SPI从机接收只能接收两个字节

xrfsmile

[mw_shl_code=c,true]#include "spi.h" #include "led.h" #include "mystring.h" #include <string.h> #include <stdio.h> #include "stm32f10x_spi.h" uint8_t cnt=0; void SPI1_Init(void) { GPIO_InitTypeDef GPIO_InitStructure; SPI_InitTypeDef SPI_InitStructure; NVIC_InitTypeDef NVIC_InitStructure; RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE); GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5|GPIO_Pin_7; GPIO_Init(GPIOA,&GPIO_InitStructure); GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;//miso GPIO_Init(GPIOA,&GPIO_InitStructure); GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;//cs GPIO_Init(GPIOA,&GPIO_InitStructure);     SPI_Cmd(SPI1, DISABLE);     SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;     SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;     SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;      SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;      SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;     SPI_InitStructure.SPI_NSS = SPI_NSS_Soft; //     SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_256;     SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;//SPI_FirstBit_MSB;     SPI_InitStructure.SPI_CRCPolynomial = 7;     SPI_Init(SPI1, &SPI_InitStructure); NVIC_InitStructure.NVIC_IRQChannel = SPI1_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); SPI_I2S_ClearFlag(SPI1, SPI_I2S_FLAG_RXNE); SPI_I2S_ITConfig(SPI1,SPI_I2S_IT_RXNE,ENABLE); /*Enable SPI1.NSS as a GPIO*/ //SPI_SSOutputCmd(SPI1, ENABLE); SPI_Cmd(SPI1, ENABLE); //spi1_cs_low; } void SPI1_SetSpeed(u8 SPI_BaudRatePrescaler) { assert_param(IS_SPI_BAUDRATE_PRESCALER(SPI_BaudRatePrescaler)); SPI1->CR1&=0XFFC7; SPI1->CR1|=SPI_BaudRatePrescaler; SPI_Cmd(SPI1,ENABLE); } u8 SPI1_ReadWriteByte(u8 TxData) { u8 retry=0; while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET)[/mw_shl_code] [mw_shl_code=c,true]       { retry++; if(retry>200)return 0;[/mw_shl_code] [mw_shl_code=c,true]        } SPI_I2S_SendData(SPI1, TxData); retry=0; while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET) { retry++; if(retry>200)return 0; } return SPI_I2S_ReceiveData(SPI1); } void SPI1_IRQHandler(void) { if(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == SET) { uint8_t RxVal1 = SPI_I2S_ReceiveData(SPI1); SaveCharToRxBuff((char)RxVal1); } }[/mw_shl_code] [mw_shl_code=c,true] [/mw_shl_code] [mw_shl_code=c,true]如上配置，SPI从机通讯只能接收两个字节，不知道怎么回事，哪位大神帮忙看看。[/mw_shl_code]

xuande

只要能正确地收（同时也有发）到一个字节，配置应当没错。

SPI每次只能处理一个字节，要收第3个字节，你必须启动第3次操作。
LZ给的程序，没有显示如何启动的信息。

另外，SPI1_ReadWriteByte函数里存在return语句，
如果return了，下面的判断就会被忽略。这逻辑可能有点问题。

xrfsmile

回复【2楼】xuande:
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我的是从机模式，怎么样启动第三次接收？不明白，请大神教教。

xuande

回复【3楼】xrfsmile:
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从机只能等待，所以主机必须主动。

xrfsmile

问题解决了，我接收到字节后，用snprintf函数转换成字符 串，然后用USB的HID方式返回给单片机多功能调试助手的，这过程花的时间比较长。所以没有看到所有的字节。