• 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.

Introduction:

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.

Compatibility Chart

Model	Status
Raspberry Pi Model A	No
Raspberry Pi Model B	No
Raspberry Pi 1 Model A+	Yes
Raspberry Pi 1 Model B+	Yes
Raspberry Pi 2 Model B	Yes
Raspberry Pi 3 Model B *	Yes
Raspberry Pi Zero	Yes
Raspberry Pi Zero W	Yes
Orange Pi	Yes
Asus Tinker Board	Yes

*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, see our KB page for the config changes needed.

Connecting to the RS232 Port

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.

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

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

Schematic

Click to download schematic PDF.

Assembly Instructions

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 jigwhich 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.

Mechanical Drawings

Click image to enlarge

Sample Code & Tutorials

Configuring the RS232 communication on the Raspberry Pi

Legacy Serial Pi Versions

See our KB article for previous versions of this board.