# Raspberry Pi CM4 HAT

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The board is designed for connecting CAN bus to Raspberry Pi. It gives access to Cyphal (opens new window)/DroneCAN (opens new window) (old name UAVCAN)

# 1. General

# 1.1. Variations

There are two connection options.

RPI CM4 RPI4 Common

# 1.2. Main function

# 2. Hardware specification

# 2.1. Features

  • CAN to RPI-SPI - MCP2515-I/ST
  • FDCAN to RPI_SPI - MCP2517FD-H/SL
  • FT1 - RPI_SDCARD

# 2.2. Wire

Connectors

Name Description
1 CAN1, CAN2 First CAN port
2 CAN3, CAN4 Second CAN port
3 SWD Serial wire debug from RPI to STM
4 DEBUG SWD
5 STM-USB
6 XT30PW-M Power input
7 IR1 InfraRed UART RX/TX
8 SERIAL1 RPI ttyS0
9 J8,J9 Bottom connector slot
10 RPI1 RPI4 header
11 J1,J2 Compute Module 4 headers
12 RPI-USB RPI USB Type-C
13 FT1 SD CARD to extend memory of RPI
14 J5 Ethernet RJ45 connected to RPI

Pin configuration and functions

Pin configuration for RPI

GPIO Defedition
GPIO25 SWCLK
GPIO24 SWDIO
GPIO18 Green led
GPIO15 PI_RXI - STM_TX
GPIO14 PI_TXO - STM_RX
GPIO10 MCP2515_MOSI
GPIO9 MCP2515_MISO
GPIO11 MCP2515_SCK
GPIO8 MCP2515_nCS
GPIO7 MCP2515_nCS

RPI UART map (opens new window)

TXD RXD CTS RTS Board Pins
uart0 14 15 8 10
uart1 14 15 8 10
uart2 0 1 2 3 27 28 (I2C)
uart3 4 5 6 7 7 29
uart4 8 9 10 11 24 21 (SPI0)
uart5 12 13 14 15 32 33 (gpio-fan)

# 2.3. Specifications

Mechanical

drw

Width, mm Length, mm Height, mm
Outline
PCB

Total weight of device is 6.6 g.

You can download 3D model on GrabCAD (opens new window)

Housing

Information about case presented here.

Absolute Maximum Ratings

Parameter MIN MAX UNIT
Vin (CAN1) 5.5 55* V
V (CAN2, CAN3) 4.5 5.5 V
I max A
Operating temperature

*Noted Voltage should be delivered only with current limitation under 2.5 Amp.

Recommended operating conditions

Parameter Value UNIT
Vin (CAN3) 30 V
V (CAN1, CAN2) 5 V
I max A

ESD ratings

Description Value UNIT
Human-body model (HBM) 2000 V
Charged-device model (CDM) 500 V

# 2.4. Description

Functional Block Diagram

Connection example diagram

# 2.5. Power Supply Recommendations

Device is designed to operate from an input voltage supply range between 4.5 V and 5.5 V over CAN2 or CAN3 connector, or 5.5 - 30 V from CAN1. This input supply must be able to withstand the maximum input current and maintain a stable voltage. The resistance of the input supply rail should be low enough that an input current transient does not cause a high enough drop that can cause a false UVLO fault triggering and system reset. The amount of bulk capacitance is not critical, but a 47-μF or 100-μF electrolytic capacitor is a typical choice.

# 2. Led indication

  • LED1
  • PI_LED_nPWR - RED
  • GPIO18 - GREEN
  • PI_nLED_Activity - BLUE

# Inspired by

# 2.6. Revision history

version Description
v