写一个iic驱动代码样例

以下是一个I2C驱动程序的示例代码：

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

#define I2C_WRITE_ADDRESS 0xA0
#define I2C_READ_ADDRESS 0xA1
#define I2C_BUFFER_SIZE 64

volatile uint8_t i2cTxBuffer[I2C_BUFFER_SIZE];
volatile uint8_t i2cRxBuffer[I2C_BUFFER_SIZE];
volatile uint8_t i2cTxIndex = 0;
volatile uint8_t i2cRxIndex = 0;
volatile uint8_t i2cTxCount = 0;
volatile uint8_t i2cRxCount = 0;
volatile uint8_t i2cStatus = 0;

void i2cInit(void) {
    TWBR = 72;  // Set the I2C clock rate to 100 kHz
    TWCR = (1 << TWEN);  // Enable I2C
    TWCR |= (1 << TWIE);  // Enable I2C interrupt
}

void i2cSend(uint8_t address, uint8_t* data, uint8_t length) {
    i2cTxIndex = 0;
    i2cTxCount = length;
    for (uint8_t i = 0; i < length; i++) {
        i2cTxBuffer[i] = data[i];
    }
    i2cStatus = 0;
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN) | (1 << TWIE);
    while (i2cStatus == 0) {
        // Wait for the I2C transaction to complete
    }
}

void i2cReceive(uint8_t address, uint8_t* data, uint8_t length) {
    i2cRxIndex = 0;
    i2cRxCount = length;
    i2cStatus = 0;
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN) | (1 << TWIE);
    while (i2cStatus == 0) {
        // Wait for the I2C transaction to complete
    }
    for (uint8_t i = 0; i < length; i++) {
        data[i] = i2cRxBuffer[i];
    }
}

ISR(TWI_vect) {
    uint8_t status = TWSR & 0xF8;
    switch (status) {
        case TW_START:
        case TW_REP_START:
            if (i2cTxCount > 0) {
                TWDR = I2C_WRITE_ADDRESS;
                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE);
                i2cStatus = 1;
            } else {
                TWDR = I2C_READ_ADDRESS;
                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE);
                i2cStatus = 2;
            }
            break;
        case TW_MT_SLA_ACK:
        case TW_MT_DATA_ACK:
            if (i2cTxIndex < i2cTxCount) {
                TWDR = i2cTxBuffer[i2cTxIndex++];
                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE);
            } else {
                TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN) | (1 << TWIE);
                i2cStatus = 3;
            }
            break;
        case TW_MR_DATA_ACK:
            i2cRxBuffer[i2cRxIndex++] = TWDR;
            if (i2cRxIndex < i2cRxCount) {
                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE) | (1 << TWEA);
            } else {
                TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN) | (1 << TWIE);
                i2cStatus = 4;
            }
            break;
        case TW_MR_SLA_ACK:
            if (i2cRxCount == 1) {
                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE) | (1 << TWIE);
            } else {
                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE) | (1 << TWEA);
            }
            break;
        default:
            TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN) | (1 << TWIE);
            i2cStatus = 255;
            break;
    }
}

这个代码实现了基本的I2C通信，允许主机以单字节形式写入和读取从机设备。它使用I2C的硬件模块与处理器的I2C外设通信，并在发生交互和错误时发出中断。在I2C交互期间，它使用一个状态机变量来跟踪进度，从而正确处理发送和接收的消息。它还允许发送和接收多个字节。