twi.c

AVR的I2C驱动程序

#include "twi.h"
#include <avr/io.h>
#include <avr/interrupt.h>

volatile struct TWI_master_data *TWI_task_first = 0;
volatile struct TWI_master_data *TWI_task_last = 0;
volatile struct TWI_master_data *TWI_task_current = 0;
volatile struct TWI_slave_data *TWI_slave_send = 0;
volatile struct TWI_slave_data *TWI_slave_receive = 0;

void TWI_initialize()
{
  TWDR = 0xFF;
  TWSR = 0;
  TWCR = (1 << TWEN) |  (1 << TWIE) | (0 << TWINT) |
    (0 << TWEA) | (0 << TWSTA) | (0 << TWSTO) | (0 << TWWC);
  sei ();
}

void TWI_master_initialize (unsigned scl_frequency)
{
  TWBR = TWI_clock_frequency / (2 * scl_frequency) - 8;
} 

void
TWI_slave_initialize (unsigned char own_address,
		      struct TWI_slave_data *send,
		      struct TWI_slave_data *receive)
{
  TWAR = own_address;
  TWI_slave_send = send;
  TWI_slave_receive = receive;
  TWCR |= (1 << TWEA) | (0 << TWIE);
} 

void TWI_master (struct TWI_master_data *data)
{
  if (TWI_task_first == 0)
  {
    TWI_task_first = TWI_task_last = TWI_task_current =
      data;
    TWCR |= (1 << TWSTA) | (1 << TWINT);
  }
  else
  {
    TWI_task_last->next = data;
    TWI_task_last = data;
  }
}


/* General TWI Master staus codes */
#define TWI_START                  0x08
#define TWI_REP_START              0x10
#define TWI_ARB_LOST               0x38
/* TWI Master Transmitter staus codes */
#define TWI_MTX_ADR_ACK            0x18
#define TWI_MTX_ADR_NACK           0x20
#define TWI_MTX_DATA_ACK           0x28
#define TWI_MTX_DATA_NACK          0x30
/* TWI Master Receiver staus codes */
#define TWI_MRX_ADR_ACK            0x40
#define TWI_MRX_ADR_NACK           0x48
#define TWI_MRX_DATA_ACK           0x50
#define TWI_MRX_DATA_NACK          0x58
/* TWI Slave Transmitter staus codes */
#define TWI_STX_ADR_ACK            0xA8
#define TWI_STX_ADR_ACK_M_ARB_LOST 0xB0
#define TWI_STX_DATA_ACK           0xB8
#define TWI_STX_DATA_NACK          0xC0
#define TWI_STX_DATA_ACK_LAST_BYTE 0xC8
/* TWI Slave Receiver staus codes */
#define TWI_SRX_ADR_ACK            0x60
#define TWI_SRX_ADR_ACK_M_ARB_LOST 0x68
#define TWI_SRX_GEN_ACK            0x70
#define TWI_SRX_GEN_ACK_M_ARB_LOST 0x78
#define TWI_SRX_ADR_DATA_ACK       0x80
#define TWI_SRX_ADR_DATA_NACK      0x88
#define TWI_SRX_GEN_DATA_ACK       0x90
#define TWI_SRX_GEN_DATA_NACK      0x98
#define TWI_SRX_STOP_RESTART       0xA0
/* TWI Miscellaneous status codes */
#define TWI_NO_STATE               0xF8
#define TWI_BUS_ERROR              0x00

ISR (TWI_vect)
{

  static unsigned char string_index;
  switch (TWSR)
  {
  case TWI_START:
  case TWI_REP_START:
    string_index = 0;
  case TWI_MTX_ADR_ACK:
  case TWI_MTX_DATA_ACK:
    if (string_index < TWI_task_current->length)
    {
      TWDR = TWI_task_current->string[string_index++];
      TWCR = (1 << TWEN) |
	(1 << TWIE) | (1 << TWINT) |
	(0 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
	(0 << TWWC);
    }
    else
    {
      *TWI_task_current->flag = 0;
      if (TWI_task_current != TWI_task_last)
      {
	TWI_task_current = TWI_task_current->next;
	TWCR = (1 << TWEN) |
	  (1 << TWIE) | (1 << TWINT) |
	  (0 << TWEA) | (1 << TWSTA) | (0 << TWSTO) |
	  (0 << TWWC);
      }
      else
      {
	TWI_task_first = TWI_task_last = TWI_task_current =
	  0;
	TWCR =
	  (1 << TWEN) | (1 << TWIE) | (1 << TWINT) | (1 <<
						      TWEA)
	  | (0 << TWSTA) | (1 << TWSTO) | (0 << TWWC);
      }
    }
    break;
  case TWI_MRX_DATA_ACK:
    TWI_task_current->string[string_index++] = TWDR;
  case TWI_MRX_ADR_ACK:
    if (string_index < (TWI_task_current->length - 1))
    {
      TWCR = (1 << TWEN) |
	(1 << TWIE) | (1 << TWINT) |
	(1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
	(0 << TWWC);
    }
    else
    {
      TWCR = (1 << TWEN) |
	(1 << TWIE) | (1 << TWINT) |
	(0 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
	(0 << TWWC);
    }
    break;
  case TWI_MRX_DATA_NACK:
    TWI_task_current->string[string_index] = TWDR;
    *TWI_task_current->flag = 0;
    if (TWI_task_current != TWI_task_last)
    {
      TWI_task_current = TWI_task_current->next;
      TWCR = (1 << TWEN) |
	(1 << TWIE) | (1 << TWINT) |
	(0 << TWEA) | (1 << TWSTA) | (0 << TWSTO) |
	(0 << TWWC);
    }
    else
    {
      TWI_task_first = TWI_task_last = TWI_task_current = 0;
      TWCR =
	(1 << TWEN) | (1 << TWIE) | (1 << TWINT) | (1 <<
						    TWEA)
	| (0 << TWSTA) | (1 << TWSTO) | (0 << TWWC);
    }
    break;
  case TWI_ARB_LOST:
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (1 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  case TWI_MTX_ADR_NACK:
  case TWI_MRX_ADR_NACK:
  case TWI_MTX_DATA_NACK:
    TWI_task_first = TWI_task_current;
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (1 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  case TWI_STX_ADR_ACK:
    string_index = 0;
    *TWI_slave_send->flag = 0xFF;
  case TWI_STX_DATA_ACK:
    if (string_index < TWI_slave_send->length)
      TWDR = TWI_slave_send->string[string_index++];

    else
      TWDR = 0;
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  case TWI_STX_DATA_NACK:
    *TWI_slave_send->flag = 0;
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  case TWI_SRX_GEN_ACK:
  case TWI_SRX_ADR_ACK:
    string_index = 0;
    *TWI_slave_receive->flag = 0xFF;
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  case TWI_SRX_ADR_DATA_ACK:
  case TWI_SRX_GEN_DATA_ACK:
    if (string_index < TWI_slave_receive->length)
      TWI_slave_receive->string[string_index++] = TWDR;
    if (string_index == TWI_slave_receive->length)
      *TWI_slave_receive->flag = 0;
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  case TWI_SRX_STOP_RESTART:
    *TWI_slave_receive->flag = 0;
    TWI_slave_receive = TWI_slave_receive->next;
    if (TWI_task_current == 0)
      TWCR = (1 << TWEN) |
	(1 << TWIE) | (1 << TWINT) |
	(1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
	(0 << TWWC);

    else
      TWCR = (1 << TWEN) |
	(1 << TWIE) | (1 << TWINT) |
	(1 << TWEA) | (1 << TWSTA) | (0 << TWSTO) |
	(0 << TWWC);
    break;
  case TWI_SRX_ADR_DATA_NACK:
  case TWI_SRX_GEN_DATA_NACK:
  case TWI_STX_DATA_ACK_LAST_BYTE:
  case TWI_BUS_ERROR:
  default:
    TWCR = (1 << TWEN) |
      (1 << TWIE) | (1 << TWINT) |
      (1 << TWEA) | (0 << TWSTA) | (0 << TWSTO) |
      (0 << TWWC);
    break;
  }
}