High-reliability new energy industry top self-media

Engineers in embedded systems generally know that the CAN bus is widely used in automobiles. In fact, ship electronic devices also widely use CAN. As the country pays more and more attention to maritime defense, the demand for CAN will also increase.

Physical Layer

CRC Error: This error occurs when the sent and received CRC values differ;

Format Error: This error occurs when the frame format is invalid;

Acknowledgment Error: This error occurs when the sending node does not receive acknowledgment during the ACK phase;

Bit Sending Error: This error occurs when the sending node detects that the bus level does not match the sending level during transmission;

Bit Stuffing Error: This error occurs when the communication line violates communication rules.

#define REG_BASE_ADDR 0xA000 // Register base address

unsigned char *SJA_CS_Point = (unsigned char *) REG_BASE_ADDR ;

// Write to SJA1000 register
void WriteSJAReg(unsigned char RegAddr, unsigned char Value) 
{
    *(SJA_CS_Point + RegAddr) = Value;
    return;
}

// Read from SJA1000 register
unsigned char ReadSJAReg(unsigned char RegAddr) 
{
    return (*(SJA_CS_Point + RegAddr));
}

…… 
for (i=0; i<len; i++) 
{
    WriteSJAReg(RegAdr + i, ValueBuf[i]);
}
……

…… 
for (i=0; i<len; i++) 
{
    ReadSJAReg(RegAdr + i, ValueBuf[i]);
}
……

#ifndef __CONFIG_H__ // Prevent header file from being included multiple times
#define __CONFIG_H__
#include <8051.h>         // Include 80C51 register definition header file
#include "SJA1000REG.h"         // Include SJA1000 register definition header file
// Define byte operations
#define LOW_BYTE(x)  (unsigned char)(x)
#define HIGH_BYTE(x)  (unsigned char)((unsigned int)(x) >> 8)
// Define oscillator clock and processor clock frequency (users can adjust according to actual conditions)
#define OSCCLK 11059200UL
// Macro definition of MCU clock frequency
#define CPUCLK (OSCCLK / 12)
#endif // __CONFIG_H__

char SetSJASendCmd(unsigned char cmd) 
{ 
    unsigned char ret;  
    switch (cmd) 
    {  
        default:  
        case 0:  
            ret = SetBitMask(REG_CAN_CMR, TR_BIT); // Normal send  
            break;     
        case 1:  
            ret = SetBitMask(REG_CAN_CMR, TR_BIT|AT_BIT); // Single send 
            break;
        case 2: 
            ret = SetBitMask(REG_CAN_CMR, TR_BIT|SRR_BIT);// Self-send  
            break; 
        case 0xff:  
            ret = SetBitMask(REG_CAN_CMR, AT_BIT);// Terminate send  
            break; 
    } 
    return ret;
}

unsigned char SJA_CAN_Filter[8] = 
{    
    // Define acceptance filter parameters, receive all frames       
    0x00, 0x00, 0x00, 0x00,                                                 
    // ACR0~ACR3       
    0xff, 0xff, 0xff, 0xff                                                         
    // AMR0~AMR3
};

unsigned char STD_SEND_BUFFER[11] = 
{   
    // CAN send message buffer       
    0x08,             // Frame information, standard data frame, data length = 8       
    0xEA, 0x60,   // Frame ID = 0x753
    0x55, 0x55, 0x55, 0x55, 0xaa, 0xaa, 0xaa, 0xaa  // Frame data
};

void main(void) // Main function, program entry
{        
    timerInit();// Initialize
    D1 = 0;        
    SJA1000_RST = 1; // Hardware reset SJA1000       
    timerDelay(50); // Delay 500ms       
    SJA1000_RST = 0;       
    SJA1000_Init(0x00, 0x14, SJA_CAN_Filter);   // Initialize SJA1000, set baud rate to 1Mbps       
    // Infinite loop, main() function is not allowed to return      
    for(;;) 
    {           
        SJASendData(STD_SEND_BUFFER, 0x0);           
        timerDelay(100);         // Delay 1000ms      
    }    
}