SPI总是读0

问题描述

我正在尝试将SPI接口与SPI ADXL345传感器和STM32F072 Nucleo板配合使用，我想进行非常基本的读取操作，但现在在等待RXNE信号时读取功能被阻止了，但是RXNE从不停止设置。 SPI始终读取0。我使用IAR，这是我的代码，我也使用这些功能来读写SPI。

int main()
{

    USART2_Init();
    SPIx_Init();

    while (1) {
        adxl_baslat();
        receiveData[0] = readData(0x32);
        receiveData[1] = readData(0x33);
        receiveData[2] = readData(0x34);
        receiveData[3] = readData(0x35);
        receiveData[4] = readData(0x36);
        receiveData[5] = readData(0x37);

        x = (receiveData[1] << 8) | (receiveData[0]);
        y = (receiveData[3] << 8) | (receiveData[2]);
        z = (receiveData[5] << 8) | (receiveData[4]);
        xg = (float)x * 0.0078;
        yg = (float)x * 0.0078;
        zg = (float)x * 0.0078;
        sprintf(buffer,"xg: %f yg: %f zg: %f \r\n",xg,yg,zg);
        USART_PutString(buffer);
    }
}

void SPIx_Init()
{

    SPI_InitTypeDef SPI_InitStruct;
    GPIO_InitTypeDef GPIO_InitStruct;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1,ENABLE);
    SPI_InitStruct.SPI_BaudratePrescaler = SPI_BaudratePrescaler_16;
    SPI_InitStruct.SPI_CPHA = SPI_CPHA_2Edge;
    SPI_InitStruct.SPI_CPOL = SPI_CPOL_High;
    SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b;
    SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStruct.SPI_Mode = SPI_Mode_Master;
    SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set;
    SPI_Init(SPI1,&SPI_InitStruct);
    SPI_Cmd(SPI1,ENABLE);
    SPI_DataSizeConfig(SPI1,ENABLE);
    SPI_RxFIFOThresholdConfig(SPI1,SPI_RxFIFOThreshold_QF);

    // Step 2: Initialize GPIO
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE);
    // GPIO pins for MOSI,MISO,and SCK
    GPIO_InitStruct.GPIO_Pin = SPI_PIN_MOSI | SPI_PIN_MISO | SPI_PIN_SCK;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;

    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_10MHz;
    GPIO_Init(GPIOA,&GPIO_InitStruct);

    GPIO_PinAFConfig(GPIOA,GPIO_PinSource5,GPIO_AF_1);
    GPIO_PinAFConfig(GPIOA,GPIO_PinSource6,GPIO_PinSource7,GPIO_AF_1);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB,ENABLE);
    GPIO_InitStruct.GPIO_Pin = SPI_PIN_SS;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_10MHz;

    GPIO_Init(GPIOB,&GPIO_InitStruct);
}

uint8_t sendByte(uint8_t bytetoSend)
{
    timeout = TIMEOUT_TIME;
    while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE) == RESET) & (timeout != 0)) {
        timeout--;
    }
    SPI_SendData8(SPI1,bytetoSend);
    timeout = TIMEOUT_TIME;
    while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE) == RESET) & (timeout != 0)) {
        timeout--;
    }
    return (uint8_t)SPI_ReceiveData8(SPI1);
}

void writeData(uint8_t address,uint8_t dataToWrite)
{

    DATA2 = address | 0x40;
    GPIO_ResetBits(GPIOB,GPIO_Pin_9);
    sendByte(DATA2);
    sendByte(dataToWrite);

    GPIO_SetBits(GPIOB,GPIO_Pin_9);
}

uint8_t readData(uint8_t address)
{
    address |= 0x40;
    address |= 0x80;
    GPIO_ResetBits(GPIOB,GPIO_Pin_9);
    sendByte(address);
    tempByte = sendByte(address);
    GPIO_SetBits(GPIOB,GPIO_Pin_9);
    return tempByte;
}

void adxl_baslat(void)
{
    writeData(0x31,0x01);
    writeData(0x2d,0x00);
    writeData(0x2d,0x08);
}

解决方法

您的初始化看起来很完整，但是我发现了一个错误： GPIO引脚A5 / A6 / A7需要设置为GPIO_AF_0（而不是GPIO_AF_1），以便在这些引脚上获得SPI1 SCK / MISO / MOSI（请参见STM32F072数据表表15）。这就是为什么您可能总是从RX FIFO读取零的原因。

我有点想知道未设置RXNE标志。当SPI单元处于全双工主模式时，即使未正确配置GPIO引脚，它也应为每个发送的字节接收一个字节。但是我认为STM32F0处理这种情况的方式与旧的STM32L1不同：当我没记错的时候，我确实注意到在STM32F0上，SPI接收器似乎从GPIO引脚而不是直接从SPI发送器（产生它）获取时钟信号。因此，错误配置的SCK引脚也可能说明SPI RX单元什么也没收到。

,

在接收有意义的数据之前，您需要清除接收FIFO或DR

uint8_t sendByte(uint8_t byteToSend)
{
    timeout = TIMEOUT_TIME;
    while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE) != RESET) 
    {
        uint8_t dummy;
        dummy = *(volatile uint8_t *)&SPI1 -> DR;
    }
    timeout = TIMEOUT_TIME;
    while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE) == RESET) & (timeout != 0)) {
        timeout--;
    }
    SPI_SendData8(SPI1,byteToSend);
    timeout = TIMEOUT_TIME;
    while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE) == RESET) & (timeout != 0)) {
        timeout--;
    }
    return (uint8_t)SPI_ReceiveData8(SPI1);
}