c-SPI始终读取0

Question

我正在尝试将SPI接口与SPI ADXL345传感器和STM32F072 Nucleo板一起使用。我想做一个非常基本的读取操作。现在，读取功能在等待RXNE信号时被阻止。但RXNE从未设置。SPI始终读取0。我用IAR这里是我的代码，我用这些函数也写和读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 rn", 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_AF_1);
GPIO_PinAFConfig(GPIOA, 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);
}

Answer 1

您的初始化看起来相当完整，但我发现了一个错误：GPIO引脚A5/A6/A7需要设置为GPIO_AF_0(而不是GPIO_AF_1(，以便在这些引脚处获得SPI1 SCK/MISO/MOSI(见STM32F072数据表15(。这就是为什么您可能从RX FIFO中始终读取零的原因。

不过，我有点想知道RXNE标志没有设置。当SPI单元处于全双工主模式时，即使GPIO引脚配置不正确，它也应该为发送的每个字节接收一个字节。但我认为STM32F0处理这种情况的方式与旧款STM32L1不同：当我没有记错的时候，我确实注意到在STM32F0上，SPI接收器似乎从GPIO引脚获得时钟信号，而不是直接从SPI发送器(生成它(获得时钟信号。因此，错误配置的SCK引脚也可能解释SPI RX单元根本没有接收到任何东西。

Answer 2

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);
}