Code for example CAN bus receiver.

can_reciever.ino

// demo: CAN-BUS Shield, receive data
#include "mcp_can.h"
#include <SPI.h>
#include <LiquidCrystal.h>
#include <stdio.h>
#define INT8U unsigned char

INT8U Flag_Recv = 0;
INT8U len = 0;
INT8U buf[8];
INT32U canId = 0x000;
char str[20];
LiquidCrystal lcd(9, 8, 7, 6, 5, 4);

void setup()
{
  lcd.begin(20, 4);
  CAN.begin(CAN_100KBPS);                   // init can bus : baudrate = 100k
  attachInterrupt(0, MCP2515_ISR, FALLING); // start interrupt
  Serial.begin(115200);
}

void MCP2515_ISR()
{
     Flag_Recv = 1;
}

void loop()
{
    if(Flag_Recv)                   // check if data was recieved
    {
      Flag_Recv = 0;                // clear flag
      CAN.readMsgBuf(&len, buf);    // read data,  len: data length, buf: data buf
      canId = CAN.getCanId();
      //Print data to the serial console 
      //and the LCD display
      Serial.println("CAN_BUS GET DATA!");
      Serial.print("CAN ID: ");
      Serial.println(canId);
      lcd.setCursor(0, 0);
      lcd.print("CAN ID: ");
      lcd.print(canId);
      lcd.setCursor(0, 2);
      Serial.print("data len = ");Serial.println(len);
      //This loops through each byte of data and prints it
      for(int i = 0; i<len; i++)    // print the data
      {
        Serial.print(buf[i]);Serial.print("\t");
        lcd.print(buf[i]);
        lcd.print(" ");
      }
      Serial.println();
      delay(50);
    }
}

but during compilation error occurred
it say that INT32U does not name a type

6: error: 'INT32U' does not name a type

INT32U canId = 0x000;

Tengo el mismo error y no se que podra ser.