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    首先感谢电子产品世界和恩智浦公司的信任能够参加本次对FRDM-MCXA156开发板的评测。

    FRDM-MCXA156基于Arm Cortex-M33 拥有一个I3C接口。开发板板载P3T1755温度传感器可以通过I3C（12.5MHZ）和I2C(3.4MHZ)数据接口读取P3T1755寄存器。I3C的设备并不常见，之前少有涉猎，所以先从I3C入手开始评测。

    恩智浦提供了I3C相关例程，位于：SDK_2_16_100_FRDM-MCXA156\boards\frdmmcxa156\driver_examples\i3c\master_read_sensor_p3t1755

    本文试图对该例程进行解读。

一、硬件连接

通过I3C0(P0_16、P0_17)连接P3T1755。

二、P3T1755

    The P3T1755 is a temperature-to-digital converter from -40 °C to +125 °C range. It uses an on-chip band gap

temperature sensor and A-to-D conversion technique with an overtemperature detection. The device contains a

number of configuration and data registers to store the device settings, such as device operation mode, and a

temperature register (Temp) to store the digital temp reading that can be communicated by a controller via the

2-wire serial I3C (up to 12.5 MHz) and I2C (up to 3.4 MHz) interface.

SDA、SCL是I3C接口，在I3C模式下ALERT不起作用。A0、A1、A2用于用户自定义设备地址，开发板上这3个引脚接地。

P3T1755做为从机使用，数据手册上给出了地址的确定方法：

可以得出从机地址为0x48(SENSOR_SLAVE_ADDR)

三、源码解读

1、BOARD_InitPins();

初始化I3C0

  const port_pin_config_t port0_16_pin83_config = {/* Internal pull-up/down resistor is disabled */
                                                     kPORT_PullDisable,
                                                     /* Low internal pull resistor value is selected. */
                                                     kPORT_LowPullResistor,
                                                     /* Fast slew rate is configured */
                                                     kPORT_FastSlewRate,
                                                     /* Passive input filter is disabled */
                                                     kPORT_PassiveFilterDisable,
                                                     /* Open drain output is disabled */
                                                     kPORT_OpenDrainDisable,
                                                     /* Low drive strength is configured */
                                                     kPORT_LowDriveStrength,
                                                     /* Normal drive strength is configured */
                                                     kPORT_NormalDriveStrength,
                                                     /* Pin is configured as I3C0_SDA */
                                                     kPORT_MuxAlt10,
                                                     /* Digital input enabled */
                                                     kPORT_InputBufferEnable,
                                                     /* Digital input is not inverted */
                                                     kPORT_InputNormal,
                                                     /* Pin Control Register fields [15:0] are not locked */
                                                     kPORT_UnlockRegister};
    /* PORT0_16 (pin 83) is configured as I3C0_SDA */
    PORT_SetPinConfig(PORT0, 16U, &port0_16_pin83_config);

    const port_pin_config_t port0_17_pin84_config = {/* Internal pull-up/down resistor is disabled */
                                                     kPORT_PullDisable,
                                                     /* Low internal pull resistor value is selected. */
                                                     kPORT_LowPullResistor,
                                                     /* Fast slew rate is configured */
                                                     kPORT_FastSlewRate,
                                                     /* Passive input filter is disabled */
                                                     kPORT_PassiveFilterDisable,
                                                     /* Open drain output is disabled */
                                                     kPORT_OpenDrainDisable,
                                                     /* Low drive strength is configured */
                                                     kPORT_LowDriveStrength,
                                                     /* Normal drive strength is configured */
                                                     kPORT_NormalDriveStrength,
                                                     /* Pin is configured as I3C0_SCL */
                                                     kPORT_MuxAlt10,
                                                     /* Digital input enabled */
                                                     kPORT_InputBufferEnable,
                                                     /* Digital input is not inverted */
                                                     kPORT_InputNormal,
                                                     /* Pin Control Register fields [15:0] are not locked */
                                                     kPORT_UnlockRegister};
    /* PORT0_17 (pin 84) is configured as I3C0_SCL */
    PORT_SetPinConfig(PORT0, 17U, &port0_17_pin84_config);

2、I3C初始化

    I3C_MasterGetDefaultConfig(&masterConfig);
    masterConfig.baudRate_Hz.i2cBaud          = EXAMPLE_I2C_BAUDRATE;
    masterConfig.baudRate_Hz.i3cPushPullBaud  = EXAMPLE_I3C_PP_BAUDRATE;
    masterConfig.baudRate_Hz.i3cOpenDrainBaud = EXAMPLE_I3C_OD_BAUDRATE;
    masterConfig.enableOpenDrainStop          = false;
    masterConfig.disableTimeout               = true;
    I3C_MasterInit(EXAMPLE_MASTER, &masterConfig, I3C_MASTER_CLOCK_FREQUENCY);

    /* Create I3C handle. */
    I3C_MasterTransferCreateHandle(EXAMPLE_MASTER, &g_i3c_m_handle, &masterCallback, NULL);

3、设置P3T1755动态地址p3t1755_set_dynamic_address（）

#define SENSOR_SLAVE_ADDR          0x48U

#define SENSOR_ADDR 0x08U
#define CCC_RSTDAA  0x06U
#define CCC_SETDASA 0x87
status_t p3t1755_set_dynamic_address(void)
{
    status_t result                  = kStatus_Success;
    i3c_master_transfer_t masterXfer = {0};
    uint8_t g_master_txBuff[1];

    /* Reset dynamic address. */
    g_master_txBuff[0]      = CCC_RSTDAA;
    masterXfer.slaveAddress = 0x7E;
    masterXfer.data         = g_master_txBuff;
    masterXfer.dataSize     = 1;
    masterXfer.direction    = kI3C_Write;
    masterXfer.busType      = kI3C_TypeI3CSdr;
    masterXfer.flags        = kI3C_TransferDefaultFlag;
    result                  = I3C_MasterTransferBlocking(EXAMPLE_MASTER, &masterXfer);
    if (result != kStatus_Success)
    {
        return result;
    }

    /* Assign dynmic address. */
    memset(&masterXfer, 0, sizeof(masterXfer));
    g_master_txBuff[0]      = CCC_SETDASA;
    masterXfer.slaveAddress = 0x7E;
    masterXfer.data         = g_master_txBuff;
    masterXfer.dataSize     = 1;
    masterXfer.direction    = kI3C_Write;
    masterXfer.busType      = kI3C_TypeI3CSdr;
    masterXfer.flags        = kI3C_TransferNoStopFlag;
    result                  = I3C_MasterTransferBlocking(EXAMPLE_MASTER, &masterXfer);
    if (result != kStatus_Success)
    {
        return result;
    }

    memset(&masterXfer, 0, sizeof(masterXfer));
    g_master_txBuff[0]      = SENSOR_ADDR << 1;
    masterXfer.slaveAddress = SENSOR_SLAVE_ADDR;
    masterXfer.data         = g_master_txBuff;
    masterXfer.dataSize     = 1;
    masterXfer.direction    = kI3C_Write;
    masterXfer.busType      = kI3C_TypeI3CSdr;
    masterXfer.flags        = kI3C_TransferDefaultFlag;
    return I3C_MasterTransferBlocking(EXAMPLE_MASTER, &masterXfer);
}

这一步基于数据手册的这个图解：

在 p3t1755_set_dynamic_address(void)中，首先对地址做了一个复位操作，然后将I3C从机指定地址为SENSOR_ADDR（0x08U），考虑到I3C是7h（7位），所以做了一个SENSOR_ADDR << 1左移1位的操作。

CCC是I3C Common Command Codes的缩写。P3T1755 supports CCCs that allow the controller to control multiple targets through a broadcast command at once or individual targets through direct commands这些指令如下：

本例中用到了0x06、0x87指令。

RESET 地址，需要发送0X7E，0x06

设置动态地址：

4、p3t1755初始化

    p3t1755Config.writeTransfer = I3C_WriteSensor;
    p3t1755Config.readTransfer  = I3C_ReadSensor;
    p3t1755Config.sensorAddress = SENSOR_ADDR;
    P3T1755_Init(&p3t1755Handle, &p3t1755Config);

指定了I3C读写p3t1755寄存器的处理函数和I3C从机地址。

5、I3C_ReadSensor（）

P3T1755_ReadReg函数会调用I3C_ReadSensor。

status_t I3C_ReadSensor(uint8_t deviceAddress, uint32_t regAddress, uint8_t *regData, size_t dataSize)
{
    status_t result                  = kStatus_Success;
    i3c_master_transfer_t masterXfer = {0};
    uint32_t timeout                 = 0U;

    masterXfer.slaveAddress   = deviceAddress;
    masterXfer.direction      = kI3C_Read;
    masterXfer.busType        = kI3C_TypeI3CSdr;
    masterXfer.subaddress     = regAddress;
    masterXfer.subaddressSize = 1;
    masterXfer.data           = regData;
    masterXfer.dataSize       = dataSize;
    masterXfer.flags          = kI3C_TransferDefaultFlag;

    g_masterCompletionFlag = false;
    g_completionStatus     = kStatus_Success;
    result                 = I3C_MasterTransferNonBlocking(EXAMPLE_MASTER, &g_i3c_m_handle, &masterXfer);
    if (kStatus_Success != result)
    {
        return result;
    }

    while (!g_masterCompletionFlag)
    {
        timeout++;
        if ((g_completionStatus != kStatus_Success) || (timeout > I3C_TIME_OUT_INDEX))
        {
            break;
        }
    }

    if (timeout == I3C_TIME_OUT_INDEX)
    {
        result = kStatus_Timeout;
    }
    result = g_completionStatus;

    return result;
}

I3C_MasterTransferNonBlocking向从机发送I3C数据实现读取P3T1755寄存器。

regAddress取值：

6、温度读取及计算

/* Registers. */
#define P3T1755_TEMPERATURE_REG (0x00U)
#define P3T1755_CONFIG_REG      (0x01U)
status_t P3T1755_ReadTemperature(p3t1755_handle_t *handle, double *temperature)
{
    status_t result = kStatus_Success;
    uint8_t data[2];
    uint16_t temp;

    result = P3T1755_ReadReg(handle, P3T1755_TEMPERATURE_REG, &data[0], 2);
    if (result == kStatus_Success)
    {
        temp = (((uint16_t)data[0] << 8U) | (uint16_t)data[1]) >> 4U;
        *temperature = (double)temp * 0.0625;
    }

    return result;
}

四、运行效果