两块STM32F4之间spi握手通信问题

2019-03-23 19:16发布

站内问答 / STM32/STM8
8376 3 1394
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：
  1. GPIO_InitTypeDef GPIO_InitStruct;        SPI_InitTypeDef SPI_InitStruct;
  2.         // 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);
  3.         // 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);
  4.         SPI_Cmd(SPI1, ENABLE); // enable SPI1
复制代码主机的发送接收函数：
  1. uint8_t SPI1_sendrecv(uint8_t data){
  2.         SPI1->DR = data; // write data to be transmitted to the SPI data register        while( !(SPI1->SR & SPI_I2S_FLAG_TXE) ); // wait until transmit complete        while( !(SPI1->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete        while( SPI1->SR & SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore        return SPI1->DR; // return received data from SPI data register}
复制代码主机主函数发送：
  1. for(index_data=0;index_data复制代码从机的配置：



    4. void init_SPI1(void){        GPIO_InitTypeDef GPIO_InitStruct;        SPI_InitTypeDef SPI_InitStruct;
    5.         // 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);
    6.         SPI_Cmd(SPI1, ENABLE); // enable SPI1}
    复制代码从机发送和接收函数：
    1. 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        }
    2. 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}
    复制代码从机主函数接收：
    1. while(1){        if(index_spi==BufferSize){                                        index_spi=0;                printf("%s ",receive_data);        }        else{                                                                receive_data[index_spi]=SPI1_Receive();                 SPI1_Send(receive_data[index_spi]);                index_spi++;        }
    复制代码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：
    1. for(index_data=0;index_data                }               for(j=0;j<4;j++){                                        ack_string[j]=SPI1_sendrecv(0x00);                }                printf("%s ",receive_data);                                        printf("ack string: %s ",ack_string);
    复制代码从机主函数接收：
    1. char ack_string[4]="GOOD";while(1){        if(index_spi==BufferSize){                                        index_spi=0;                printf("%s ",receive_data);                       for(i=0;i<4;i++){                        SPI1_Receive();                        SPI1_Send(ack_string[i]);                }        }        else{                                                                receive_data[index_spi]=SPI1_Receive();                 SPI1_Send(receive_data[index_spi]);                index_spi++;        }}
    复制代码主机发送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。 此帖出自小平头技术问答
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3条回答
hjf2002
2019-03-24 07:30
楼上说的很有道理。

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