twi_lib.c

单片机开发程序原码,仅供个人学习参考. 各原码详细功能见压缩包及代码注释.

/*C**************************************************************************
* NAME:         twi_lib.c
*----------------------------------------------------------------------------
* Copyright (c) 2003 Atmel.
*----------------------------------------------------------------------------
* RELEASE:      snd1c-refd-nf-4_0_3
* REVISION:     1.3
*----------------------------------------------------------------------------
* PURPOSE:
* This file provides all minimal functionnal access to the I2C interface 
*****************************************************************************/

/*_____ I N C L U D E S ____________________________________________________*/

#include "config.h"                         /* system configuration */


/*_____ M A C R O S ________________________________________________________*/


/*_____ D E F I N I T I O N ________________________________________________*/

volatile bit b_I2C_busy;
volatile unsigned char I2C_Err;
volatile unsigned char I2C_nb_transmited;
volatile unsigned char I2C_RecPtr;

/*_____ D E C L A R A T I O N ______________________________________________*/


/*V**************************************************************************
* NAME: I2C_slave_data[I2C_NB_SLAVE_DATA] 
*----------------------------------------------------------------------------
* PURPOSE: 
* Global public Variable for I2C message in slave mode
*****************************************************************************/
volatile unsigned char xdata I2C_slave_data[I2C_NB_SLAVE_DATA];

/*V**************************************************************************
* NAME: I2C_message
*----------------------------------------------------------------------------
* PURPOSE: 
* Global public Variable for I2C message in master mode
*****************************************************************************/
volatile I2C_type_message xdata	I2C_message;


/*F**************************************************************************
* NAME: i2c_baud_rate 
*----------------------------------------------------------------------------
* PARAMS:
* return:  value for CR2..CR0 
*----------------------------------------------------------------------------
* PURPOSE: 
* returns correct value for CR2..CR0.
*----------------------------------------------------------------------------
* EXAMPLE:
* SSCON |= i2c_baud_rate(256);
*----------------------------------------------------------------------------
* NOTE: 
*----------------------------------------------------------------------------
* REQUIREMENTS: 
*****************************************************************************/
unsigned char i2C_baud_rate (unsigned int ratio)
{
  switch ( ratio )
  {
    case 256:
      return I2C_RATIO_256;
    break;

    case 224:
      return I2C_RATIO_224;
    break;

    case 192:
     return I2C_RATIO_192;
    break;

    case 160:
      return I2C_RATIO_160;
    break;

    case 960:
      return I2C_RATIO_960;
    break;

    case 120:
      return I2C_RATIO_120;
    break;

    case 60:
      return I2C_RATIO_60;
    break;
    }
}
	


/*F**************************************************************************
* NAME: I2C_decode_status 
*----------------------------------------------------------------------------
* PARAMS:
* return:  none
*----------------------------------------------------------------------------
* PURPOSE: 
* main processing state machine for I2C message reception transmission
* in slave or master mode.
* This function is called when an event occured on the I2C interface.
* Can be used both in polling or interrupt mode.
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE: 
*----------------------------------------------------------------------------
* REQUIREMENTS: 
*****************************************************************************/
void I2C_decode_status (void)
{
  switch (SSSTA)
  {
    //  STATE 00h: Bus Error has occurred 
    //  ACTION:    Enter not addressed SLV mode and release bus
    case  0x00 :
      b_I2C_busy = FALSE;
      I2C_Err  = BusError;
    break;

    //STATE 08h: A start condition has been sent
    //ACTION:    SLR+R/W are transmitted, ACK bit received
    case 0x08 :
      I2C_CLEAR_START;
      SSDAT = I2C_message.address<<1;
      if ( I2C_message.rw == I2C_READ )	SSDAT++; // Add 1 for Read bit in AdrWord
      I2C_SET_AA;
      //from here to 0x18 transmit or 0x40 receive                 
    break;

    //STATE 10h: A repeated start condition has been sent
    //ACTION:    SLR+R/W are transmitted, ACK bit received
    case 0x10 :
      I2C_CLEAR_START;              // Reset STA bit in SSCON
      SSDAT = I2C_message.address<<1;
      if ( I2C_message.rw == I2C_READ )	SSDAT++; // Add 1 for Read bit in AdrWord
      I2C_SET_AA;                   //wait on ACK bit
    break;

    //STATE 18h:   SLR+W was transmitted, ACK bit received 
    //ACTION:      Transmit data byte, ACK bit received
    //PREVIOUS STATE: 0x08 or 0x10                     
    case 0x18 :                     //master transmit, after sending
      I2C_nb_transmited=0;          //slave address, now load data
      SSDAT = *(I2C_message.buf);   //byte and send it              
      I2C_SET_AA;                   //wait on ACK bit
    break;

    //STATE 20h:   SLR+W was transmitted, NOT ACK bit received
    //ACTION:      Transmit STOP
    case 0x20 :
      I2C_SET_STOP;
      b_I2C_busy = FALSE;
      I2C_Err  = NoHostAdrAck;
    break;

  //STATE 28h:   DATA was transmitted, ACK bit received 
  //ACTION:      If last byte, send STOP, else send more data bytes 
  case 0x28 :             //master transmit, after sending
                          //data byte, ACK received
    I2C_nb_transmited++;                    // inc nb data transmit on message 
    I2C_message.buf++;                      // inc pointer ti data to be transmited
    if ( I2C_nb_transmited < I2C_message.nbbytes  ) //if there are still bytes to send
    {
      SSDAT = *(I2C_message.buf);
      I2C_SET_AA;                           //wait on ACK bit
    }
    else 
    {                    //run out of data, send stop,
      I2C_SET_STOP;
      I2C_Err  = Tranfer_OK;
      b_I2C_busy = FALSE;         //transfer complete, clear b_I2C_busy
    }
  break;

    //STATE 30h:   DATA was transmitted, NOT ACK bit received 
    //ACTION:      Transmit STOP     
    case 0x30 :
      I2C_SET_STOP;
      b_I2C_busy = FALSE;
      I2C_Err  = NoHostDataAck;
    break;

    //STATE 38h:   Arbitration lost in SLA+W or DATA.  
    //ACTION:      Release bus, enter not addressed SLV mode
    //             Wait for bus lines to be free 
    case 0x38 :
      b_I2C_busy = FALSE;
      I2C_Err  = ArbitrationLost;
      /*
      #ifdef USER_I2C_FCT_ARBITRATION_LOST_IN_SLA+W_OR_DATA
      I2C_fct_arb_lostinSLAorDATA();
      #endif
      */
    break;

    //MASTER RECEIVER MODE FOLLOWS 
    //STATE 40h:   SLA+R transmitted, ACK received 
    //ACTION:      Receive DATA, ACK to be returned 
    //PREVIOS STATE: 0x08 or 0x10
    case 0x40 :               //master receive, after sending
      if ( I2C_message.nbbytes == 1 )
      {
        I2C_CLEAR_AA;      // only one data to receive, noACK to be send after the fisrt incoming data
      }
      else
      {
        I2C_SET_AA;      //wait on ACK bit 
        I2C_nb_transmited=0;      //data byte to be received, NOT ACK bit to follow  --> 0x58    
      }
    break;
  
    //STATE 48h:   SLA+R transmitted, NOT ACK received 
    //ACTION:      Transmit STOP 
    case 0x48 :
      I2C_SET_STOP;
      b_I2C_busy = FALSE;
      I2C_Err  = NoHostAdrAck;
    break;

    //STATE 50h:  Data has been received, ACK returned 
    //ACTION:     Read DATA. If expecting more continue else STOP 
    case 0x50 :   //master receive, received data 
                  //byte and ACK, copy it into
      *(I2C_message.buf+I2C_nb_transmited) = SSDAT;      //buffer 
      I2C_nb_transmited++;
      if ( I2C_nb_transmited < I2C_message.nbbytes )
      {
        I2C_SET_AA;             //get more bytes 
      }
      else
      {
        I2C_CLEAR_AA;           //only one more byte to come 
      }
    break;

    //STATE 58h:   Data has been received, NOT ACK returned 
    //ACTION:      Read DATA. Generate STOP     
    case 0x58 :
      *(I2C_message.buf+I2C_nb_transmited) = SSDAT;
      I2C_SET_STOP;
      b_I2C_busy = FALSE;
      I2C_Err  = Tranfer_OK;
    break;

    //STATE 60h:   Own SLA+W has been received,ACK returned 
    //ACTION:      Read DATA. return ACK    
    case 0x60 :
      I2C_SET_AA;
      b_I2C_busy = TRUE;
      I2C_RecPtr=0;
    break;

    //STATE 68h:   Arbitration lost in SLA and R/W as MASTER. Own SLA 
    //             +W has been received. ACK returned   
    //ACTION:      Read DATA. return ACK
    //             re-start MASTER,
    case 0x68 :
      I2C_SET_START;
    break;

    //STATE 70h:   General call received, ACK returned
    //ACTION:      Receive DATA. return ACK
    case 0x70 :
      I2C_SET_AA;
      b_I2C_busy = TRUE;
    break;