Pinout & Interfaces

The RS485 CAN HAT connects to the Raspberry Pi through the standard 40-pin GPIO header, using SPI for CAN bus communication and UART for RS-485. This page documents every signal the HAT uses and the terminal block pinout for field wiring.

CAN Bus Pins

The CAN interface is driven by the MCP2515 controller over SPI, with an interrupt line on GPIO 25.

Function	Raspberry Pi (BCM)	Description
3V3	3V3	3.3V Power Input
GND	GND	Ground
SCK	SCK	SPI Clock Input
MOSI	MOSI	SPI Data Input
MISO	MISO	SPI Data Output
CS	CE0	Chip Select
INT	GPIO 25	Interrupt Output

RS-485 Pins

The RS-485 interface uses the Pi’s UART and, optionally, a direction-control GPIO.

Function	Raspberry Pi (BCM)	Description
3V3	3V3	3.3V Power Input
GND	GND	Ground
RXD	RXD	UART Receive
TXD	TXD	UART Transmit
RSE	GPIO 4	TX/RX Direction Control

RSE is optional

The factory default uses hardware automatic TX/RX switching, so the RSE pin does not need to be connected unless you want manual software control of the transceiver direction. Leave it disconnected for the simplest setup.

Terminal Blocks

The board exposes two screw-terminal blocks on the edge for field wiring.

CAN Terminal

Terminal	Signal
H	CAN High
L	CAN Low

RS-485 Terminal

Terminal	Signal
A	Non-inverting (D+)
B	Inverting (D-)

Caution

When connecting CAN bus wiring, always match H to H and L to L between nodes. For RS-485, match A to A and B to B. Reversing a differential pair will prevent communication entirely.