resistors on SDA and SCK.

This is why I don't use the compiler functions, it makes it hard to see what they're doing to debug.

I just started debugging after the post. First time I do it... not so handy with it ... The debugger gets stuck in StartI2C() function (using step into), meaning that SDA isn't pulled low for start bit! --> as the oscilloscope shows

TRISCC<3:4> is set in the code I had, and also set in function OpenI2C , ...... WCOL condition is included in WriteI2C. Following is description of the first few functions

I was pretty desperate, I connected the board to Arduino... Yet no results.. I think the chip is burnt. Is there a way to test it ?

CloseI2C();

void CloseI2C( void )
{
  SSPCON1 &= 0xDF;                // disable synchronous serial port
}

OpenI2C

void OpenI2C( unsigned char sync_mode, unsigned char slew )
{
  SSPSTAT &= 0x3F;                // power on state
  SSPCON1 = 0x00;                 // power on state
  SSPCON2 = 0x00;                 // power on state
  SSPCON1 |= sync_mode;           // select serial mode
  SSPSTAT |= slew;                // slew rate on/off

  I2C_SCL = 1;
  I2C_SDA = 1;
  SSPCON1 |= SSPENB;              // enable synchronous serial port

}

I2CStart();

     SSPCON2bits.SEN=1;
     while(SSPCON2bits.SEN); //wait until start condition clears to allow data transmittion

Here is the modified code

//compiler XC8

#include <xc.h>
#include <i2c.h>
#include <delays.h>
#include <p18f2580.h>
#include <stdio.h>
#include <stdlib.h>

//Set configuratie bits
#pragma config OSC = HS         // HS oscillator, 22pF, 16MHz, P29 Table 3-1
#pragma config WDT = OFF          // Watchdog Timer disabled
#pragma config LVP = OFF          // Low Voltage ICSP disabled

#define WRITE 0xFE        // bitmask for writes
#define READ 0x01        // bitmask for reads
//#define I2C_IO_V5       // TRISC=24; I2C pins


// Microchip MCP23008 8?bit I/O Expander
#define MCP23008_ADDR 0x40 // MCP23008 Device Identifier
#define IODIR 0x00 // MCP23008 I/O Direction Register set as output
#define GPIO 0x09 // MCP23008 General Purpose I/O Register
//#define OLAT 0x0A // MCP23008 Output Latch Register

void main(void)
{

    CloseI2C(); // close if was opened
  
    SSPADD =  39; // 31, I2C Preload Clock 100kHz by 48MHz...Standard I2C Clock speed: 100 kHz
    // SSPAD=( Fosc/(4*I^C*clock) ) -1 For 20 MHz, the value is 49, for 40 MHz the value is 9

    TRISCbits.TRISC3=1; //SDA
    TRISCbits.TRISC4=1; //SLK
   
    OpenI2C(MASTER, SLEW_OFF); //init i2c SLEW_OFF= SSPSTAT=0x80  SSPCON1 = 0x28; //0010 1000// Enable SDA and SCL, I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))     SSPCON2 = 0x00; // Reset MSSP Control Register
    Delay10TCYx(12); // 10 * 12 * (1/12) us = 10us --> time for counter to count based on baud rate 100kHz
    StartI2C();
    WriteI2C(MCP23008_ADDR);// & WRITE); //mcp23008 device opcode adres 0x40 + write
    WriteI2C(IODIR); //access mcp23008 register address 0 (IODIR) I/O register
    WriteI2C(0x00); //all IO pin's as output
    StopI2C();
    CloseI2C(); // close if was opened
   
    while(1)
   {
    
         Delay10TCYx(12); // 1000 * 550 * (1/12) us = 50ms
         StartI2C();
        WriteI2C(MCP23008_ADDR & WRITE); //mcp23008 device opcode adres 0x40
  //  while(SSPCON2bits.ACKSTAT==1); // wait till ACK was received from slav
         WriteI2C(GPIO); //access mcp23008 register address 9 (  GPIO) to read or write
   // while(SSPCON2bits.ACKSTAT==1); // wait till ACK was received from slave
    //can you combine the previous function with this ? what happens after transmitting first 8 bits
         WriteI2C(0x00); //All GPIO output
         StopI2C(); //SSPCON2bits.PEN = 1;            // initiate bus stop condition
         CloseI2C();
    }
}