Getting Started What is CAN bus? Controller Area Network (CAN) is a serial communication protocol that lets microcontrollers and devices talk to each other without a central host computer. Developed by Bosch in the 1980s, it is now the standard in automotive and heavy vehicle electronics. Why buses use it In a MAN Lion's City , dozens of ECUs (Electronic Control Units) share data in real time: the engine tells the instrument cluster the RPM, the EBS reports brake air pressure, the tachograph transmits vehicle speed — all over two wires (CAN_H and CAN_L). The J1939 standard Heavy vehicles (buses, trucks) use SAE J1939 , an application layer built on top of CAN. It defines: Element Description 29-bit ID Extended identifier (vs 11-bit basic CAN) PGN Parameter Group Number — identifies the data type SA Source Address — address of the sending ECU (0x00–0xFE) SPN Suspect Parameter Number — each signal within a PGN Implementation parameters Parameter Value Bus speed 250 kbps ID type Extended (29-bit) Send cycle 20 ms (50 Hz) Transceiver MCP2515 + TJA1050 MCP2515 oscillator 8 MHz Note 0xFF bytes in unused positions are the J1939 default for "parameter not available" (SNA — Specific Not Available). Hardware setup Compatible boards Any Arduino with SPI support works. The CS pin and SPI pins vary by board: Board SCK MOSI MISO CS (recommended) Notes Arduino Mega 2560 52 51 50 53 Hardware SPI, most headroom Arduino Uno 13 11 12 10 5V, limited RAM Arduino Nano 13 11 12 10 Same as Uno, compact Arduino Micro 15 16 14 10 5V, USB HID capable Arduino Leonardo 15 16 14 10 Same as Micro ESP32 18 23 19 5 3.3V — use level shifter For ESP32, the MCP2515 runs at 3.3V — do not connect directly to a 5V MCP2515 module without a level shifter. Required components Component Recommended model Microcontroller Any board from the table above CAN module MCP2515 + TJA1050 breakout board Bus terminators 2× 120 Ω resistor Wiring Twisted pair for CAN_H / CAN_L Wiring — Arduino Mega Arduino Mega MCP2515 module 5V VCC GND GND pin 52 SCK pin 51 MOSI pin 50 MISO pin 53 CS pin 2 INT (optional) Wiring — Arduino Uno / Nano Arduino Uno/Nano MCP2515 module 5V VCC GND GND pin 13 SCK pin 11 MOSI pin 12 MISO pin 10 CS pin 2 INT (optional) Initialization code Change SPI_CS_PIN to match your board: #include #include const int SPI_CS_PIN = 10; // 53 for Mega, 10 for Uno/Nano MCP_CAN CAN(SPI_CS_PIN); void setup() { while (CAN_OK != CAN.begin(MCP_ANY, CAN_250KBPS, MCP_8MHZ)) { delay(100); } CAN.setMode(MCP_NORMAL); } MCP2515 oscillator Most MCP2515 modules come with an 8 MHz crystal. Some come with 16 MHz — check the crystal printed on your module and change the parameter accordingly: Crystal Parameter 8 MHz MCP_8MHZ 16 MHz MCP_16MHZ Installing the library Install mcp_can by Cory Fowler from the Arduino IDE library manager, or clone directly: cd ~/Documents/Arduino/libraries git clone https://github.com/coryjfowler/MCP_CAN_lib Important Always place a 120 Ω resistor between CAN_H and CAN_L at each end of the bus. Without terminators, signal reflections will make the bus unstable.