Home » Two Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi with labeled connectors and status LEDs
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi with green pluggable connectors and GPIO pins.
Two Serial Ports RS485 and RS232 stackable HAT mounted on a Raspberry Pi board showing connectors and GPIO pins.
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi with GPIO connectors and status LEDs.
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi GPIO pins with green pluggable connectors and status LEDs.
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi with labeled connectors and status LEDs
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi with green pluggable connectors and GPIO pins.
Two Serial Ports RS485 and RS232 stackable HAT mounted on a Raspberry Pi board showing connectors and GPIO pins.
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi with GPIO connectors and status LEDs.
Two Serial Ports RS485 and RS232 stackable HAT mounted on Raspberry Pi GPIO pins with green pluggable connectors and status LEDs.
SKU: SM-I-025

Two Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi

One RS485 and one RS232 drivers connected to Raspberry Pi UARTS 1 and 3; Works with Raspberry Pi 3-5;

In stock
$25.00

Overview

Two Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi. The latest Raspberry Pi models expose up to four UART ports on the GPIO header, but none of them work without a physical layer transceiver. This HAT uses two of them to add one RS485 port and one RS232 port, the perfect solution for connecting sensors and industrial equipment, with no additional software required.

  • One RS485 port (UART1, GPIO pins 8, 10) and one RS232 port (UART3, GPIO pins 32, 33)
  • No additional software required — drivers included in the Linux kernel
  • Stackable with any other HAT via an extra-tall 2x20 connector (only one Two Serial Ports card per Raspberry Pi)
  • Compact size — 93mm x 14.2mm, probably the smallest HAT in the world
  • Pluggable connectors, 26-16 AWG wires
  • Status LEDs on both serial ports
  • Compatible with Raspberry Pi versions 2 to 5
  • ECCN Code EAR99 · Ambient operating temperature: -40°C to 85°C

INTERFACES AND I/O

I/O's Communication Software Integration
• One RS485 Port (UART1, GPIO pins 8, 10)
• One RS232 Port (UART3, GPIO pins 32, 33)
Other Features
• No additional software required — drivers included in the Linux kernel
• Stackable with any other HAT (one card per Raspberry Pi) • Pluggable connectors, 26-16 AWG wires
• Status LEDs on both serial ports • ECCN Code EAR99

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 Two 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.

RS485 Port

Connected to Raspberry Pi UART1 (GPIO pins 8, 10) and exposed as /dev/ttyAMA0, supporting speeds up to 921,600 bps. UART1 is available on all Raspberry Pi versions, so this port always works.

RS232 Port

Connected to Raspberry Pi UART3 (GPIO pins 32, 33) and exposed as /dev/ttyAMA4, supporting speeds up to 230,400 bps.

Enabling the UARTs

Edit /boot/firmware/config.txt and add:
enable_uart=1
dtoverlay=uart1
dtoverlay=uart3
Save and reboot to activate. Verify with ls /dev.

Stacking

Since the card uses the Raspberry Pi UART ports, only one Two Serial Ports card can be installed per Raspberry Pi. The card has an extra-tall 2x20 male-female connector, so it can be installed on top of any stackable HAT, and any Raspberry Pi HAT can be installed on top of it.

TECHNICAL DETAILS

CARD LAYOUT

Two Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi board layout

MECHANICAL SPECIFICATIONS

The Two Serial Ports Card is probably the smallest HAT in the world, measuring only 93mm x 14.2mm.

Two Serial Ports RS485 and RS232 Stackable HAT for Raspberry Pi mechanical dimensions

ELECTRICAL SPECIFICATIONS

Power
Power supply 5V from the Raspberry Pi GPIO connector
Power consumption Less than 40 mA @ 5V
RS485 Port
Maximum baud rate 921,600 bps
RS232 Port
Maximum baud rate 230,400 bps

POWER REQUIREMENTS

Power supply: The card takes 5V and less than 40mA of power directly from the Raspberry Pi GPIO connector — no external power supply is required.

PLUGGABLE CONNECTORS

Both serial ports use pluggable screw-terminal connectors accepting 26-16 AWG wires.

COMMUNICATION INTERFACES

RS485 Port

The RS485 transceiver is connected to Raspberry Pi UART1 (GPIO pins 8, 10) and exposed as /dev/ttyAMA0, supporting speeds up to 921,600 bps. UART1 is available on all Raspberry Pi versions, so this port always works — no additional software is required.

RS232 Port

The RS232 transceiver is connected to Raspberry Pi UART3 (GPIO pins 32, 33) and exposed as /dev/ttyAMA4, supporting speeds up to 230,400 bps.

COMPATIBILITY

Interface Direct GPIO UART — no I2C or SPI required
GPIO used GPIO pins 8, 10 (UART1, RS485) and GPIO pins 32, 33 (UART3, RS232)
Max stack One card per Raspberry Pi (uses the Raspberry Pi's own UART ports); other, non-serial HATs can still be stacked above or below it
Compatible with Raspberry Pi versions from 2 to 5. UART1 (pins 8, 10) is available on all Raspberry Pi versions, so the RS485 port always works; UART1 might not be available on older versions or on other boards that emulate the Raspberry Pi GPIO connector.

DOWNLOADS

User's Guide (PDF) Schematics (PDF) CAD Software & Integrations
Schematic V1 3D STEP Model
User's Guide V2 Schematic V2 3D STEP Model (with Raspberry Pi)

WHAT'S INCLUDED

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

1. Two Serial Ports add-on HAT for Raspberry Pi
RS485 and RS232 Ports for Raspberry Pi
2. Mounting Hardware
Brass standoffs for Two Serial Ports HAT for Raspberry Pi
  • Two M2.5x19mm male-female brass standoffs
  • Two M2.5x5mm brass screws
  • Two M2.5 brass nuts
3. Connector Plugs
Pluggable connectors for Two Serial Ports HAT for Raspberry Pi

QUICK START

  1. Plug your card on top of your Raspberry Pi and power up the system. The extra-tall 2x20 connector lets you stack other HATs above or below this card.
  2. Edit /boot/firmware/config.txt (or /boot/config.txt on older Raspbian) and add:
    enable_uart=1
    dtoverlay=uart1
    dtoverlay=uart3
  3. Reboot, then run ls /dev to confirm /dev/ttyAMA0 (RS485) and /dev/ttyAMA4 (RS232) are present.

No additional software is required — all the drivers are part of the Linux kernel. See the Downloads tab for the schematics and user's guide.

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