Hardware:

CAN Shield

The following is the block diagram for out CAN-BUS Expansion board, wired up as shown:

Note: under the MCP2515 board there is a solder jumper to enable 120R termination resistance

In a CAN bus network, where you are using multiple MCP2551 transceivers (or other CAN transceivers), you need exactly two 120-ohm termination resistors.

Reason:

• The 120-ohm resistors are used to terminate the CAN bus to prevent signal reflections, ensuring reliable communication.
• These termination resistors should be placed at both ends of the CAN bus to match the characteristic impedance of the bus, which is typically 120 ohms.

Key Points:

• No matter how many MCP2551 transceivers or nodes are on the bus, you only need two 120-ohm resistors.
• The resistors should be placed at the two furthest points on the bus, not at every node.

Example:

If you have many nodes (say, 5 or 10 MCP2551 modules) connected to a single CAN bus, you still only need two 120-ohm resistors at the ends of the bus.

So, regardless of the number of modules, always ensure that there are two 120-ohm termination resistors on the CAN bus.

Software Usage:

Library Installation

Initialization

To create connection with MCP2515 provide pin number where SPI CS is connected (10 by default), baudrate and mode