Designed to easily allow the addition of a CAN (Controller Area Network) node interface to any process control or data acquisition application these CAN Nodes utilise the Microchip MC2551 high speed CAN transceiver to interface with a CAN bus.  Suitable for 12 or 24V bus systems they support 1Mb/s and up to 112 connected nodes and implement the ISO-11898 standard physical layer requirements.

Can Node 1 includes the MCP2515 standalone CAN controller which implements the CAN specification version 2.0B. It handles all transmit and receive protocols and interfaces via an SPI interface with the onboard PIC16F675 microcontroller. The MCP2515 provides the option of 3 digital inputs and two digital outputs. An onboard 3 way dip switch can also be linked to the three MCP2515 inputs. The PIC16F675 adds two more I/O connections, which can be set as 10bit analogue inputs.

Can Node 2 includes the MCP25050 CAN I/O expander which provides up to 8 digital I/O, up to 4 10-bit A/D converters and up to 2 PWM outputs configurable by user via an ICSP header.

On both nodes, all available I/Os are accessable via a rising clamp screw terminal block, as are the CAN bus connections and power supply inputs. Normally powered by 5V DC, an onboard 5V regulator allows use of a higher voltage.

Software examples and general CAN application information are available from the Microchip website

Controller Area Network (CAN) is a multicast shared serial bus standard, originally developed in the 1980s by Robert Bosch GmbH, for connecting electronic control units (ECUs). CAN was specifically designed to be robust in electromagnetically noisy environments and can utilize a differential balanced line like RS-485. It can be even more robust against noise if twisted pair wire is used. Although initially created for automotive purposes (as a vehicle bus), nowadays it is used in many embedded control applications (e.g., industrial) that may be subject to noise.

Bit rates up to 1 Mbit/s are possible at networks length below 40 m. Decreasing the bit rate allows longer network distances (e.g. 125 kbit/s at 500 m).

The CAN data link layer protocol is standardized in ISO 11898-1 (2003). This standard describes mainly the data link layer — composed of the Logical Link Control (LLC) sublayer and the Media Access Control (MAC) sublayer — and some aspects of the physical layer of the ISO/OSI Reference Model. All the other protocol layers are left to the network designer's choice.

(**) Taken from Wikepedia