can1.c

51系列单片机CAN多点通信C语言源代码

  OSCXCN  = 0x77;               // start external oscillator; 22.1184 MHz Crystal
                                // system clock is 22.1 MHz / 2(二分频) = 11.0592 MHz
                                // 0111 0111 书150页
  for (n=0;n<255;n++);          // delay about 1ms
  while ((OSCXCN & 0x80) == 0); // wait for oscillator to stabilize

  CLKSEL |= 0x01;               // switch to external oscillator 系统时钟采用外部时钟
}

void config_IO (void)
{
  SFRPAGE  = CONFIG_PAGE;        //Port SFR's on Configuration page

  XBR3     = 0x80;     // Configure CAN TX pin (CTX) as push-pull digital output
                       // BIT7=1: CTX配为推挽模式

  P1MDOUT |= 0x40;     // Configure P1.6 as push-pull to drive LED
                       // 1：相应口设为推挽输出模式

  XBR2     = 0x40;     // Enable Crossbar/low ports
//bit6=1,Crossbar开启，交叉配置时将XBARE清0,配置结束后将其置1,使交叉开关生效
}

////////////////////////////////////////////////////////////////////////////////
//CAN Functions
////////////////////////////////////////////////////////////////////////////////

//Clear Message Objects
void clear_msg_objects (void)   //将所有消息清0
{
  SFRPAGE  = CAN0_PAGE;
  CAN0ADR  = IF1CMDMSK;    // Point to  IF1 Command Mask Register 1
  CAN0DATL = 0xFF;         // Set direction to WRITE all IF registers to Msg Obj
  for (i=1;i<33;i++)       //  i 为1到32
    {
      CAN0ADR = IF1CMDRQST; // Write blank (reset) IF registers to each msg obj
      CAN0DATL = i;
    }
}

//Initialize Message Object for RX
void init_msg_object_RX (char MsgNum) //初始化消息对象接收消息号为0x01
{
  SFRPAGE  = CAN0_PAGE;
  CAN0ADR  = IF1CMDMSK;  // Point to Command Mask 1
  CAN0DAT  = 0x00B8;     // Set to WRITE, and alter all Msg Obj except ID MASK
//0000 0000 1011 1000    // and data bits

  CAN0ADR  = IF1ARB1;    // Point to arbitration1 register
  CAN0DAT  = 0x0000;     // Set arbitration1 ID to "0"

  CAN0DAT  = 0x8004;     // Arb2 high byte:Set MsgVal bit, no extended ID,
//1000 0000 0000 0100    // Dir = RECEIVE

  CAN0DAT  = 0x0480;     // Msg Cntrl: set RXIE, remote frame function disabled(因为RmtEn=0)
//0000 0100 1000 0000

  CAN0ADR  = IF1CMDRQST; // Point to Command Request reg.
  CAN0DATL = MsgNum;     // Select Msg Obj passed into function parameter list
                         // --initiates write to Msg Obj
						 // MsgNum为消息号，即1~~32
  // 3-6 CAN clock cycles to move IF register contents to the Msg Obj in CAN RAM
}

//Initialize Message Object for TX
void init_msg_object_TX (char MsgNum)
{
  SFRPAGE = CAN0_PAGE;  //切换到CAN寄存器页
  CAN0ADR = IF1CMDMSK;  // （指向）Point to Command Mask 1 寄存器
  CAN0DAT = 0x00B2;     // Set to WRITE, & alter all Msg Obj except ID MASK bits
                        // 设定读写方向（写），改变所有信息目标但MASK位不变
  CAN0ADR = IF1ARB1;    // Point to arbitration1 register
  CAN0DAT = 0x0000;     // Set arbitration1 ID to highest priority
                        // 写仲裁寄存器，设定信息ID（标志码）

  //CAN0ADR = IF1ARB2   // CAN0ADR会自动加0,所以这一行要不要都可以
  CAN0DAT = 0xA000;     // Autoincrement to Arb2 high byte:
                        // Set MsgVal bit, no extended ID即不扩展ID, Dir = WRITE 即报文传输方向为发送
                        // 设定信息目标有效位并设为标准帧，读写方向为WRITE

  //CAN0ADR = IF1MSGC   // IF1 Message Control   Register     CAN0ADR会自动加0,所以这一行要不要都可以
  CAN0DAT = 0x0081;     // Msg Cntrl: DLC = 1, remote frame function not enabled（远程帧功能未启用）
                        // EoB=1 当消息对象只是应用与单数据帧场合，则此位须置1,书213页
                        // 数据帧的数据长度为1个字节（DLC = 1）

  CAN0ADR = IF1CMDRQST; // Point to Command Request reg.
  CAN0DAT = MsgNum;     // 选择信息目标号 Select Msg Obj passed into function parameter list
                        // --initiates write to Msg Obj
                        // MsgNum 为1到32消息号

  // 3-6 CAN clock cycles to move IF reg contents to the Msg Obj in CAN RAM.
}

//Start CAN
void start_CAN (void)
{
  /* Calculation of the CAN bit timing :

  System clock        f_sys = 22.1184 MHz/2 = 11.0592 MHz.
  System clock period t_sys = 1/f_sys = 90.422454 ns.
  CAN time quantum       tq = t_sys (at BRP = 0)

  Desired bit rate is 1 MBit/s, desired bit time is 1000 ns.
  Actual bit time = 11 tq = 996.65ns ~ 1000 ns
  Actual bit rate is 1.005381818 MBit/s = Desired bit rate+0.5381%

  CAN bus length = 10 m, with 5 ns/m signal delay time.
  Propagation delay time : 2*(transceiver loop delay + bus line delay) = 400 ns
  (maximum loop delay between CAN nodes)

  Prop_Seg = 5 tq = 452 ns ( >= 400 ns).
  Sync_Seg = 1 tq

  Phase_seg1 + Phase_Seg2 = (11-6) tq = 5 tq
  Phase_seg1 <= Phase_Seg2,  =>  Phase_seg1 = 2 tq and Phase_Seg2 = 3 tq
  SJW = (min(Phase_Seg1, 4) tq = 2 tq

  TSEG1 = (Prop_Seg + Phase_Seg1 - 1) = 6
  TSEG2 = (Phase_Seg2 - 1)            = 2
  SJW_p = (SJW - 1)                   = 1

  Bit Timing Register = BRP + SJW_p*0x0040 = TSEG1*0x0100 + TSEG2*0x1000 = 2640

  Clock tolerance df :

  A: df < min(Phase_Seg1, Phase_Seg2) / (2 * (13*bit_time - Phase_Seg2))
  B: df < SJW / (20 * bit_time)

  A: df < 2/(2*(13*11-3)) = 1/(141-3) = 1/138 = 0.7246%
  B: df < 2/(20*11)                   = 1/110 = 0.9091%

  Actual clock tolerance is 0.7246% - 0.5381% = 0.1865% (no problem for quartz)
  */

  SFRPAGE  = CAN0_PAGE;
  CAN0CN  |= 0x41;       // 将 CCE and INIT 位置1,开始初始化
 // 0100 0001 CCE=1,若CPU要对CAN波特率重新配置，该位必须为1,且Init位也必须为1
 //           Init=1,CAN正常操作挂起，CPU要对CAN控制器初始化配置时应将此位先置1

  CAN0ADR  = BITREG;     // 指向定时寄存器进行配置 Point to Bit Timing register
  CAN0DAT  = 0x2640;     // see above  配置波特率
// 0010 0110 0100 0000 
// TSeg2=bit14~bit12=010,采样点之前的位时间片断
// TSeg1=bit11~bit8=0110,采样点之后的位时间片断
// SJW=bit7~bit6=01,同步跳转宽度，可设置为0x0~0x3，即0~3
// BRP=bit5~bit0,时间份额设置

  CAN0ADR  = IF1CMDMSK;  // Point to Command Mask 1
  CAN0DAT  = 0x0087;     // Config for TX : WRITE to CAN RAM, write data bytes,
                         // set TXrqst/NewDat, clr IntPnd

  // RX-IF2 operation may interrupt TX-IF1 operation
  CAN0ADR  = IF2CMDMSK;  // Point to Command Mask 2
  CAN0DATL = 0x1F;       // Config for RX : READ CAN RAM, read data bytes,
                         // clr NewDat and IntPnd
  CAN0CN  |= 0x06;       // 允许全局中断 Global Int. Enable IE and SIE
  CAN0CN  &= ~0x41;      // Clear CCE and INIT bits, starts CAN state machine
}

//Transmit CAN frame to turn other node's LED ON
void transmit_turn_LED_ON (char MsgNum)
{
  SFRPAGE  = CAN0_PAGE;  // IF1 already set up for TX
  CAN0ADR  = IF1CMDMSK;  // Point to Command Mask 1
  CAN0DAT  = 0x0087;     // Config to WRITE to CAN RAM, write data bytes,
                         // set TXrqst/NewDat, Clr IntPnd
  CAN0ADR  = IF1DATA1;   // 指向数据场的第一个字节 Point to 1st byte of Data Field
  CAN0DATL = 0x11;       // Ones signals to turn LED's light ON in data A1 field
  CAN0ADR  = IF1CMDRQST; // Point to Command Request Reg.
  CAN0DATL = MsgNum;     // 将报文对象编号写入，则数据发送到对应的报文对象中
                         // Move new data for TX to Msg Obj "MsgNum"
}

//Transmit CAN Frame to turn other node's LED OFF
void transmit_turn_LED_OFF (char MsgNum)
{
  SFRPAGE  = CAN0_PAGE;  // IF1 already set up for TX
  CAN0ADR  = IF1DATA1;   // Point to 1st byte of Data Field
  CAN0DATL = 0x00;       // Zero signals to turn LED's light ON in Data A1 field
  CAN0ADR  = IF1CMDRQST; // Point to Command Request Reg.
  CAN0DATL = MsgNum;     // Move new data for TX to Msg Obj "MsgNum"
}


// Receive Data from the IF2 buffer
void receive_data (char MsgNum)
{
  char virtual_button;
  SFRPAGE  = CAN0_PAGE; // IF1 already set up for RX
  CAN0ADR  = IF2CMDRQST;// Point to Command Request Reg.
  CAN0DATL = MsgNum;    // Move new data for RX from Msg Obj "MsgNum"
                        // Move new data to a
  CAN0ADR  = IF2DATA1;  // Point to 1st byte of Data Field

  virtual_button = CAN0DATL;
  if (virtual_button == 0x11)   //Ones is signal from other node to turn LED ON
    LED = 1; //sbit LED = P1^6;
  else  LED = 0;                //Otherwise turn LED OFF (message was one's)
}

////////////////////////////////////////////////////////////////////////////////
//Interrupt Service Routine
////////////////////////////////////////////////////////////////////////////////
void ISRname (void) interrupt 19
{
  status = CAN0STA; 
//CAN控制寄存器（CAN0CN）、CAN状态寄存器（CAN0STA）、CAN测试寄存器（CANTST）

  if ((status&0x10) != 0)
    {                            // RxOk is set, interrupt caused by reception
      CAN0STA = (CAN0STA&0xEF)|0x07;         // Reset RxOk, set LEC to NoChange
      /* read message number from CAN INTREG */
      receive_data (0x01);             // Up to now, we have only one RX message
    }
  if ((status&0x08) != 0)
    {                            // TxOk is set, interrupt caused by transmision
      CAN0STA = (CAN0STA&0xF7)|0x07;        // Reset TxOk, set LEC to NoChange
    }
  if (((status&0x07) != 0)&&((status&0x07) != 7))
    {                           // Error interrupt, LEC changed
      /* error handling ? */
      CAN0STA = CAN0STA|0x07;              // Set LEC to NoChange
    }
}