main.c

达拉斯 1-Wire 主机通信 这份资料展示了如何把 1-Wire 主机通信在应用到一个AVR系统中

// This file has been prepared for Doxygen automatic documentation generation.
/*! \file ********************************************************************
*
* Atmel Corporation
*
* \li File:               main.c
* \li Compiler:           IAR EWAAVR 3.20a
* \li Support mail:       [e-mail]
*
* \li Supported devices:  All AVRs with UART or USART module. 
*
* \li Application Note:   AVR318 - Dallas 1-Wire(R) master.
*                         
*
* \li Description:        Example on how to use the interrupt-driven 
*                         UART implementation of the 1-Wire(R) protocol.
*
*                         $Revision: 1.7 $
*                         $Date: Thursday, August 19, 2004 14:27:16 UTC $
****************************************************************************/

#include <ioavr.h>
#include <inavr.h>

#include "OWIIntFunctions.h"
#include "OWIInterruptDriven.h"
#include "..\common_files\OWIcrc.h"

void OWI_StateMachine();

// Defines used only in code example.
#define OWI_STATE_IDLE                  0
#define OWI_STATE_DETECT_PRESENCE1      1
#define OWI_STATE_WAIT_FOR_CONVERSION1  2
#define OWI_STATE_WAIT_FOR_CONVERSION2  3
#define OWI_STATE_DETECT_PRESENCE2      4
#define OWI_STATE_READ_SCRATCHPAD       5
#define OWI_STATE_CHECK_CRC             6

#define FALSE       0
#define TRUE        1

#define DS1820_START_CONVERSION         0x44    //!< DS1820 start conversion command
#define DS1820_READ_SCRATCHPAD          0xbe    //!< DS1820 Read scratchpad command

extern OWIflags OWIStatus;
extern unsigned char *OWIDataBuffer;

signed int temperature;


/*! \brief  Code example for the interrupt-driven driver.
 *
 *  This code example assumes that there is a DS1820 temperature sensor
 *  connected to the 1-Wire bus. The temperature sensor is continously 
 *  polled, and the temperature reading is output to PORTB.
 */
void main(void)
{  
    
    OWI_Init();    
    
    __enable_interrupt();
    
    // Configure PORTB as output. This can be used to output debugging values
    // to the LEDs on the STK500 development board.
    DDRB = 0xff;
    
    for(;;)
    {
        // If the 1-Wire(R) bus is not busy, run the state machine.
        if (!OWIStatus.busy)
        {
            OWI_StateMachine();    
        }        

        // Do something else while 1-Wire(R) bus is busy.
        PORTB = ~(temperature >> 1);
    }
}


/*! \brief  The state machine that controls communication on the 1-Wire bus
 *  
 *  This function is called from main every time the 1-Wire driver is not
 *  busy. The state machine will read the temperature from a DS1820 temperature
 *  sensor, crc check it, and put it in the global variable temperature if 
 *  everything is OK.
 */
void OWI_StateMachine()
{
    static unsigned char state = OWI_STATE_IDLE;
    static unsigned char buf[9];
    unsigned char i;
    unsigned char crc;
    
    // If an error has occurred since last time, clear all flags and
    // return to idle state.
    if (OWIStatus.error)
    {
        state = OWI_STATE_IDLE;
        OWIStatus.allFlags = FALSE;
    }
    
    switch (state)
    {
        case OWI_STATE_IDLE:
        {
            // Send reset signal and update state.
            OWI_DetectPresence();
            state = OWI_STATE_DETECT_PRESENCE1;
            break;
        }

        case OWI_STATE_DETECT_PRESENCE1:
        {
            // If no presence was detected, go back to idle state.
            if(OWIStatus.presenceDetected == FALSE)
            {
                state = OWI_STATE_IDLE;
            }
            // If presence was detected, send Skip ROM and Start conversion
            // signals. 
            else
            {
                buf[0] = OWI_ROM_SKIP;
                buf[1] = DS1820_START_CONVERSION;
                OWI_TransmitData(buf, 16);
                state = OWI_STATE_WAIT_FOR_CONVERSION1;
            }
            break;
        }

        case OWI_STATE_WAIT_FOR_CONVERSION1:
        {
            // Receive one byte of data to check for completion of the 
            // temperature conversion.
            OWI_ReceiveData(buf, 8);
            state = OWI_STATE_WAIT_FOR_CONVERSION2;
            break;
        }
    
        case OWI_STATE_WAIT_FOR_CONVERSION2:
        {
            // If everything received was zero. Jump to the last state
            // to receive a new byte.
            if (buf[0] == 0x00)
            {
                state = OWI_STATE_WAIT_FOR_CONVERSION1;
            }
            // If there was at least 1 one received, continue with a new
            // reset.
            else
            {
                OWI_DetectPresence();
                state = OWI_STATE_DETECT_PRESENCE2;
            }
            break;
        }
    
        case OWI_STATE_DETECT_PRESENCE2:
        {
            // If no presence was detected, go back to idle state.
            if(OWIStatus.presenceDetected == FALSE)
            {
                state = OWI_STATE_IDLE;
            }
            // If presence was detected, send Skip ROM and Read scratchpad
            // signals. 
            else
            {
                buf[0] = OWI_ROM_SKIP;
                buf[1] = DS1820_READ_SCRATCHPAD;
                OWI_TransmitData(buf, 16);
                state = OWI_STATE_READ_SCRATCHPAD;   
            }
            break;
        }
    
        case OWI_STATE_READ_SCRATCHPAD:
        {
            // Read the 9 bytes of scratchpad data.
            OWI_ReceiveData(buf, 9 * 8);
            state = OWI_STATE_CHECK_CRC;
            break;
        }
    
        case OWI_STATE_CHECK_CRC:
        {
            // Compare the computed crc with the crc read from the 
            // scratchpad. 
            crc = 0;
            for(i = 0; i < 8; i++)
            {
                crc =  OWI_ComputeCRC8(buf[i], crc);
            }
            // If they match, update the temperature variable.
            if (crc == buf[8])
            {
                temperature = buf[0] | (buf[1] << 8);                
                state = OWI_STATE_IDLE;
            }
            // If they don't match, go back to the second Reset to 
            // read the scratchpad again.
            else
            {
                OWI_DetectPresence();
                state = OWI_STATE_DETECT_PRESENCE2;
            }
            break;
        }
    }
}