Home » Four Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi
Four Serial Ports RS232-RS485 for Raspberry Pi - top view
Four Serial Ports RS232-RS485 for Raspberry Pi - side 1
Four Serial Ports RS232-RS485 for Raspberry Pi - side 2
Four Serial Ports RS232-RS485 for Raspberry Pi - side 3
Four Serial Ports RS232-RS485 for Raspberry Pi - side 4
Four Serial Ports RS232-RS485 for Raspberry Pi - back view
Four Serial Ports RS232-RS485 for Raspberry Pi - 360 view
Four Serial Ports RS232-RS485 for Raspberry Pi - top view
Four Serial Ports RS232-RS485 for Raspberry Pi - side 1
Four Serial Ports RS232-RS485 for Raspberry Pi - side 2
Four Serial Ports RS232-RS485 for Raspberry Pi - side 3
Four Serial Ports RS232-RS485 for Raspberry Pi - side 4
Four Serial Ports RS232-RS485 for Raspberry Pi - back view
Four Serial Ports RS232-RS485 for Raspberry Pi - 360 view
SKU: SM-I-026

Four Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi

Four serial ports confugurable as RS232 or RS485 from DIP switches. Non-stackable

In stock
$50.00

Overview

Compatible with all Raspberry Pi models from the Raspberry Pi 4 to Raspberry Pi 5, the Four Serial Ports HAT provides a compact and reliable solution for adding four industrial serial communication ports to your Raspberry Pi. Each port can be independently configured as either RS-232 or RS-485 using onboard DIP switches, providing the flexibility to connect a wide variety of serial devices and industrial equipment.

The card uses the Raspberry Pi's native UART interfaces, requiring no additional software or proprietary drivers—full support is included in the standard Linux kernel. An extra-tall 2×20 GPIO connector allows the card to be stacked on top of virtually any other Raspberry Pi HAT, making it easy to integrate serial communications into existing systems.

  • Four serial ports — each independently configurable as RS-232 or RS-485 via DIP switch
  • RS485 max 921,600 bps · RS232 max 230,400 bps
  • On-board RS485 terminators selectable per port — no jumpers required
  • Uses Raspberry Pi UART1–UART4 (GPIO connector) — no I2C, no custom software
  • Extra-tall 2×20 connector — installs on top of any stackable HAT, or under any HAT
  • Compatible with all Raspberry Pi models from Zero through Raspberry Pi 5
  • No additional software required — drivers included in the Linux kernel

INTERFACES AND I/O

Serial Ports To Raspberry Pi Port Allocation (V2.x)
• PORT 1 — RS232 or RS485 (DIP selectable) • UART1 (GPIO pins 8, 10) • PORT1 → /dev/ttyAMA0
• PORT 2 — RS232 or RS485 (DIP selectable) • UART2 (GPIO pins 21, 24) • PORT2 → /dev/ttyAMA3
• PORT 3 — RS232 or RS485 (DIP selectable) • UART3 (GPIO pins 32, 33) • PORT3 → /dev/ttyAMA4
• PORT 4 — RS232 or RS485 (DIP selectable) • UART4 (GPIO pins 7, 29) • PORT4 → /dev/ttyAMA2
OTHER FEATURES
• Per-port RS485 termination resistor via DIP switch — no jumpers required
• Extra-tall 2×20 connector — stackable under or on top of any HAT
• No software required — Linux kernel drivers · One card per Raspberry Pi
• Compatible with all Raspberry Pi models (Zero through RPi 5); older models support PORT4 only

 

DESCRIPTION

The latest versions of the Raspberry Pi have up to four UART ports on the GPIO connector, but you cannot use them without a physical layer transceiver.

Raspberry Pi Serial Ports

The Four Serial Ports Card is the perfect solution for connecting your Raspberry Pi to serial devices like sensors and industrial equipment. It supports RS485 and RS232 communication protocols, making it versatile for a wide range of applications. Version 2 allows each port to be individually selected as RS485 or RS232, with on-board terminators available for each RS485 port selection.

Data Rates

RS485 Ports: Max 921,600 bps
RS232 Ports: Max 230,400 bps

Enabling the UARTs

To enable all ports on Raspberry Pi 4 & 5, edit /boot/firmware/config.txt and add:
enable_uart=1
dtoverlay=uart5
dtoverlay=uart4
dtoverlay=uart3
dtoverlay=uart2
Save and restart to activate. Verify with ls /dev.

Port Allocation — V1.x

PORT1 → /dev/ttyAMA4
PORT2 → /dev/ttyAMA3
PORT3 → /dev/ttyAMA2
PORT4 → /dev/ttyAMA0

Stacking

Since the card uses the Raspberry Pi UART ports, only one card can be installed per Raspberry Pi. The card is equipped with an extra-tall 2×20 male-female connector and can be installed on top of any stackable HAT. Any Raspberry Pi HAT can also be installed on top of this card.

TECHNICAL DETAILS

CARD LAYOUT

Four Serial Ports for Raspberry Pi Layout

DIP SWITCH CONFIGURATION

The four positions from the left activate the RS485 terminators (one per port). The next four positions select each port as RS232 or RS485.

MECHANICAL SPECIFICATIONS

The card has the same mechanical specifications as all the Sequent Microsystems cards in the Industrial Automation family.

Four Serial Ports for Raspberry Pi mechanical dimensions

COMPATIBILITY

The Four Serial Ports Card is compatible with Raspberry Pi versions 4 and 5. Older versions of the Raspberry Pi do not have all four serial ports available on the GPIO connector and can use only PORT4.

POWER REQUIREMENTS

The card takes 5V and less than 40mA of power from the Raspberry Pi GPIO connector.

DOWNLOADS

User's Guide (PDF) Schematics (PDF) CAD Setup & Documentation
User's Guide V1 Schematic V1 3D STEP Model V1
User's Guide V2 Schematic V2 3D STEP Model V2

WHAT'S INCLUDED

When you purchase the 4-Serial Ports Card you will receive the following items:

1. Four Serial Ports add-on HAT for Raspberry Pi
Four Serial Ports 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

Brass mounting hardware
4. Connector Plugs
Connector Plugs for Four Serial Ports for Raspberry Pi

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