Serial Pi Plus

£8.99 each (including VAT: £10.79)
Product Code:SerialPiPlus
113 in stock to order today.
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  • RS232 Master Port.
  • Control the Raspberry Pi over RS232 or connect to external serial accessories.
  • Stackable with other Raspberry Pi accessory boards.
  • Mounting holes for use with the AB Electronics UK mounting kits (sold separately)

The Serial Pi Plus  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.

Legacy Serial Pi Versions

See our KB article for previous versions of this board.


We have tested the Serial Pi Plus on the following platforms.

Model Status
Raspberry Pi Model A / B No
Raspberry Pi 1 Model A+ / B+ Yes
Raspberry Pi 2 Model B Yes
Raspberry Pi 3 Model A+ / B / B+ Yes
Raspberry Pi 4 Model B Yes
Raspberry Pi Zero Yes
Raspberry Pi Zero W / Zero 2 W Yes
Raspberry Pi Compute Module 4 IO Board Yes
Orange Pi Yes
Asus Tinker Board Yes
Odroid Yes

*You need to use the latest Raspberry Pi OS release and disable the built in Bluetooth to use the Serial Pi Plus on the Raspberry Pi 3, 3+ and 4, see our KB page for the config changes needed.


Ti MAX3232E

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Serial Pi Plus
£8.99 each (including VAT: £10.79)


Input Ratings & Specifications

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

3D CAD Model

Click to downloadSerial Pi Plus - 3D CAD File (STEP Format)


Click to download
Click to download schematic PDF.

Mechanical Drawings

Mechanical Drawing

Click image to enlarge

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Serial Pi Plus
£8.99 each (including VAT: £10.79)


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. 

To make assembly easier we have designed a PCB header assembly jig which you can download and print.

Watch the assembly video, best viewed in 1080p high quality mode:


PCB Header Assembly Jig

Download and print our PCB Header Assembly Jig to hold your circuit board when soldering the header pins.


RS232 Port

The pin-out connections for the RS232 port are shown below:

Pin Usage
1 N/C
2 RX (data receive)
3 TX (data transmit)
4 N/C
5 Ground
6 N/C
7 N/C
8 N/C
9 N/C

DB9 connector as viewed from the front of the Serial Pi Plus

Using the RS232 port for terminal connections

The RS232 port can be used for remote terminal connections on the Raspberry Pi allowing remote access and control without the need for an ethernet connection. In order to connect the Serial Pi to a desktop computer you will need to use a Null-Modem cable. A wiring diagram for making a Null-Modem cable can be found below. For details on configuring the RS232 communication on the Raspberry Pi visit our knowledge base.

Null-Modem Cable

Null modem wiring diagram

Connector 1 Connector 2 Function
2 3 Rx ← Tx
3 2 Tx → Rx
5 5 Ground

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Important Information

This development board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY and is not considered by to be a finished end-product fit for general consumer use. As such, the goods being provided are not intended to be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety and environmental measures typically found in end products that incorporate such semiconductor components or circuit boards. Persons handling the product(s) must have electronics training and observe good engineering practice standards. This development board/kit does not fall within the scope of the European Union directives regarding electromagnetic compatibility, restricted substances (RoHS), recycling (WEEE), FCC, CE or UL, and therefore may not meet the technical requirements of these directives or other related directives. Note: documents in Portable Document Format (PDF) require Adobe Acrobat Reader 5.0 or higher to view, download Adobe Acrobat Reader or other PDF reading software for your computer or mobile device.