发表于
2008-3-19 20:00:29
#include "C8051F310.H"
#include "common.h"
#include "i2c.h"
/* Ports */
sbit SCL = P0 ^ 7;
sbit SDA = P0 ^ 6;
sbit CHECK = P1 ^ 0;
/* ------------ DEFINES --------------- */
/* I2c read/write flags */
#define I2C_WRITE_FLAG 0x00 /* bit 0 of slave-addres byte */
#define I2C_READ_FLAG 0x01
/* bus logic levels */
#define LO 0
#define HI 1
/* Delay constants */
#define _5US 8
/* Retry times on NACK */
#define NACK_RETRY_MAX 5
/* ------------ LOCAL DATA ------------ */
xdata UINT8 I2cStatus;
xdata UINT8 RxBit;
xdata UINT8 RxByte;
/* ---------- MODULE FUNCTIONS ------- */
void Delay ( UINT8 Time );
UINT8 SetScl( UINT8 State );
UINT8 SetSda( UINT8 State );
void FloatSda( void );
UINT8 I2cStart();
UINT8 I2cStop();
UINT8 I2cTxBit( UINT8 BitVal );
UINT8 I2cRxBit( void );
UINT8 I2cTxByte( UINT8 TxData);
UINT8 I2cRxByte( UINT8 AckState );
/*---------------- Function Header -------------------------------------------
FUNCTION InitI2c
PURPOSE Initialises I2c driver
INPUT None
OUTPUT I2c status byte indicating the idle-state of the bus
----------------------------------------------------------------------------*/
UINT8 InitI2c ( void )
{
/* configure C8051F310 ports for I2C operation:
SDA is connected to Port0, bit6
SCL is connected to Port0, bit7
both pins function in open-drain mode
*/
P0SKIP = 0xc0;
P0MDOUT &= ~0x30; /* set SDA and SCL = open-drain */
I2cStatus = 0; /* initialise driver status */
/* set initial idle state for bus (SDA and SCL = 1) */
return ( SetSda( HI ) || SetScl( HI ) );
}
/*---------------- Function Header -------------------------------------------
FUNCTION Delay
PURPOSE Programme delay in the microsecond range -
Called to meet I2C bus timing requirements
----------------------------------------------------------------------------*/
void Delay ( UINT8 Time )
{
UINT8 i;
EA = 0; /* interrupts disabled during delay */
for (i = 0; i < Time; i++);
EA = 1;
}
/*---------------- Function Header -------------------------------------------
FUNCTION SetScl
PURPOSE Sets I2C SCL line to the required level. Because the bus is a
wire-OR configuration, it may take some time to establish a
logic '1' due to slow risetime, clock stretching etc.
An arbitrary timeout of 250us is allowed.
INPUT Required bus state
OUTPUT Flag indicating result: 1 = OK, 0 = bus line stuck.
MODIFIES I2cStatus
----------------------------------------------------------------------------*/
UINT8 SetScl( UINT8 State )
{
// UINT16 Timeout = 450; /* approx 250us */
UINT16 Timeout = 10000; /* approx 250us */
SCL = State;
while ( (SCL != State) && --Timeout);
if ( Timeout )
return true;
else
{
I2cStatus |= I2C_ERROR_SCL_STUCK;
return false;
}
}
/*---------------- Function Header -------------------------------------------
FUNCTION SetSda
PURPOSE Sets I2C SDA line to the required level. Because the bus is a
wire-OR configuration, it may take some time to establish a
logic '1' due to slow risetime, clock stretching etc.
An arbitrary timeout of 250us is allowed.
INPUT Required bus state
OUTPUT Flag indicating result: 1 = OK, 0 = bus line stuck.
MODIFIES I2cStatus
----------------------------------------------------------------------------*/
UINT8 SetSda( UINT8 State )
{
// UINT16 Timeout = 450; /* approx 250us */
UINT16 Timeout = 10000; /* approx 250us */
SDA = State;
while ( (SDA != State) && --Timeout);
if ( Timeout )
return true;
else
{
I2cStatus |= I2C_ERROR_SDA_STUCK;
return false;
}
}
/*---------------- Function Header -------------------------------------------
FUNCTION FloatSda
PURPOSE Sets I2C SDA line to 'input mode'.
Note: this function does not check the line is high because
a slave may be legitimately driving SDA low.
----------------------------------------------------------------------------*/
void FloatSda( void )
{
SDA = HI;
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cStart
PURPOSE Applies an appropriately timed START condition to the I2c bus.
OUTPUT Flag indicating result: 1 = OK, 0 = bus line stuck.
MODIFIES I2cStatus
----------------------------------------------------------------------------*/
UINT8 I2cStart()
{
if ( !SDA ) /* ensure SDA is high */
{
if ( !SetSda(HI) )
return false;
}
if ( !SCL ) /* ensure SCL is high */
{
if ( !SetScl(HI) )
return false;
}
Delay( _5US ); /* Philips tSU:STA > 4.7us */
SetSda(LO);
Delay( _5US ); /* Philips tHD:SDA > 4us */
return ( SetScl(LO) );
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cStop
PURPOSE Applies an appropriately timed STOP condition to the I2c bus.
OUTPUT Flag indicating result: 1 = OK, 0 = bus line stuck.
MODIFIES I2cStatus
----------------------------------------------------------------------------*/
UINT8 I2cStop()
{
SetSda(LO); /* ensure SDA is low */
if ( !SetScl(HI) )
return false;
Delay( _5US ); /* Philips tSU:STO > 4us */
return ( SetSda(HI) );
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cTxBit
PURPOSE Drives the specified data bit to the I2c bus.
OUTPUT Flag indicating result: 1 = OK, 0 = bus line stuck.
MODIFIES I2cStatus
----------------------------------------------------------------------------*/
UINT8 I2cTxBit( UINT8 BitVal )
{
if ( !SetSda(BitVal) )
return false;
Delay( _5US ); /* Philips tLOW > 4.7us */
if ( !SetScl(HI) )
return false;
Delay( _5US ); /* Philips tHIGH > 4us */
return ( SetScl(LO) );
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cRxBit
PURPOSE Receives a data bit from the I2c bus.
OUTPUT Flag indicating result: 1 = OK, 0 = bus line stuck.
Data bit is saved to RxBit
MODIFIES I2cStatus
----------------------------------------------------------------------------*/
UINT8 I2cRxBit( void )
{
FloatSda(); /* float SDA - can't check state as slave maybe driving SDA */
Delay( _5US ); /* Philips tLOW > 4.7us */
if ( !SetScl(HI) )
return false;
Delay( _5US ); /* Philips tHIGH > 4us */
RxBit = SDA;
return ( SetScl(LO) );
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cTxByte
PURPOSE Sequences transmission of a data byte to the I2c bus.
OUTPUT Flag indicating result: 1 = slave acknowledged, 0 = no ack/fail.
Data bit is saved to RxBit
MODIFIES I2cStatus: State of ACK bit and error flags
----------------------------------------------------------------------------*/
UINT8 I2cTxByte( UINT8 TxData)
{
UINT8 i;
UINT8 t = TxData;
for (i= 0;i < 8;i++)
{
if ( !I2cTxBit( (t & 0x80) ? 1 : 0 ) )
return false;
t <<= 1;
}
if ( I2cRxBit() )
{
if (RxBit)
I2cStatus |= I2C_ERROR_NO_ACK;
return ( !RxBit ); /* returns '1' if ACK recieved */
}
else
return false;
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cTxByte
PURPOSE Sequences reception of a data byte from the I2c bus.
INPUT Flag indicating state of ACK bit to be sent to the slave
OUTPUT Flag indicating result: 1 = OK, 0 = fail.
Data byte is saved to RxByte
MODIFIES I2cStatus: State of error flags
----------------------------------------------------------------------------*/
UINT8 I2cRxByte( UINT8 AckState )
{
UINT8 i;
UINT8 r = 0;
for (i= 0;i < 8;i++)
{
if ( !I2cRxBit() )
return false;
r <<= 1;
r |= RxBit;
}
RxByte = r;
return ( I2cTxBit ( AckState ) );
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cWrite
PURPOSE Sequences a write-cycle to a slave device on the I2c bus.
send START
send slave-adddress + write flag (check ACK)
send write pointer (check ACK)
read data bytes (with NACK at last byte) (check all ACKs)
INPUT I2cAddress: specifies slave device 7-bit address
DeviceAddress: specifies address pointer within the device
Data: Pointer to write-data (byte) array
ByteCount: specifies number of bytes to write
OUTPUT I2cStatus byte indicating result of I2c cycle.
MODIFIES I2cStatus: all flags
----------------------------------------------------------------------------*/
UINT8 I2cWrite( UINT8 I2cAddress, UINT8 DeviceAddress, UINT8 *Data, UINT8 ByteCount)
{
UINT8 i;
UINT8 *WriteDataPtr;
CHECK = 1;
i = 0;
do { /* attempt to address device up to NACK_RETRY_MAX times */
I2cStatus = 0;
if ( I2cStart() )
{
if ( !I2cTxByte( (I2cAddress * 2) + I2C_WRITE_FLAG ) )
I2cStop();
}
} while ( (I2cStatus != 0) && (++i < NACK_RETRY_MAX) );
CHECK = 0;
if ( i >= NACK_RETRY_MAX )
return I2cStatus;
if ( !I2cTxByte( DeviceAddress ) )
{
I2cStop();
return I2cStatus;
}
WriteDataPtr = Data;
for ( i = 0; i < ByteCount; i++)
{
if ( !I2cTxByte( *WriteDataPtr++ ) )
{
I2cStop();
return I2cStatus;
}
}
I2cStop();
return I2cStatus;
}
/*---------------- Function Header -------------------------------------------
FUNCTION I2cRead
PURPOSE Sequences a read-cycle to a slave device on the I2c bus:
send START
send slave-adddress + write flag (check ACK)
send read pointer (check ACK)
send re-START
send slave-adddress + read flag (check ACK)
read data bytes (with NACK at last byte)
INPUT I2cAddress: specifies slave device 7-bit address
DeviceAddress: specifies address pointer within the device
Data: Pointer to return-data (byte) array
ByteCount: specifies number of bytes to read
OUTPUT I2cStatus byte indicating result of I2c cycle.
MODIFIES I2cStatus: all flags
----------------------------------------------------------------------------*/
UINT8 I2cRead( UINT8 I2cAddress, UINT8 DeviceAddress, UINT8 *Data, UINT8 ByteCount)
{
UINT8 i;
UINT8 *ReadDataPtr;
i = 0;
do { /* attempt to address device up to NACK_RETRY_MAX times */
I2cStatus = 0;
if ( I2cStart() )
{
if ( !I2cTxByte( (I2cAddress * 2) + I2C_WRITE_FLAG ) )
I2cStop();
}
} while ( (I2cStatus != 0) && (++i < NACK_RETRY_MAX) );
if ( i >= NACK_RETRY_MAX )
return I2cStatus;
if ( !I2cTxByte( DeviceAddress ) )
{
I2cStop();
return I2cStatus;
}
i = 0;
do { /* attempt to address device up to NACK_RETRY_MAX times */
I2cStatus = 0;
if ( I2cStart() )
{
if ( !I2cTxByte( (I2cAddress * 2) + I2C_READ_FLAG ) )
I2cStop();
}
} while ( (I2cStatus != 0) && (++i < NACK_RETRY_MAX) );
if ( i >= NACK_RETRY_MAX )
return I2cStatus;
ReadDataPtr = Data;
for ( i = 0; i < ByteCount; i++)
{
if ( I2cRxByte( (i == (ByteCount - 1) ? 1 : 0 ) ) )
*ReadDataPtr++ = RxByte;
else
{
I2cStop();
return I2cStatus;
}
}
I2cStop();
return I2cStatus;
}