Eight Serial Ports HAT 2-Layer Stackable for Raspberry Pi

Overview

Compatible with all Raspberry Pi models from the Raspberry Pi 3 to Raspberry Pi 5, the Eight Serial Ports HAT provides a compact and versatile solution for connecting your Raspberry Pi to virtually any industrial serial device. The card supports six of the most widely used industrial communication standards, including three RS-232 ports, one RS-485 port, one RS-422 port, one CAN port, one 1-Wire port, and one M-BUS port.

The HAT uses the Raspberry Pi's native UART interfaces together with two onboard 32-bit ARM Cortex processors to implement all communication ports without requiring additional hardware. This architecture provides a complete industrial communication platform while preserving compatibility with standard Linux drivers and applications.

• Three RS232, one RS485, one RS422, one CAN, one 1-Wire, and one M-BUS port on a single board
• RS232, RS485, RS422, M-BUS, and CAN ports use standard Linux kernel drivers — no additional software required
• Selectable termination on the RS485, RS422, and CAN ports via the onboard DIP switch
• Two Level Stackable, for up to 16 serial ports on one Raspberry Pi
• On board hardware watchdog and reset pushbutton
• Status LED indicator on each serial port and power
• Compatible with all Raspberry Pi versions from 3 to 5
• ECCN Code EAR99

INTERFACES AND I/O

DESCRIPTION

The Eight Serial Ports HAT gives Raspberry Pi a complete set of industrial serial interfaces on a single, compact, stackable board.

The latest Raspberry Pi models expose up to four UART-capable ports on the GPIO header, but none of them work without a physical layer transceiver. The Eight Serial Ports HAT uses all four of these ports, plus eight additional ports generated by two 32-bit ARM Cortex processors, to implement all the common serial interfaces in use today. The two processors communicate with the Raspberry Pi over I2C, with the hardware address selected by the onboard DIP switch. A status LED next to each port lights up when that port is active.

TECHNICAL DETAILS

CARD LAYOUT

MECHANICAL SPECIFICATIONS

DIP SWITCH AND STACKING

The onboard DIP switch sets the card's stack address and configures termination on the RS485, RS422, and CAN ports.

Two Eight Serial Ports HATs can be stacked on one Raspberry Pi for a total of 16 serial ports. However, the Linux kernel exposes at most 8 ttySCx devices at a time, so not all 16 UART ports generated by two stacked cards can be used simultaneously through the standard kernel driver — the remaining ports require a custom driver.

ELECTRICAL SPECIFICATIONS

POWER REQUIREMENTS

COMMUNICATION INTERFACES

HARDWARE WATCHDOG

The Eight Serial Ports HAT includes a hardware watchdog that ensures your system automatically recovers if the Raspberry Pi software becomes unresponsive. The watchdog is disabled at power-up and activates after it receives the first reset command from the Raspberry Pi.

For a full list of watchdog commands, run: 8serial -h

COMPATIBILITY

FIRMWARE UPDATE

The Eight Serial Ports HAT contains two onboard microcontrollers, both of which can be updated in the field. The update tool downloads the latest firmware from Sequent Microsystems' servers and flashes it to the board over I2C.

Running the Update

~$ cd ~/8serial-rpi/update/

~/8serial-rpi/update$ ./update <id> 1 — updates the first onboard CPU

~/8serial-rpi/update$ ./update <id> 2 — updates the second onboard CPU

Replace <id> with the board stack address (0-1). Full instructions including recovery procedures are available at:

https://github.com/SequentMicrosystems/8serial-rpi/tree/main/update/README.md

DOWNLOADS

WHAT'S INCLUDED

When you purchase the card you will receive the following items:

1. Eight Serial Ports HAT for Raspberry Pi

2. Mounting Hardware
	Four M2.5×18mm male-female brass standoffs Four M2.5×5mm brass screws Four M2.5 brass nuts

3. Connector Plugs

QUICK START

1. Plug your card on top of your Raspberry Pi and power up the system.
2. Enable I2C communication on Raspberry Pi using raspi-config.
3. Edit /boot/config.txt (or /boot/firmware/config.txt on newer Raspbians), adding the dtoverlay lines for the card's stack ID, as documented in the README.
4. Reboot, then run ls /dev to confirm the ttySCx serial ports are present, and dmesg | grep can0 to confirm the CAN port is up.
5. To use the hardware watchdog, 1-Wire bus, and reset pushbutton, install the 8serial command line from GitHub:
   ~$ git clone https://github.com/SequentMicrosystems/8serial-rpi.git

   ~$ cd /home/pi/8serial-rpi

   ~/8serial-rpi$ sudo make install

   ~/8serial-rpi$ 8serial -h

The program will respond with a list of available commands. To read more about the cli, please refer to the README file.