Question

我使用的是MPLABX 3.10，并使用MSSPI2C主中断功能生成了I2C主接口。我能够在一个振荡器上生成一个I2C写入事件对我来说没问题。然而，读取失败。当我查看示波器输出时，我可以清楚地看到生成了启动条件，并且生成了具有读取位设置的设备ID并激活。接下来我希望看到寄存器地址消失，但我看到全部为零。我是否错误地使用了生成的代码？我需要进行设备写入，然后读取设备吗？我尝试将代码缩减为以下内容：

void I2C_Initialize(void) {
    i2c_object.pTrHead = i2c_tr_queue;
    i2c_object.pTrTail = i2c_tr_queue;
    i2c_object.trStatus.s.empty = true;
    i2c_object.trStatus.s.full = false;

    i2c_object.i2cErrors = 0;

    // BF RCinprocess_TXcomplete; UA dontupdate; SMP Sample At Middle; P stopbit_notdetected; S startbit_notdetected; R_nW write_noTX; CKE Idle to Active; D_nA lastbyte_address; 
    SSP1STAT = 0x00;
    // SSPEN enabled; WCOL no_collision; SSPOV no_overflow; CKP Idle:Low, Active:High; SSPM FOSC/4_SSPxADD; 
    SSP1CON1 = 0x28;
    // BOEN disabled; AHEN disabled; SBCDE disabled; SDAHT 100ns; DHEN disabled; ACKTIM ackseq; PCIE disabled; SCIE disabled; 
    SSP1CON3 = 0x00;
    // Baud Rate Generator Value: SSPADD 3;   
    SSP1ADD = 0x03;

    /* Byte sent or received */
    // clear the master interrupt flag
    PIR1bits.SSP1IF = 0;
    // enable the master interrupt
    PIE1bits.SSP1IE = 1;

}

void I2C_MasterRead(
        uint8_t *pdata,
        uint8_t length,
        uint16_t address,
        I2C_MESSAGE_STATUS *pflag) {
    static I2C_TRANSACTION_REQUEST_BLOCK trBlock;


    // check if there is space in the queue
    if (i2c_object.trStatus.s.full != true) {
        I2C_MasterReadTRBBuild(&trBlock, pdata, length, address);
        I2C_MasterTRBInsert(1, &trBlock, pflag);
    } else {
        *pflag = I2C_MESSAGE_FAIL;
    }

}

void I2C_MasterReadTRBBuild(
        I2C_TRANSACTION_REQUEST_BLOCK *ptrb,
        uint8_t *pdata,
        uint8_t length,
        uint16_t address) {
    ptrb->address = address << 1;
    // make this a read
    ptrb->address |= 0x01;
    ptrb->length = length;
    ptrb->pbuffer = pdata;
}

void main(void) {
    #define BMA222E_BASE_ADDRESS_DEV0 (0x18) // <BMA222E base address
    uint8_t dummy[2];
    I2C_MESSAGE_STATUS pflag;
    /* Configure the oscillator for the device */

    ConfigureOscillator();
    I2C_Initialize();


    dummy[0] = 0x0F;  // I expect to see 0x0F go out as the register value
    dummy[1] = 0x00;
    I2C_MasterRead (&dummy, 2, BMA222E_BASE_ADDRESS_DEV0, &pflag);
}

Answer 1

好的，所以想通了。我需要写入地址，然后分两步读取数据。我修改了main函数如下。

void main(void) {
    #define BMA222E_BASE_ADDRESS_DEV0 (0x18) // <BMA222E base address
    uint8_t dummy[2];
    I2C_MESSAGE_STATUS pflag;
    /* Configure the oscillator for the device */
    ConfigureOscillator();
    I2C_Initialize();


    dummy[0] = 0x0F;  // I expect to see 0x0F go out as the register value
    dummy[1] = 0x00;
    I2C_MasterWrite (&dummy, 1, BMA222E_BASE_ADDRESS_DEV0, &pflag);
    I2C_MasterRead (&dummy, 1, BMA222E_BASE_ADDRESS_DEV0, &pflag);

    // dummy[0] now contains the read data.
}

PIC单片机I2C读取失败，使用MPLABX生成的代码

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