• Mounting holes for use with the AB Electronics UK mounting kits (sold separately)
  • Stackable with other Raspberry Pi accessory boards.
  • Control the Raspberry Pi over RS232 or connect to external serial accessories.
  • RS232 Master Port.

The AB Electronics RS232 Serial Pi Plus HAT is a communication board supporting the RS232 serial protocol.

The RS232 port is connected to the UART port on the Raspberry Pi using a MAX3232 interface. The MAX3232 IC converts the 3.3V UART port to RS232 voltages allowing communication with RS232 compatible devices over a DB9 serial cable or with the use of a null-modem cable the board allows terminal access with Linux on the Raspberry Pi using a terminal application. The RS232 port can be accessed through the DB9 port or the solder points on the PCB.

An array of 2.54mm pitch holes with 3.3V and 5V connections are also provided on the PCB allowing you to build additional circuits on the board.

Please note that you can only use one Serial Pi board on a Raspberry Pi. if stacking with other boards we recommend putting the Serial pi at the top of the stack due to the height of the DB9 connector.

Connecting to the RS232 Port. You need to use the latest Raspbian Jessie release and disable the built-in Bluetooth to use the Serial Pi Plus on the Raspberry Pi 3 or Raspberry Pi Zero W, see our KB page for the config changes needed.

The RS232 port on the Serial Pi can be accessed through the male DB9 socket or the solder points on the PCB. The DB9 socket is configured as a master socket like you will find on desktop computers allowing you to connect external serial devices with a standard RS232 cable.

Input Ratings & Specifications

  • Supply Voltage: 3.3V to 5.5V
  • Logic Voltage at UART Port: 3.3V
  • Maximum Data Rate: 250 bits/s
  • RS232 Input voltage range: -25V to +25V
  • RS232 Output voltage range: -13.2V to +13.2V


The Serial Pi Plus is supplied with the 40 pin GPIO connector and the DB9 connector unsoldered.

Before using the Serial Pi Plus you will need to solder both connectors onto the PCB. We suggest soldering the 40 pin GPIO connector first and then the DB9 connector. 

Form FactorModule
Card TypeModule
Number of Supported Devices1
Data Transfer Rate(s)250 Kbps
Internal Connectors1 x 40 pin GPIO header
External Connectors1 x Serial Port