功能实现背景介绍

本项目中，需要使用STM32的USART6串口与FPGA板（下位机）通信，需要发送和接收数据，有报文应答机制。

使用的报文规则如表格所示

板间报文的通信协议，校验使用的是和校验

U8 TX_CheckSum(U8 *buf, U8 len)//buf为数组，len为数组长度{ U8 i,ret= 0;for(i=0; i< len; i++) {ret+= *(buf++); }ret= ~ret;returnret; } U8 RX_CheckSum(U8 *buf, U8 len)//buf为数组，len为数组长度{ U8 i,ret= 0;for(i=0; i< len; i++) {ret+= *(buf++); }ret=ret;returnret+1; }

发送和接收的报文要满足不定长

HAL库的中断接收函数

如果要直接使用HAL库的中断接收函数，也就是HAL_UART_Receive_IT()函数

HAL_UART_Receive_IT(&huart6,UART6_RxBuffer,5); //下位机FPGA

在使用时，选择串口，选择接收的缓冲区，选择接收长度。

/** *@briefReceives an amount of data in non blocking mode. *@noteWhen UART parity is not enabled(PCE = 0), and Word Length is configured to 9 bits (M1-M0 = 01), * the received data is handled as a set of u16. In this case, Size must indicate the number * of u16 available through pData. *@paramhuart Pointer to a UART_HandleTypeDef structure that contains * the configuration information for the specified UART module. *@parampData Pointer to data buffer (u8 or u16 data elements). *@paramSize Amount of data elements (u8 or u16) to be received. *@retvalHAL status */HAL_StatusTypeDef HAL_UART_Receive_IT(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size) {/* Check that a Rx process is not already ongoing */if(huart- >RxState == HAL_UART_STATE_READY) {if((pData == NULL) || (Size == 0U)) {returnHAL_ERROR; }/* Process Locked */__HAL_LOCK(huart); huart- >pRxBuffPtr = pData; huart- >RxXferSize = Size; huart- >RxXferCount = Size; huart- >ErrorCode = HAL_UART_ERROR_NONE; huart- >RxState = HAL_UART_STATE_BUSY_RX;/* Process Unlocked */__HAL_UNLOCK(huart);/* Enable the UART Parity Error Interrupt */__HAL_UART_ENABLE_IT(huart, UART_IT_PE);/* Enable the UART Error Interrupt: (Frame error, noise error, overrun error) */__HAL_UART_ENABLE_IT(huart, UART_IT_ERR);/* Enable the UART Data Register not empty Interrupt */__HAL_UART_ENABLE_IT(huart, UART_IT_RXNE);returnHAL_OK; }else{returnHAL_BUSY; } }

这个函数本质上其实不是中断接收函数，只是配置函数，配置开启中断的信息，并且接收多少定长的数据结束本数据接收，串口的中断接收还是在中断中进行。

我们本次的长度虽然也是定长，但是有两种长度数据的接收，所以还是从设计接收不定长的数据为最终效果。

状态机的运用

对于不定长数据的接收，使用了状态机，分两次中断来接收数据

voidHAL_UART_RxCpltCallback(UART_HandleTypeDef *huart){if(huart- >Instance == USART6)// 判断是由哪个串口触发的中断{if(StateMachine_USART6)//状态机为1，都接收完毕，准备校验{if(re_flag6 ==1) { UART6_RxCounter =6; re_flag6 =0; }else{ len_counter6 =2+5+UART6_RxBuffer[2]+(UART6_RxBuffer[3]< <8);if(UART6_RxBuffer[len_counter6 -1] ==0x55&& UART6_RxBuffer[0] ==0xAA) { UART6_RxCounter = len_counter6; }else{memset(UART6_RxBuffer,0,0x400); UART6_RxCounter =0; } } StateMachine_USART6 =0;//状态机为0len_counter6 =0;HAL_UART_Receive_IT(&huart6,UART6_RxBuffer,5); }else//状态机为0，只接受到了前五个字节，继续接收后面的字节{if(UART6_RxBuffer[0] ==0xAA) { StateMachine_USART6 =1; UART6_RxCounter =5;if(UART6_RxBuffer[2] ==0&& UART6_RxBuffer[3] ==0) {HAL_UART_Receive_IT(&huart6,(uint8_t*)&UART6_RxBuffer[5],1); re_flag6 =1; }elseHAL_UART_Receive_IT(&huart6,(uint8_t*)&UART6_RxBuffer[5],2+ UART6_RxBuffer[2] + (UART6_RxBuffer[3] < <8)); }else{memset(UART6_RxBuffer,0,0x400); UART6_RxCounter =0;HAL_UART_Receive_IT(&huart6,UART6_RxBuffer,5); } } } }