twi.c

Atmel的AT91SAM7X256的和24系列EEPROM通讯的源程序

/* ----------------------------------------------------------------------------
 *         ATMEL Microcontroller Software Support  -  ROUSSET  -
 * ----------------------------------------------------------------------------
 * Copyright (c) 2007, Atmel Corporation

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#ifndef trace_LEVEL
    #define trace_LEVEL  1
#endif

//------------------------------------------------------------------------------
//         Headers
//------------------------------------------------------------------------------

#include "twi.h"
#include <utility/math.h>
#include <utility/assert.h>
#include <utility/trace.h>

//------------------------------------------------------------------------------
//         Global functions
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
/// Configures a TWI peripheral to operate in master mode, at the given
/// frequency (in Hz). The duty cycle of the TWI clock is set to 50%.
/// \param pTwi  Pointer to an AT91S_TWI instance.
/// \param twck  Desired TWI clock frequency.
/// \param mck  Master clock frequency.
//------------------------------------------------------------------------------
void TWI_Configure(AT91S_TWI *pTwi, unsigned int twck, unsigned int mck)
{
    unsigned int ckdiv = 0;
    unsigned int cldiv;
    unsigned char ok = 0;

    trace_LOG(trace_DEBUG, "-D- TWI_Configure()\n\r");
    SANITY_CHECK(pTwi);

    // Reset the TWI
    pTwi->TWI_CR = AT91C_TWI_SWRST;

    // Set master mode
    pTwi->TWI_CR = AT91C_TWI_MSEN;

    // Configure clock
    while (!ok) {
        
        cldiv = ((mck / (2 * twck)) - 3) / power(2, ckdiv);
        if (cldiv <= 255) {

            ok = 1;
        }
        else {

            ckdiv++;
        }
    }

    ASSERT(ckdiv < 8, "-F- Cannot find valid TWI clock parameters\n\r");
    trace_LOG(trace_INFO, "-D- Using CKDIV = %d and CLDIV/CHDIV = %d\n\r", ckdiv, cldiv);
    pTwi->TWI_CWGR = (ckdiv << 16) | (cldiv << 8) | cldiv;
}

//------------------------------------------------------------------------------
/// Sends a STOP condition on the TWI.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//------------------------------------------------------------------------------
void TWI_Stop(AT91S_TWI *pTwi)
{
    SANITY_CHECK(pTwi);

    pTwi->TWI_CR = AT91C_TWI_STOP;
}

//------------------------------------------------------------------------------
/// Starts a read operation on the TWI bus with the specified slave, and returns
/// immediately. Data must then be read using TWI_ReadByte() whenever a byte is
/// available (poll using TWI_ByteReceived()).
/// \param pTwi  Pointer to an AT91S_TWI instance.
/// \param address  Slave address on the bus.
/// \param iaddress  Optional internal address bytes.
/// \param isize  Number of internal address bytes.
//-----------------------------------------------------------------------------
void TWI_StartRead(
    AT91S_TWI *pTwi,
    unsigned char address,
    unsigned int iaddress,
    unsigned char isize)
{
    trace_LOG(trace_DEBUG, "-D- TWI_StartRead()\n\r");
    SANITY_CHECK(pTwi);
    SANITY_CHECK((address & 0x80) == 0);
    SANITY_CHECK((iaddress & 0xFF000000) == 0);
    SANITY_CHECK(isize < 4);

    // Set slave address and number of internal address bytes
    pTwi->TWI_MMR = (isize << 8) | AT91C_TWI_MREAD | (address << 16);

    // Set internal address bytes
    pTwi->TWI_IADR = iaddress;

    // Send START condition
    pTwi->TWI_CR = AT91C_TWI_START;
}

//-----------------------------------------------------------------------------
/// Reads a byte from the TWI bus. The read operation must have been started
/// using TWI_StartRead() and a byte must be available (check with
/// TWI_ByteReceived()).
/// Returns the byte read.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//-----------------------------------------------------------------------------
unsigned char TWI_ReadByte(AT91S_TWI *pTwi)
{
    SANITY_CHECK(pTwi);

    return pTwi->TWI_RHR;
}

//-----------------------------------------------------------------------------
/// Sends a byte of data to one of the TWI slaves on the bus. This function
/// must be called once before TWI_StartWrite() with the first byte of data
/// to send, then it shall be called repeatedly after that to send the
/// remaining bytes.
/// \param pTwi  Pointer to an AT91S_TWI instance.
/// \param byte  Byte to send.
//-----------------------------------------------------------------------------
void TWI_WriteByte(AT91S_TWI *pTwi, unsigned char byte)
{
    SANITY_CHECK(pTwi);

    pTwi->TWI_THR = byte;
}

//-----------------------------------------------------------------------------
/// Starts a write operation on the TWI to access the selected slave, then
/// returns immediately. A byte of data must be provided to start the write;
/// other bytes are written next.
/// \param pTwi  Pointer to an AT91S_TWI instance.
/// \param address  Address of slave to acccess on the bus.
/// \param iaddress  Optional slave internal address.
/// \param isize  Number of internal address bytes.
/// \param byte  First byte to send.
//-----------------------------------------------------------------------------
void TWI_StartWrite(
    AT91S_TWI *pTwi,
    unsigned char address,
    unsigned int iaddress,
    unsigned char isize,
    unsigned char byte)
{
    trace_LOG(trace_DEBUG, "-D- TWI_StartWrite()\n\r");
    SANITY_CHECK(pTwi);
    SANITY_CHECK((address & 0x80) == 0);
    SANITY_CHECK((iaddress & 0xFF000000) == 0);
    SANITY_CHECK(isize < 4);

    // Set slave address and number of internal address bytes
    pTwi->TWI_MMR = (isize << 8) | (address << 16);

    // Set internal address bytes
    pTwi->TWI_IADR = iaddress;

    // Write first byte to send
    TWI_WriteByte(pTwi, byte);
}

//-----------------------------------------------------------------------------
/// Returns 1 if a byte has been received and can be read on the given TWI
/// peripheral; otherwise, returns 0. This function resets the status register
/// of the TWI.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//-----------------------------------------------------------------------------
unsigned char TWI_ByteReceived(AT91S_TWI *pTwi)
{
    return ((pTwi->TWI_SR & AT91C_TWI_RXRDY) == AT91C_TWI_RXRDY);
}

//-----------------------------------------------------------------------------
/// Returns 1 if a byte has been sent, so another one can be stored for
/// transmission; otherwise returns 0. This function clears the status register
/// of the TWI.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//-----------------------------------------------------------------------------
unsigned char TWI_ByteSent(AT91S_TWI *pTwi)
{
    return ((pTwi->TWI_SR & AT91C_TWI_TXRDY) == AT91C_TWI_TXRDY);
}

//-----------------------------------------------------------------------------
/// Returns 1 if the current transmission is complete (the STOP has been sent);
/// otherwise returns 0.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//-----------------------------------------------------------------------------
unsigned char TWI_TransferComplete(AT91S_TWI *pTwi)
{
    return ((pTwi->TWI_SR & AT91C_TWI_TXCOMP) == AT91C_TWI_TXCOMP);
}

//-----------------------------------------------------------------------------
/// Enables the selected interrupts sources on a TWI peripheral.
/// \param pTwi  Pointer to an AT91S_TWI instance.
/// \param sources  Bitwise OR of selected interrupt sources.
//-----------------------------------------------------------------------------
void TWI_EnableIt(AT91S_TWI *pTwi, unsigned int sources)
{
    SANITY_CHECK(pTwi);
    SANITY_CHECK((sources & 0xFFFFFEF8) == 0);

    pTwi->TWI_IER = sources;
}

//-----------------------------------------------------------------------------
/// Disables the selected interrupts sources on a TWI peripheral.
/// \param pTwi  Pointer to an AT91S_TWI instance.
/// \param sources  Bitwise OR of selected interrupt sources.
//-----------------------------------------------------------------------------
void TWI_DisableIt(AT91S_TWI *pTwi, unsigned int sources)
{
    SANITY_CHECK(pTwi);
    SANITY_CHECK((sources & 0xFFFFFEF8) == 0);

    pTwi->TWI_IDR = sources;
}

//-----------------------------------------------------------------------------
/// Returns the current status register of the given TWI peripheral. This
/// resets the internal value of the status register, so further read may yield
/// different values.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//-----------------------------------------------------------------------------
unsigned int TWI_GetStatus(AT91S_TWI *pTwi)
{
    SANITY_CHECK(pTwi);

    return pTwi->TWI_SR;
}

//-----------------------------------------------------------------------------
/// Returns the current status register of the given TWI peripheral, but
/// masking interrupt sources which are not currently enabled.
/// This resets the internal value of the status register, so further read may
/// yield different values.
/// \param pTwi  Pointer to an AT91S_TWI instance.
//-----------------------------------------------------------------------------
unsigned int TWI_GetMaskedStatus(AT91S_TWI *pTwi)
{
    SANITY_CHECK(pTwi);

    return (pTwi->TWI_SR & pTwi->TWI_IMR);
}