ATmega als I²C Master

(English version) Um am ATmega I²C als Master zum laufen zu kriegen war ein riesiger Kampf. Ich bin jedoch auf eine Version gekommen, die KEINE Probleme mit Compiler oder ähnlichem macht. Im Endeffekt habe ich Code aus einer fertigen Implementierung von Manfred Langemann benutzt, diese Implementierung einzubinden klappte bei mir leider nicht, daher habe ich den Code herauskopiert. Um also an einem ATmega I²C benutzen zu können muss man (wenn man es so wie ich macht) die folgenden Zeilen am Anfang des Programmes einfügen:

#define F_CPU 16000000

#define TRUE 1
#define FALSE 0

#include <avr/interrupt.h>

//#include "General.h"
//#include "TWI_Master.h"

/****************************************************************************
  TWI State codes
****************************************************************************/
// General TWI Master staus codes                     
#define TWI_START                    0x08  // START has been transmitted 
#define TWI_REP_START                0x10  // Repeated START has been transmitted
#define TWI_ARB_LOST                0x38  // Arbitration lost

// TWI Master Transmitter staus codes                     
#define TWI_MTX_ADR_ACK                0x18  // SLA+W has been tramsmitted and ACK received
#define TWI_MTX_ADR_NACK            0x20  // SLA+W has been tramsmitted and NACK received
#define TWI_MTX_DATA_ACK            0x28  // Data byte has been tramsmitted and ACK received
#define TWI_MTX_DATA_NACK            0x30  // Data byte has been tramsmitted and NACK received

// TWI Master Receiver staus codes 
#define TWI_MRX_ADR_ACK                0x40  // SLA+R has been tramsmitted and ACK received
#define TWI_MRX_ADR_NACK            0x48  // SLA+R has been tramsmitted and NACK received
#define TWI_MRX_DATA_ACK            0x50  // Data byte has been received and ACK tramsmitted
#define TWI_MRX_DATA_NACK            0x58  // Data byte has been received and NACK tramsmitted

// TWI Slave Transmitter staus codes
#define TWI_STX_ADR_ACK                0xA8  // Own SLA+R has been received; ACK has been returned
#define TWI_STX_ADR_ACK_M_ARB_LOST    0xB0  // Arbitration lost in SLA+R/W as Master; own SLA+R has been received; ACK has been returned
#define TWI_STX_DATA_ACK            0xB8  // Data byte in TWDR has been transmitted; ACK has been received
#define TWI_STX_DATA_NACK            0xC0  // Data byte in TWDR has been transmitted; NOT ACK has been received
#define TWI_STX_DATA_ACK_LAST_BYTE    0xC8  // Last data byte in TWDR has been transmitted (TWEA = “0”); ACK has been received

// TWI Slave Receiver staus codes
#define TWI_SRX_ADR_ACK                0x60  // Own SLA+W has been received ACK has been returned
#define TWI_SRX_ADR_ACK_M_ARB_LOST    0x68  // Arbitration lost in SLA+R/W as Master; own SLA+W has been received; ACK has been returned
#define TWI_SRX_GEN_ACK                0x70  // General call address has been received; ACK has been returned
#define TWI_SRX_GEN_ACK_M_ARB_LOST    0x78  // Arbitration lost in SLA+R/W as Master; General call address has been received; ACK has been returned
#define TWI_SRX_ADR_DATA_ACK        0x80  // Previously addressed with own SLA+W; data has been received; ACK has been returned
#define TWI_SRX_ADR_DATA_NACK        0x88  // Previously addressed with own SLA+W; data has been received; NOT ACK has been returned
#define TWI_SRX_GEN_DATA_ACK        0x90  // Previously addressed with general call; data has been received; ACK has been returned
#define TWI_SRX_GEN_DATA_NACK        0x98  // Previously addressed with general call; data has been received; NOT ACK has been returned
#define TWI_SRX_STOP_RESTART        0xA0  // A STOP condition or repeated START condition has been received while still addressed as Slave

// TWI Miscellaneous status codes
#define TWI_NO_STATE                0xF8  // No relevant state information available; TWINT = “0”
#define TWI_BUS_ERROR                0x00  // Bus error due to an illegal START or STOP condition

#define TWIM_READ    1
#define TWIM_WRITE   0

/*******************************************************
 Public Function: TWIM_Init

 Purpose: Initialise the TWI Master Interface

 Input Parameter:
     - uint16_t    TWI_Bitrate (Hz)

 Return Value: uint8_t
     - FALSE:    Bitrate too high
     - TRUE:        Bitrate OK

*******************************************************/
uint8_t TWIM_Init (uint32_t TWI_Bitrate)
    {
/*
** Set TWI bitrate
** If bitrate is too high, then error return
*/
    TWBR = ((F_CPU/TWI_Bitrate)-16)/2;
    if (TWBR < 11) return FALSE;

    return TRUE;
    }
/*******************************************************
 Public Function: TWIM_Start

 Purpose: Start the TWI Master Interface

 Input Parameter:
     - uint8_t    Device address
     - uint8_t    Type of required Operation:
                TWIM_READ: Read data from the slave
                TWIM_WRITE: Write data to the slave

 Return Value: uint8_t
      - TRUE:        OK, TWI Master accessible
     - FALSE:    Error in starting TWI Master

*******************************************************/
uint8_t TWIM_Start (uint8_t Address, uint8_t TWIM_Type)//1 = read, 0 = write
    {
    uint8_t        twst;
/*
** Send START condition
*/
    TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
/*
** Wait until transmission completed
*/
    while (!(TWCR & (1<<TWINT)));
/*
** Check value of TWI Status Register. Mask prescaler bits.
*/
    twst = TWSR & 0xF8;
    if ((twst != TWI_START) && (twst != TWI_REP_START)) return FALSE;
/*
** Send device address
*/
    TWDR = (Address<<1) + TWIM_Type;
    TWCR = (1<<TWINT)|(1<<TWEN);
/*
** Wait until transmission completed and ACK/NACK has been received
*/
    while (!(TWCR & (1<<TWINT)));
/*
** Check value of TWI Status Register. Mask prescaler bits.
*/
    twst = TWSR & 0xF8;
    if ((twst != TWI_MTX_ADR_ACK) && (twst != TWI_MRX_ADR_ACK)) return FALSE;

    return TRUE;
    }
/*******************************************************
 Public Function: TWIM_Stop

 Purpose: Stop the TWI Master

 Input Parameter: None

 Return Value: None

*******************************************************/
void TWIM_Stop (void)
    {
/*
** Send stop condition
*/
    TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);
/*
** Wait until stop condition is executed and bus released
*/
    while (TWCR & (1<<TWINT));
    }
/*******************************************************
 Public Function: TWIM_Write

 Purpose: Write a byte to the slave

 Input Parameter:
     - uint8_t    Byte to be sent

 Return Value: uint8_t
      - TRUE:        OK, Byte sent
     - FALSE:    Error in byte transmission

*******************************************************/
uint8_t TWIM_Write (uint8_t byte)
    {
    uint8_t   twst;
/*
** Send data to the previously addressed device
*/
    TWDR = byte;
    TWCR = (1<<TWINT)|(1<<TWEN);
/*
** Wait until transmission completed
*/
    while (!(TWCR & (1<<TWINT)));
/*
** Check value of TWI Status Register. Mask prescaler bits
*/
    twst = TWSR & 0xF8;
    if (twst != TWI_MTX_DATA_ACK) return 1;

    return 0;
    }
/*******************************************************
 Public Function: TWIM_ReadAck

 Purpose: Read a byte from the slave and request next byte

 Input Parameter: None

 Return Value: uint8_t
      - uint8_t    Read byte

*******************************************************/
uint8_t TWIM_ReadAck (void)
    {
    TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWEA);
    while (!(TWCR & (1<<TWINT)));   

    return TWDR;
    }
/*******************************************************
 Public Function: TWIM_ReadAck

 Purpose: Read the last byte from the slave

 Input Parameter: None

 Return Value: uint8_t
      - uint8_t    Read byte

*******************************************************/
uint8_t TWIM_ReadNack (void)
    {
    TWCR = (1<<TWINT)|(1<<TWEN);
    while(!(TWCR & (1<<TWINT)));
   
    return TWDR;
    }