STM32的SPI总是出现模式错误标志SPI_FLAG_MODF置位的问题

问题描述： 今天在调试SPI程序，调试的时候程序总是死在while((SPIx->SR&SPI_I2S_FLAG_RXNE)==0);判断语句里，查看SPIx->SR发现值为0x0020，也就是SPI_FLAG_MODF被置位了，我的初始化程序如下：

1. void SPI_Configuration(SPI_TypeDef* SPIx)
2. {
3. SPI_InitTypeDef SPI_InitStruct;
5. SPI_RCC_Configuration(SPIx);
7. SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_32;
8. SPI_InitStruct.SPI_Direction= SPI_Direction_2Lines_FullDuplex;
9. SPI_InitStruct.SPI_Mode = SPI_Mode_Master;
10. SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b;
11. SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;
12. SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;
13. SPI_InitStruct.SPI_NSS = SPI_NSS_Hard;
14. SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;
15. SPI_InitStruct.SPI_CRCPolynomial = 7;
16. SPI_Init(SPIx, &SPI_InitStruct);
18. SPI_GPIO_Configuration(SPIx);
20. SPI_Cmd(SPIx, ENABLE);
21. }

复制代码 时钟和引脚都是配置正确的。 解决办法： 将SPI_InitStruct.SPI_NSS = SPI_NSS_Hard改为SPI_InitStruct.SPI_NSS = SPI_NSS_Soft。或者增加SPI_SSOutputCmd(SPIx, ENABLE)语句。 程序如下：

1. void SPI_Configuration(SPI_TypeDef* SPIx)
2. {
3. SPI_InitTypeDef SPI_InitStruct;
5. SPI_RCC_Configuration(SPIx);
7. SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_32;
8. SPI_InitStruct.SPI_Direction= SPI_Direction_2Lines_FullDuplex;
9. SPI_InitStruct.SPI_Mode = SPI_Mode_Master;
10. SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b;
11. SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;
12. SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;
13. SPI_InitStruct.SPI_NSS = SPI_NSS_Hard;
14. SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;
15. SPI_InitStruct.SPI_CRCPolynomial = 7;
16. SPI_Init(SPIx, &SPI_InitStruct);
18. SPI_GPIO_Configuration(SPIx);
20. SPI_SSOutputCmd(SPIx, ENABLE);
21. SPI_Cmd(SPIx, ENABLE);
22. }

复制代码