can.c

stm32初级例程

/*----------------------------------------------------------------------------
CAN实验需要两个带CAN接口的板子
CAN实验太复杂了，所以不是简单的配置文件能搞定的事，建议熟悉了STM32后再来做此实验。
准备工作，准备两个CAN板子，连接两个CAN接口，两个板子都下载本程序。
本实验通过CAN总线控制另外一个板子的LED2~LED5闪烁的例子，如果通信正常可以看到两个板子的LED都再闪烁，
如果通信失败或者断开通信线，LED不再闪烁

 *---------------------------------------------------------------------------*/

#include <stm32f10x_lib.h>                        // STM32F10x Library Definitions
#include "STM32_Reg.h"                            // STM32 register and bit Definitions
#include "STM32_Init.h"                           // STM32 Initialization
#include "CAN.h"                                  // STM32 CAN adaption layer

// CAN messge for sending
//CAN发送消息邮箱
CAN_msg       CAN_TxMsg;
// CAN message for receiving   
//CAN接收消息邮箱                       
CAN_msg       CAN_RxMsg;                                                          
// CAN HW ready to transmit a message
//发送就绪标志
unsigned int  CAN_TxRdy = 0;                      
// CAN HW received a message
//接收就绪标志
unsigned int  CAN_RxRdy = 0;                      

/*----------------------------------------------------------------------------
  setup CAN interface
 *----------------------------------------------------------------------------*/
void CAN_setup (void)  {
  unsigned int brp = stm32_GetPCLK1();

  RCC->APB1ENR |= RCC_APB1ENR_CANEN;              // enable clock for CAN

  // Note: uses PB8 and PB9 for CAN
  // enable clock for Alternate Function
  //启用复用功能的时钟
  RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;
  // reset CAN remap
  //复位CAN重新映射
  AFIO->MAPR   &= 0xFFFF9FFF;
  //   set CAN remap, use PB8, PB9
  //设置CAN重新映射，使用PB8，PB9
  AFIO->MAPR   |= 0x00004000; 
	// enable clock for GPIO B
	//使能GPIOB使用的RCC时钟										  
  RCC->APB2ENR |= RCC_APB2ENR_IOPBEN;
  // CAN RX pin PB.8 input push pull
  //PB.8推挽输入
  GPIOB->CRH &= ~(0x0F<<0);
  GPIOB->CRH |=  (0x08<<0);                        
  // CAN TX pin PB.9 alternate output push pull
  //PB.9复用推挽输出
  GPIOB->CRH &= ~(0x0F<<4);
  GPIOB->CRH |=  (0x0B<<4); 
  // enable interrupt
  //发送中断使能
  NVIC->ISER[0] |= (1 << (USB_HP_CAN_TX_IRQChannel  & 0x1F));
  // enable interrupt
  //接收中断使能
  NVIC->ISER[0] |= (1 << (USB_LP_CAN_RX0_IRQChannel & 0x1F));
  //初始化模式， 禁止报文自动重传
  CAN->MCR = (CAN_MCR_NART | CAN_MCR_INRQ);       // init mode, disable auto. retransmission
  // Note: only FIFO 0, transmit mailbox 0 used
  // FIFO 0 msg pending, Transmit mbx empty
  //FIFO0发生溢出的情况,FIFO 0的FOVR位被置’1’时，产生中断。
  //发送邮箱0变为空，RQCPx位被置’1’时，产生中断。
  CAN->IER = (CAN_IER_FMPIE0 | CAN_IER_TMEIE);    

  /* Note: this calculations fit for PCLK1 = 36MHz */
  //设置波特率
  brp  = (brp / 18) / 500000;                     // baudrate is set to 500k bit/s
                                                                          
  /* set BTR register so that sample point is at about 72% bit time from bit start */
  /* TSEG1 = 12, TSEG2 = 5, SJW = 4 => 1 CAN bit = 18 TQ, sample at 72%    */
  CAN->BTR &= ~(((        0x03) << 24) | ((        0x07) << 20) | ((         0x0F) << 16) | (          0x1FF)); 
  CAN->BTR |=  ((((4-1) & 0x03) << 24) | (((5-1) & 0x07) << 20) | (((12-1) & 0x0F) << 16) | ((brp-1) & 0x1FF));
}


/*----------------------------------------------------------------------------
  leave initialisation mode
 *----------------------------------------------------------------------------*/
void CAN_start (void)  {

  // normal operating mode, reset INRQ
  //使CAN从初始化模式进入正常工作模式
  CAN->MCR &= ~CAN_MCR_INRQ;                      
  while (CAN->MSR & CAN_MCR_INRQ);

}

/*----------------------------------------------------------------------------
  set the testmode
 *----------------------------------------------------------------------------*/
void CAN_testmode (unsigned int testmode) {

  // set testmode
  //设置CAN工作模式
  CAN->BTR &= ~(CAN_BTR_SILM | CAN_BTR_LBKM);     
  CAN->BTR |=  (testmode & (CAN_BTR_SILM | CAN_BTR_LBKM));
}

/*----------------------------------------------------------------------------
  check if transmit mailbox is empty
 *----------------------------------------------------------------------------*/
void CAN_waitReady (void)  {

  // Transmit mailbox 0 is empty
  //发送邮箱空？
  while ((CAN->TSR & CAN_TSR_TME0) == 0);
  CAN_TxRdy = 1;
 
}

/*----------------------------------------------------------------------------
  wite a message to CAN peripheral and transmit it
 *----------------------------------------------------------------------------*/
void CAN_wrMsg (CAN_msg *msg)  {

  // Reset TIR register
  //发送邮箱标识符寄存器复位
  CAN->sTxMailBox[0].TIR  = (unsigned int)0;      
  // Setup identifier information
  //如果是标准帧，标准帧是11位ID(报文识别码)
  if (msg->format == STANDARD_FORMAT)  
  {          //    Standard ID
      CAN->sTxMailBox[0].TIR |= (unsigned int)(msg->id << 21) | CAN_ID_STD;
  }  
  else//如果是扩展帧，扩展帧是29位ID(报文识别码)
  {                                      // Extended ID
      CAN->sTxMailBox[0].TIR |= (unsigned int)(msg->id <<  3) | CAN_ID_EXT;
  }
  // Setup type information
  //如果消息为数据帧
  if (msg->type == DATA_FRAME)  
  {                 // DATA FRAME
      CAN->sTxMailBox[0].TIR |= CAN_RTR_DATA;
  }
  else//数据为远程帧 
  {                                          // REMOTE FRAME
      CAN->sTxMailBox[0].TIR |= CAN_RTR_REMOTE;
  }
  //发送邮箱填充数据                                            // Setup data bytes
  CAN->sTxMailBox[0].TDLR = (((unsigned int)msg->data[3] << 24) | 
                             ((unsigned int)msg->data[2] << 16) |
                             ((unsigned int)msg->data[1] <<  8) | 
                             ((unsigned int)msg->data[0])        );
  CAN->sTxMailBox[0].TDHR = (((unsigned int)msg->data[7] << 24) | 
                             ((unsigned int)msg->data[6] << 16) |
                             ((unsigned int)msg->data[5] <<  8) |
                             ((unsigned int)msg->data[4])        );
  // Setup length
  //设置消息数据长度
  CAN->sTxMailBox[0].TDTR &= ~CAN_TDTxR_DLC;
  CAN->sTxMailBox[0].TDTR |=  (msg->len & CAN_TDTxR_DLC);
  // enable  TME interrupt
  //发送邮箱空中断使能
  CAN->IER |= CAN_IER_TMEIE;
  // transmit message
  //发送消息
  CAN->sTxMailBox[0].TIR |=  CAN_TIxR_TXRQ;       
}

/*----------------------------------------------------------------------------
  read a message from CAN peripheral and release it
 *----------------------------------------------------------------------------*/
void CAN_rdMsg (CAN_msg *msg)  {
  // Read identifier information
  //标识信息
  //如果是标准帧，标准帧是11位ID(报文识别码)
  if ((CAN->sFIFOMailBox[0].RIR & CAN_ID_EXT) == 0) 
  { // Standard ID
    msg->format = STANDARD_FORMAT;
    msg->id     = (u32)0x000007FF & (CAN->sFIFOMailBox[0].RIR >> 21);
  }  
  else//如果是扩展帧，扩展帧是29位ID(报文识别码)
  {                                          // Extended ID
    msg->format = EXTENDED_FORMAT;
    msg->id     = (u32)0x0003FFFF & (CAN->sFIFOMailBox[0].RIR >> 3);
  }
  // Read type information
  //如果消息为数据帧
  if ((CAN->sFIFOMailBox[0].RIR & CAN_RTR_REMOTE) == 0) 
  {
    msg->type =   DATA_FRAME;                     // DATA   FRAME
  }  
  else//数据为远程帧
  {
    msg->type = REMOTE_FRAME;                     // REMOTE FRAME
  }
  // Read length (number of received bytes)
  //消息数据长度
  msg->len = (unsigned char)0x0000000F & CAN->sFIFOMailBox[0].RDTR;
  // Read data bytes
  //从接收邮箱读数据
  msg->data[0] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDLR);
  msg->data[1] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDLR >> 8);
  msg->data[2] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDLR >> 16);
  msg->data[3] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDLR >> 24);

  msg->data[4] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDHR);
  msg->data[5] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDHR >> 8);
  msg->data[6] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDHR >> 16);
  msg->data[7] = (unsigned int)0x000000FF & (CAN->sFIFOMailBox[0].RDHR >> 24);

  // Release FIFO 0 output mailbox
  //释放接收FIFO 0输出邮箱，由于FIFO的特点，软件需要释放输出邮箱才能访问第2个报文
  CAN->RF0R |= CAN_RF0R_RFOM0;                    
}


void CAN_wrFilter (unsigned int id, unsigned char format)  {
  static unsigned short CAN_filterIdx = 0;
         unsigned int   CAN_msgId     = 0;
  // check if Filter Memory is full
  //检查CAN过滤器是否已满
  if (CAN_filterIdx > 13) 
  {                       
    return;
  }
  // Setup identifier information
  //如果是标准帧，标准帧是11位ID(报文识别码)
  if (format == STANDARD_FORMAT)  
  {               // Standard ID
      CAN_msgId  |= (unsigned int)(id << 21) | CAN_ID_STD;
  }  
  else//如果是扩展帧，扩展帧是29位ID(报文识别码)
  {                                      // Extended ID
      CAN_msgId  |= (unsigned int)(id <<  3) | CAN_ID_EXT;
  }
  // set Initialisation mode for filter banks
  //CAN过滤器组工作在初始化模式
  CAN->FMR  |=  CAN_FMR_FINIT;  
  // deactivate filter                  
  CAN->FA1R &=  ~(unsigned int)(1 << CAN_filterIdx); 

  // initialize filter
  // set 32-bit scale configuration 
  //初始化过滤器
  //过滤器位宽为单个32位
  CAN->FS1R |= (unsigned int)(1 << CAN_filterIdx);
  // set 2 32-bit identifier list mode
  //过滤器组x的2个32位寄存器工作在标识符列表模式
  CAN->FM1R |= (unsigned int)(1 << CAN_filterIdx);
  //  32-bit identifier
  //32位标识符
  CAN->sFilterRegister[CAN_filterIdx].FR1 = CAN_msgId; 
  //  32-bit identifier
  //32位标识符
  CAN->sFilterRegister[CAN_filterIdx].FR2 = CAN_msgId; 
  // assign filter to FIFO 0
  //过滤器被关联到FIFO0
  CAN->FFA1R &= ~(unsigned int)(1 << CAN_filterIdx);  
  // activate filter
  //过滤器被激活
  CAN->FA1R  |=  (unsigned int)(1 << CAN_filterIdx);  
  // reset Initialisation mode for filter banks
  //CAN过滤器组工作在正常模式
  CAN->FMR &= ~CAN_FMR_FINIT;                     
  // increase filter index
  //设置的过滤器数量增加
  CAN_filterIdx += 1;
}

/*----------------------------------------------------------------------------
  CAN transmit interrupt handler
  CAN发送中断
 *----------------------------------------------------------------------------*/
void USB_HP_CAN_TX_IRQHandler (void) {
  // request completed mbx 0
  //邮箱0请求完成
  if (CAN->TSR & CAN_TSR_RQCP0) 
  { 
  	// reset request complete mbx 0
  	//复位邮箱0请求
    CAN->TSR |= CAN_TSR_RQCP0;
    // disable  TME interrupt 
    //禁止发送邮箱空中断                   
    CAN->IER &= ~CAN_IER_TMEIE;                   
	
	  CAN_TxRdy = 1; 
  }
}

/*----------------------------------------------------------------------------
  CAN receive interrupt handler
  CAN接收中断
 *----------------------------------------------------------------------------*/
void USB_LP_CAN_RX0_IRQHandler (void) {
  // message pending ?
  //接收到CAN报文，通过判断报文数目判断是否有报文
  if (CAN->RF0R & CAN_RF0R_FMP0) 
  {			     
	  // read the message
	  //接收报文
	  CAN_rdMsg (&CAN_RxMsg); 

    CAN_RxRdy = 1;// set receive flag
  }
}