- RS232 Master Port.
- Control the Raspberry Pi Zero 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 Zero is a communication board supporting the RS232 serial protocol, designed for use on the Raspberry Pi and other compatible single-board computers.
RS232 is widely used for connecting computers to devices such as modems, printers, data terminals and various industrial equipment. Despite being an older technology, it remains prevalent in various legacy systems and industrial applications.
The RS232 port is connected to the GPIO UART port on the Raspberry Pi using a MAX3232 or ICL3232ECBNZ* RS232 transceiver. The RS232 transceiver chip converts the 3.3V UART port to RS232 voltages, allowing communication with RS232 compatible devices over a DB9 serial cable.
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 Zero board on a Raspberry Pi. If stacking with other boards, we recommend putting the Serial Pi Zero at the top of the stack due to the height of the DB9 connector.
*Due to global component shortages, Serial Pi Plus boards manufactured after 23/11/2022 may use the Intersil ICL3232ECBNZ RS232 interface IC. The ICL3232ECBNZ is a pin-compatible replacement for the Texas Instruments MAX3232.
Technical Details
Input Ratings & Specifications
- Spec
- Ratings
- Supply Voltage
- 3.3V to 5.5V
- Logic Voltage at UART Port
- 3.3V
- 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
Serial Pi Zero - 3D CAD File (STEP Format)
Schematic
View the schematic PDF.
Mechanical Drawings
Compatibility
We have tested the Serial Pi Zero on the following platforms.
| Model |
Status |
| Raspberry Pi Model A / B |
|
| Raspberry Pi 1 Model A+ / B+ |
|
| Raspberry Pi 2 Model B |
|
| Raspberry Pi 3 Model A+ / B / B+ |
|
| Raspberry Pi 4 Model B |
|
| Raspberry Pi 5 |
|
| Raspberry Pi Zero |
|
| Raspberry Pi Zero W / Zero 2 W |
|
| Raspberry Pi Compute Module 4 IO Board |
|
| Raspberry Pi 400 |
|
| Orange Pi |
|
| Odroid |
|
*You need to use the latest Raspberry Pi OS release and disable the built-in Bluetooth to use the Serial Pi Zero on the Raspberry Pi 3, 3+ and 4. See our Serial Port Tutorial for the config changes needed.
Assembly Instructions
The Serial Pi Zero is supplied with the 40-pin GPIO connector, and the DB9 male connector unsoldered.
Before using the Serial Pi Zero, you 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 for the Serial Pi Plus, which uses the same assembly steps as the Serial Pi Zero.
Watch our assembly guide on YouTube. (opens in a new window)
PCB Header Assembly Jig
Download and print our PCB Header Assembly Jig to hold your circuit board when soldering the header pins.
RS232 Port
RS232 port pin-out connections
| 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 needing an ethernet connection. You must use a Null-Modem cable to connect the Serial Pi to a desktop computer. 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 connections
| Connector 1 |
Connector 2 |
Function |
| 2 |
3 |
Rx ← Tx |
| 3 |
2 |
Tx → Rx |
| 5 |
5 |
Ground |
