i2c.c

/*! \file i2c.c \brief I2C Interface Driver for Atmel AT91. */
//*****************************************************************************
//
// File Name    : 'i2c.c'
// Title        : I2C Interface Driver for Atmel AT91
// Author       : Pascal Stang - Copyright (C) 2005-2006
// Created      : 12/10/2005
// Revised      : 10/22/2006
// Version      : 0.1
// Target MCU   : Atmel AT91 series
// Editor Tabs  : 4
//
// This code is distributed under the GNU Public License
//      which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************

// system includes
#include "at91sam7s64.h"
#include "global.h"

// local includes
#include "rprintf.h"
#include "timer.h"
#include "i2c.h"

// functions
void i2cInit(void)
{
    // set I/O pins for I2C
    *AT91C_PIOA_PDR = AT91C_PA3_TWD | AT91C_PA4_TWCK;
    *AT91C_PIOA_ASR = AT91C_PA3_TWD | AT91C_PA4_TWCK;
    // and set for open-drain
    *AT91C_PIOA_MDER = AT91C_PA3_TWD | AT91C_PA4_TWCK;

    // turn on clock into I2C system
    AT91C_BASE_PMC->PMC_PCER = (1<<AT91C_ID_TWI);

    // disable interrupt handling
    //*AT91C_AIC_IDCR = 0xFFFFFFFF;

    // set bitrate
    AT91C_BASE_TWI->TWI_CWGR = 0x0001C0C0;
    //AT91C_BASE_TWI->TWI_CWGR = 0x0000C0C0;

    // initialize interface
    AT91C_BASE_TWI->TWI_CR = AT91C_TWI_MSEN;
}

int i2cMasterSend(u08 deviceAddr, u08 length, u08 *data)
{
    int status;

    // prepare write transmission
    AT91C_BASE_TWI->TWI_MMR = deviceAddr<<16;
    // set slave device internal address
    //AT91C_BASE_TWI->TWI_IADR = 0x10;
    if(length)
    {
        // load transmit holding register
        AT91C_BASE_TWI->TWI_THR = *data++;
        length--;
    }
    // send start condition
    AT91C_BASE_TWI->TWI_CR = AT91C_TWI_START;
    // wait for complete (or no device)
    do
    {
        // required in order for NACK (dev not present) to be detected and work
        delay_us(50);
        // check status
        status = AT91C_BASE_TWI->TWI_SR;
        // watch for address NACK
        if(status & AT91C_TWI_NACK)
            return I2C_ERROR_NODEV;
    } while(!(status & AT91C_TWI_TXRDY));
    // send more data
    while(length)
    {
        // load transmit holding register
        AT91C_BASE_TWI->TWI_THR = *data++;
        length--;
        // wait for complete
        while(!(AT91C_BASE_TWI->TWI_SR & AT91C_TWI_TXRDY));
    }
    // send stop condition
    AT91C_BASE_TWI->TWI_CR = AT91C_TWI_STOP;
    // wait for trasmission complete
    while(!(AT91C_BASE_TWI->TWI_SR & AT91C_TWI_TXCOMP));
    // return ACK/NACK status
    return (AT91C_BASE_TWI->TWI_SR & AT91C_TWI_NACK);
}

int i2cMasterReceive(u08 deviceAddr, u08 length, u08 *data)
{
    int status;

    // prepare read transmission
    AT91C_BASE_TWI->TWI_MMR = (deviceAddr<<16) | AT91C_TWI_MREAD;
    // dummy read the receive holding register
    AT91C_BASE_TWI->TWI_RHR;
    // set slave device internal address
    //AT91C_BASE_TWI->TWI_IADR = 0x10;
    // send start condition
    AT91C_BASE_TWI->TWI_CR = AT91C_TWI_START;
    // wait for complete (or no device)
    do
    {
        // required in order for NACK (dev not present) to be detected and work
        delay_us(50);
        // check status
        status = AT91C_BASE_TWI->TWI_SR;
        // watch for address NACK
        if(status & AT91C_TWI_NACK)
            return I2C_ERROR_NODEV;
    } while(!(status & AT91C_TWI_RXRDY));
    // receive data
    while(length)
    {
        // load transmit holding register
         *data++ = AT91C_BASE_TWI->TWI_RHR;
        length--;
        // wait for complete
        while(!(AT91C_BASE_TWI->TWI_SR & AT91C_TWI_RXRDY));
    }
    // send stop condition
    AT91C_BASE_TWI->TWI_CR = AT91C_TWI_STOP;
    // wait for trasmission complete
    while(!(AT91C_BASE_TWI->TWI_SR & AT91C_TWI_TXCOMP));
    // return ACK/NACK status
    return (AT91C_BASE_TWI->TWI_SR & AT91C_TWI_NACK);
}


void i2cScanBus(void)
{
    int i;
    u08 packet[1];


    for(i=1; i<128; i++)
    {
        if(!i2cMasterSend(i, 1, packet))
            rprintf("I2C Device addr 0x%x -> PRESENT\n", i);
        else
            rprintf("I2C Device addr 0x%x -> NACK\n", i);
    }
}

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