Serial Wombatâ„¢ I/O Expansion chips

Smart I/O Expansion for Arduino, Raspberry Pi, CircuitPython, native embedded systems, PC, or any other system that can communicate by UART or I2C.

Serial Wombat chips extend your system’s I/O capabilities and promote cross-platform compatibility.

A Serial Wombat chip is an ideal accessory when you need a few more I/O or need to do tasks that require specialized pin capabilities that aren’t available.

A Serial Wombat chip isn’t a device you program – It’s a helpful accessory that you command to expand your capability. Like other IC’s, it’s easily added to an I2C or Serial Bus. Unlike other IC’s, it has built in firmware that lets you offload simple but timing sensitive tasks from your code or sketch to the Serial Wombat chip’s firmware and CPU.


The Serial Wombat family of chips has an Arduino library available through the Arduino Library manager which makes interfacing to it very easy on the Arduino Platform.

Check out the Arduino Library API here.


C# .Net Core libraries and Python Libraries for Raspberry Pi will be available soon.

You can also command the Serial Wombat directly using its simple 8 byte per packet protocol over I2C or UART.


The Serial Wombat family of chips has many YouTube video tutorials to help you get started.

Check out the Serial Wombat YouTube Channel here


The Serial Wombat firmware is an Open Source Project (MIT License).

Source code and technical documentation are available at https://github.com/BroadwellConsultingInc/SerialWombat

The Serial Wombat project was developed to showcase the embedded systems development capabilities of Broadwell Consulting Inc. Need help with a commercial embedded project? Contact us.

Serial Wombat is a trademark of Broadwell Consulting Inc. See here for more information.


Available Models

Serial Wombat 4A I/O expansion chip – For UART

Available Soon…

The Serial Wombat 4A I/O expansion chip provides 4 Input/Output pins each capable of running an independent state machine every millisecond to perform smart operations. Communications use a simple 8 byte protocol at 115,200 bps.

Each pin can be configured for any of the following in any combination:

  • Digital Input with optional Pull-Up
  • Pulse Measurement – Pulse Measurement with a resolution as high as 8uS, useful for measuring frequency, duty cycle, or Pulse High Time (e.g. RC servo receiver output)
  • Debounced Input – Debounces switches, as well as keeping track of press count and time button has been depressed
  • Quadrature Decoder – Combine two input pins to monitor quadrature encoder signals and measure up to 10,000 directional ticks per second.
  • Digital Output (standard or open-drain), up to 25mA Sink/Source
  • Analog Input (10-bit with filtering, averaging and Min/Max tracking)
  • Servo Output ( 1uS pulse resolution)
  • PWM Output (8 or 10 bit resolution at select frequencies ranging from 1Hz to 38kHz)
  • Watchdog Function – Can pull the host’s reset pin if not reset after a configurable time period
  • Protected Output – A digital output that monitors another pin’s digital or analog value and changes to a safe state if a fault exists for a configurable amount of time

Serial Wombat 4B I/O Expansion Chip – For I2C

Preprogrammed ICs and support components are available now on Amazon in a 4-pack with 4 different I2C addresses:

Click here to purchase on Amazon.

The Serial Wombat 4B I/O expansion chip provides 3 Input/Output pins and one Input-Only pin each capable of running an independent state machine every millisecond to perform smart operations. Communications use a simple I2C protocol at up to 400kbps. Preprogrammed Serial Wombat 4B chips come in I2C follower addresses 0x6C, 0x6D, 0x6E and 0x6F. You can also download the firmware from Git Hub and recompile with your own address.

Each Pin can be configured for any of the following in any combination:

  • Pulse Measurement – Pulse Measurement with a resolution as high as 8uS, useful for measuring frequency, duty cycle, or Pulse High Time (e.g. RC servo receiver output)
  • Debounced Input – Debounces switches, as well as keeping track of press count and time button has been depressed
  • Quadrature Decoder – Combine two input pins to monitor quadrature encoder signals and measure up to 10,000 directional ticks per second.

Each output pin can be configured for any of the following in any combination:

  • Digital Output (standard or open-drain), up to 25mA Sink/Source
  • Analog Input (10-bit with filtering, averaging and Min/Max tracking)
  • Servo Output ( 1uS pulse resolution)
  • PWM Output (8 or 10 bit resolution at select frequencies ranging from 1Hz to 38kHz)
  • Watchdog Function – Can pull the host’s reset pin if not reset after a configurable time period
  • Protected Output – A digital output that monitors another pin’s digital or analog value and changes to a safe state if a fault exists for a configurable amount of time

One output pin and one input pin can also be configured for UART TX/RX in order for the Serial Wombat 4B chip to act as an I2C <-> UART bridge at as standard baud rates. Bandwidth is reduced vs. a native bus due to the overhead to retransmit data across each bus.