两块STM32F4之间spi握手通信移位问题

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我用两块STM32F4的SPI1双向通信，想实现主SPI发送1024个数据，从SPI收到的时候回复一个ack，主SPI收到这个ack的时候再发送1024个字节。有好几个问题想请教大侠。

首先主SPI的配置如下：

        GPIO_InitTypeDef GPIO_InitStruct;

SPI_InitTypeDef SPI_InitStruct;

// enable clock for used IO pins

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_4 | GPIO_Pin_3;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;

GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOB, &GPIO_InitStruct);

// connect SPI1 pins to SPI alternate function

GPIO_PinAFConfig(GPIOB, GPIO_PinSource5, GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource4, GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource3, GPIO_AF_SPI1);

// enable peripheral clock

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

/* configure SPI1 in Mode 0 

* CPOL = 0 --> clock is low when idle

* CPHA = 0 --> data is sampled at the first edge

*/

SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines

SPI_InitStruct.SPI_Mode = SPI_Mode_Master;     // transmit in master mode, NSS pin has to be always high

SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide

SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;        // clock is low when idle

SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;      // data sampled at first edge

SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set; // set the NSS management to internal and pull internal NSS high

SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_16; // SPI frequency is APB2 frequency / 4

SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first

SPI_InitStruct.SPI_CRCPolynomial = 7;

SPI1->CR1 |=0x1000;

SPI1->CR2 |=0x20;

SPI_Init(SPI1, &SPI_InitStruct); 

SPI_Cmd(SPI1, ENABLE); // enable SPI1[/code]主机的发送接收函数：

1. uint8_t SPI1_sendrecv(uint8_t data){</div>
2. <div><br />
3. </div>
4. <div><span class="Apple-tab-span" style="white-space:pre;"> </span>SPI1-&gt;DR = data; // write data to be transmitted to the SPI data register</div>
5. <div><span class="Apple-tab-span" style="white-space:pre;"> </span>while( !(SPI1-&gt;SR &amp; SPI_I2S_FLAG_TXE) ); // wait until transmit complete</div>
6. <div><span class="Apple-tab-span" style="white-space:pre;"> </span>while( !(SPI1-&gt;SR &amp; SPI_I2S_FLAG_RXNE) ); // wait until receive complete</div>
7. <div><span class="Apple-tab-span" style="white-space:pre;"> </span>while( SPI1-&gt;SR &amp; SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore</div>
8. <div><span class="Apple-tab-span" style="white-space:pre;"> </span>return SPI1-&gt;DR; // return received data from SPI data register</div>
9. <div>}<br />
10. <br />
11. 主机主函数发送：<br />
12. <br />
13. for(index_data=0;index_data&lt;BufferSize;index_data++){</div>
14. <div>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;receive_data[index_data]=SPI1_sendrecv(send_data[index_data]);</div>
15. <div>}</div>
16. <div>printf("%s\n\r",receive_data);

复制代码

从机的配置：[code]void init_SPI1(void){

GPIO_InitTypeDef GPIO_InitStruct;

SPI_InitTypeDef SPI_InitStruct;

// enable clock for used IO pins

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_4 | GPIO_Pin_3;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;

GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOB, &GPIO_InitStruct);

// connect SPI1 pins to SPI alternate function

GPIO_PinAFConfig(GPIOB, GPIO_PinSource3, GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource4, GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource5, GPIO_AF_SPI1);

// enable peripheral clock

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

/* configure SPI1 in Mode 0 

* CPOL = 0 --> clock is low when idle

* CPHA = 0 --> data is sampled at the first edge

*/

SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines

SPI_InitStruct.SPI_Mode = SPI_Mode_Slave;     // transmit in master mode, NSS pin has to be always high

SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide

SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;        // clock is low when idle

SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;      // data sampled at first edge

SPI_InitStruct.SPI_NSS = SPI_NSS_Soft;  // set the NSS management to software

SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first

SPI_InitStruct.SPI_CRCPolynomial = 7;

SPI1->CR1 |=0x1000;

SPI1->CR2 |=0x20;

SPI_Init(SPI1, &SPI_InitStruct); 

SPI_Cmd(SPI1, ENABLE); // enable SPI1

}

从机发送和接收函数：

void SPI1_Send(uint8_t data){

SPI1->DR = data; // write data to be transmitted to the SPI data register

while( !(SPI1->SR & SPI_I2S_FLAG_TXE) ); // wait until transmit complete

}

uint8_t SPI1_Receive(void){

while( !(SPI1->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete

return SPI1->DR; // return received data from SPI data register

}

从机主函数接收：

while(1){

if(index_spi==BufferSize){

index_spi=0;

       printf("%s\n\r",receive_data);

}

else{

receive_data[index_spi]=SPI1_Receive(); 

SPI1_Send(receive_data[index_spi]);

index_spi++;

}

1. 首先测试两个之间就只是双向发送和接收，接收到的结果会有一位的偏移，比如我发一段字节：Google Inc. is an American multinational 

从机收到：lGoogle Inc. is an American multinationa，从机主机都是同时收发。从机收到一个字节就同时发回这个字节。然后主机收到的也是lGoogle Inc. is an American multinationa，不知道这个是不是正常的，有没有大侠能解释下这一位的偏移是怎么回事？

2. 然后加上握手部分，希望主机发完字符串然后发送无用字节并等待回复，从机收完字符串之后收无用字符并同时发出确认字节。

主机主函数发送：    

for(index_data=0;index_data<BufferSize;index_data++){

                   receive_data[index_data]=SPI1_sendrecv(send_data[index_data]);

}

               for(j=0;j<4;j++){

ack_string[j]=SPI1_sendrecv(0x00);

}

printf("%s\n\r",receive_data);

printf("ack string: %s\n\r",ack_string);

从机主函数接收：

char ack_string[4]="GOOD";

while(1){

if(index_spi==BufferSize){

index_spi=0;

       printf("%s\n\r",receive_data);

                for(i=0;i<4;i++){

SPI1_Receive();

SPI1_Send(ack_string);

       }

}

else{

receive_data[index_spi]=SPI1_Receive(); 

SPI1_Send(receive_data[index_spi]);

index_spi++;

}

}

主机发送Google Inc. is an American multinational，

从机收到gle Inc. is an American multinational

主机收到的字符串GOODgle Inc. is an American multinationa

收到的ack string是ack string: l  

所以结果好像是从机回复的ack主机都在下一次收数据的时候才收到了。这个也很难理解，而且我试过了不管ack设多长，主机都是后面一步才在一串数据的开头收到这段ack。

正点原子

移位问题,可能和你数据处理有关.重点检查下.