Suche einfaches TWI Beispiel

Anbei eine einfache Polled-Mode Lösung für eine TWI-Master Anwendung. 
(Für TWI-Slave empfehle ich den ISR-Modus zu nutzen, da die SW nicht die 
Zeit  damit verbraten sollte, ständig auf ein TWI-Ereigniss warten zu 
müssen.

[c]
#include <avr/interrupt.h>
#include <util/twi.h>

//-------------------------------------------
// Definition of local constants
//-------------------------------------------

// master transfer acknowledge for address or data
#define TW_MT_ACK (u08)0x08

//-------------------------------------------
// Function Prototypes
//-------------------------------------------
void TWI_init(void);
void TWI_read (u08 TWI_adr, u08 *val, u08 count);
void TWI_write(u08 TWI_adr, u08 *val, u08 count);

//--------------------------------------------------------
// Intialize the I2C-Bus Interface
// as Master with SCL 100kHz, non interrupt driven
//--------------------------------------------------------

void TWI_init(void)
{
  //--------------------------------------------------------
  // SCL frequency: 102.400 kHz (F_CPU = 7.3728 MHz)
  // SCL = F_CPU/(16+2*TWBR*4^TWSR)
  //--------------------------------------------------------
  TWBR = 0x1C;                 // TWI-datrate divider = 28
  TWSR = 0x00;                 // TWI-clock prescaler = 1
  TWCR = (1<<TWEA)|(1<<TWEN);  // no interrupt mode
}



void TWI_read(u08 TWI_adr, u08 *val, u08 count)
//------------------------------------------------
// Read n=count bytes from I2C-Bus in polled mode
// needs about 200us for reading addr + one byte
//------------------------------------------------
{
  u08 i=0;
  TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);     // send START condition
  while (!(TWCR & (1<<TWINT)));               // wait for response
  if ((TWSR & 0xF8) == TW_START)              // if START was successful
  {
    TWDR = (TWI_adr | 0x01);                  // put slave address+READ 
to TWDR
    TWCR = (1<<TWINT)|(1<<TWEN);              // and start transmission
    while (!(TWCR & (1<<TWINT)));             // wait for response
    if ((TWSR & 0xF8) == TW_MR_SLA_ACK)       // if acknowledge ok
    {
      count--;
      while (count>i)                         // while more than one 
byte to read
      {
        TWCR=(1<<TWINT)|(1<<TWEA)|(1<<TWEN);  // then start transfer 
with acknowledge
        while (!(TWCR & (1<<TWINT)));         // wait for response
        val[i++]=TWDR;                        // read databyte from TWDR
      }
      TWCR=(1<<TWINT)|(1<<TWEN);              // start last byte 
transfer without acknowledge
      while (!(TWCR & (1<<TWINT)));           // wait for response
      val[i]=TWDR;                            // read databyte from TWDR
    }
    else
    {
      UART0_putl_I("Error: I2C[R] Addr");
    }
  }
  else
  {
    UART0_putl_I("Error: I2C[R] Start");
  }
  TWCR = (1<<TWINT)|(1<<TWSTO)|(1<<TWEN);      // transmit STOP 
condition
  delay_us(10);                                // wait until STOP is 
transmitted
}



void TWI_write(u08 TWI_adr, u08 *val, u08 count)
//------------------------------------------------
// write n=count bytes to I2C-Bus in polled mode
// needs about 200us for writing Addr + one byte
//------------------------------------------------
{
  TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);   // send START condition
  while (!(TWCR & (1<<TWINT)));             // wait for response
  if ((TWSR & 0xF8) == TW_START)            // if START was successful
  {
    TWDR = (TWI_adr & 0xFE);                // put slave address+WRITE 
to TWDR
    TWCR = (1<<TWINT)|(1<<TWEN);            // and start transmission
    for (u08 i=0; i<count; i++)
    {
      while (!(TWCR & (1<<TWINT)));         // wait for response
      if ((TWSR & 0xC8) == TW_MT_ACK)       // if acknowledge ok
      {
        TWDR = val[i];                      // put databyte  to TWDR
        TWCR = (1<<TWINT)|(1<<TWEN);        // and start transmission
      }
      else
      {
        UART0_putl_I("Error: I2C[W] Data");
      }
    }
  }
  else
  {
    UART0_putl_I("Error: I2C[W] Start");
  }
  while (!(TWCR & (1<<TWINT)));             // wait for response
  TWCR = (1<<TWINT)|(1<<TWSTO)|(1<<TWEN);   // transmit STOP condition
  delay_us(10);                             // wait until STOP is 
transmitted
}
[\c]