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I've been googling for about two weeks now and I still can't seem to get my I2C working. I've used this (what seems to be complete) tutorial. I followed the Master Write and Master Read examples to try and read from my sensor. I've referenced the I2C_MASTER.zip and I2C_SLAVE.zip from the Microchip site, and my I2C still does not work. Can I get some tips?

More information:

  • SDA, SCL hooked up to PIC18F's SDA1/SCL1, configured for open-drain and wired to supply voltage
  • Tried different approaches with IdleI2C1() and EEAckPolling1(address) with no progress
  • Followed the Microchip example of checking the collision bit, but still doesn't work
  • Using i2c.h from the XC8 Compiler
  • SSP1ADD is set to 19, but maybe it's not right? I have my clock running at 8 Mhz with the internal oscillator, and got that value using Fclock = Fosc / (( SSPxADD + 1 ) * 4), where Fclock is 100 kHz and Fosc is 8 Mhz
  • I do not have an oscilloscope to view signals

Does anyone know of any libraries I can easily use for reading and writing without worrying about Ack/Nack signals?

Here's the relevant code:

void init()
{
    CloseI2C1();
    OpenI2C1(MASTER,SLEW_OFF);
    SSP1ADD = 19;

    getEEPROM();
}

void getEEPROM()
{
    static signed char status,data;
    IdleI2C1();
    StartI2C1();
    while(SSPCON2bits.SEN);
    do{
        status = WriteI2C1(MLX_EEPROM_WRITE);// Signal to EEPROM start point
        if(status == -1)
        {
            data = SSPBUF;
            SSPCON1bits.WCOL = 0;
        }
    }while(status!=0);
    IdleI2C1();
    do{
        status = WriteI2C1(0x00);// Signal to EEPROM start point
        if(status == -1)
        {
            data = SSPBUF;
            SSPCON1bits.WCOL = 0;
        }
    }while(status!=0);
    IdleI2C1();
    RestartI2C(); 
    do{
        status = WriteI2C1(MLX_EEPROM_READ);// Signal to EEPROM start point
        if(status == -1)
        {
            data = SSPBUF;
            SSPCON1bits.WCOL = 0;
        }
    }while(status!=0);
    IdleI2C1();
    getsI2C1(eepromData,255);
    /* // supposed to be the same as getsI2C1
    for(i = 0; i < 256; i++)
    {
        eepromData[i] = ReadI2C1();
        IdleI2C1();
    }
   */
    NotAckI2C();
    while ( SSPCON2bits.ACKEN );
    StopI2C();
    while ( SSPCON2bits.PEN );
}
Community
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WayneDinh
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  • "SDA, SCL hooked up to PIC18F's SDA1/SCL1, configured for open-drain and wired to supply voltage." Are you wiring these directly to the supply voltage, or are you using pullup resistors? If it's direct, those pins have probably been damaged. – bitsmack Apr 10 '14 at 06:49

1 Answers1

1

Start simple, see if you can get an ack from the device, the proceed further. Here is some working code from a pic18f87j50.

void InitEEprom(void) {
    TRISDbits.TRISD6 = 0;
    TRISDbits.TRISD5 = 1;
    OpenI2C2(MASTER, SLEW_OFF);
    SSP2ADD = 0x36;
}

int FindDevice(unsigned char Control) {
    unsigned int ErrorCode;
    IdleI2C2(); //Ensure Module is Idle
    StartI2C2(); //Generate Start COndition
    SSP2BUF = Control;
    //WriteI2C2(Control); //Write Control byte
    IdleI2C2();
    ErrorCode = ACKStatus();
    StopI2C2();
    return ErrorCode; //Return ACK Status
}
Erik Friesen
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