SPI是一種高速的，全雙工，同步的通信總線，原理和使用簡單，占用引腳資源少，是一種常用的通信方式。
STM32通常有2~3個SPI接口
根據STM32手冊的使用方法：
1. Enable peripheral clock
2. Enable SCK, MOSI, MISO and NSS GPIO clocks
3. Peripherals alternate function:
? Connect the pin to the desired peripherals' Alternate Function (AF)
? Call GPIO_Init() function.
4. Program the Polarity, Phase, First Data, Baud Rate Prescaler, Slave Management,Peripheral Mode and CRC Polynomial values using the SPI_Init() function in SPI mode.
5. Configure the FIFO threshold using SPI_RxFIFOThresholdConfig() to select at which hreshold the RXNE event is generated.
6. Enable the NVIC and the corresponding interrupt using the function SPI_I2S_ITConfig() if you need to use interrupt mode.
7. When using the DMA mode
? Configure the DMA using DMA_Init() function.
? Active the needed channel Request using SPI_I2S_DMACmd() function.
8. Enable the SPI using the SPI_Cmd() function .
9. Enable the DMA using the DMA_Cmd() function when using DMA mode.
10. To use the CRC Hardware calculation feature refer to the Peripheral CRC hardware Calculation subsection.
基于STM32F3discovery開發(fā)板，STM32F303VC
使用SPI1,從機連接的是L3GD20陀螺儀，引腳連接：
SPI1_MOSI——PA7
SPI1_SCK——PA5
SPI1_MISO——PA6
NSS——PE3
代碼：
void SPI_GPIO_Config(void)
{
//將SPI1_MOSI—PA7,SPI1_SCK—PA5,SPI1_MISO—PA6引腳配置為對應復用功能
//NSS—PE3為從機片選引腳，配置為推挽輸出
}
void SPI_Config(void)
{
SPI_InitTypeDef SPI_InitStructure;
SPI_InitStructure.SPI_Direction =SPI_Direction_2Lines_FullDuplex;
SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low; //結合從機選擇
SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge; //結合從機選擇
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = 7;
SPI_I2S_DeInit(SPI1);
SPI_Init(SPI1, &SPI_InitStructure);
SPI_RxFIFOThresholdConfig(SPI1, SPI_RxFIFOThreshold_QF);
SPI_Cmd(SPI1,ENABLE);
}
然后就可以用SPI接口進行收發(fā)數據，具體收發(fā)方式要根據從機設備決定
需要的時候可以配置中斷，DMA等功能
發(fā)送或接收數據前，先將相應從機的片選信號置零
SPI是兩個設備移位寄存器的數據交換，接收數據前先向從機發(fā)送虛擬字節(jié)，收到的數據就是所要讀取的數據
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