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The Adafruit PyRuler is a PCB reference ruler and a fully functional CircuitPython microcontroller in one. Measuring approximately 25 × 150 mm (1" × 6"), thi...

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The Adafruit PyRuler is a PCB reference ruler and a fully functional CircuitPython microcontroller in one. Measuring approximately 25 × 150 mm (1" × 6"), this gold-plated FR4 ruler features common SMD component package outlines, a font size guide, trace-width diagram, and AWG wire gauge drill holes — all the references an electronics engineer needs at a glance.

Built into the end of the ruler is a Trinket M0 (ATSAMD21 Cortex-M0+) with four capacitive touch pads and matching LEDs. Out of the box, it ships with CircuitPython and can act as a USB keyboard — touch the pads to type special characters like Ω, µ, and π. Edit the on-board code.py file in any text editor to customise the behaviour.

Key Features

  • PCB Reference Ruler – Gold-plated with SMD package outlines, font sizes, trace widths, and AWG drill holes
  • ATSAMD21E18 Processor – 48 MHz Cortex-M0+ with 256 KB flash and 32 KB RAM
  • 4 Capacitive Touch Pads – Each with a matching coloured LED (red, yellow, green, blue)
  • USB Keyboard Mode – Type Ω, µ, π, and custom characters by touching the pads
  • CircuitPython Pre-Loaded – Shows up as a USB drive; edit Python code in any text editor
  • Arduino Compatible – Can also be programmed with the Arduino IDE
  • Native USB – Serial console, HID keyboard/mouse, and small disk drive
  • RGB DotStar LED – Plus green power LED and red pin 13 LED
  • 5 GPIO Header Pins – 3 ADC, 1 DAC, 2 PWM, 3 extra capacitive touch; not shared with USB or touch pads
  • Hardware SPI, I2C & Serial – True hardware support on dedicated pads
  • NeoPixel & DotStar Support – Drive 8,000+ pixels with DMA on one pin
  • USB or Battery Power – Automatic switchover between USB and external power

Ideal For

  • Electronics engineers needing a quick SMD package reference
  • CircuitPython beginners looking for an easy first project
  • Custom USB keyboard shortcuts and special character input
  • Desk accessories and engineering gifts

Resources

Jargon buster

Plain-language definitions for the technical terms used above.

ADC
An analogue-to-digital converter reads a changing voltage and turns it into a number the microcontroller can use. It matters when connecting analogue sensors such as light, sound, or variable-resistor sensors.
AWG
American Wire Gauge is a numbering system for wire thickness, where a lower number means a thicker wire. The AWG rating matters because thicker wire can usually carry more current with less voltage drop and heating.
CircuitPython
A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.
DAC
A digital-to-analogue converter turns numbers from the microcontroller into a real analogue voltage. It matters if you want to generate simple waveforms, audio-style signals, or variable control voltages rather than just on/off outputs.
GPIO
General-purpose input/output pins are microcontroller pins you can set in software to read signals, switch devices on and off, or connect to peripherals. The number of GPIO pins matters because it limits how many buttons, LEDs, sensors, and other parts you can wire directly to the board.
HID
Human Interface Device is a USB device class used for keyboards, mice, gamepads and similar controls. If a board supports HID over USB, it can act like an input device to a computer without needing a custom driver.
I2C
I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
IDE
Short for Integrated Development Environment, a program used to write, run and manage code. It matters because some learners prefer a traditional coding workspace instead of a guided notebook-style lesson.
LED
A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
microcontroller
A microcontroller is a small computer on a chip that runs your program and controls connected inputs and outputs. For this product, it is the part that reads buttons and sensors, drives the display and speaker, and communicates over Bluetooth.
native USB
Native USB means the microcontroller itself handles USB communication, rather than using a separate USB-to-serial chip. This matters for programming, debugging, and projects that need the board to act directly as a USB device.
NeoPixel
A type of addressable LED system where colour data is sent along a single digital data line from one LED or controller to the next. Compatibility matters because the timing and signal format must match for the lights or driver board to respond correctly.
PCB
A printed circuit board is a rigid board with copper tracks that connect electronic parts without loose wires. For this kit, the PCBs also form the airplane shape, so they are both the circuit base and part of the finished model.
PWM
Pulse Width Modulation is a way for a digital pin to simulate variable output power by switching on and off very quickly. It matters for controlling things like LED brightness, motor speed, or servo-style signals from a microcontroller pin.
RAM
RAM is temporary memory used while a device is running, and its contents are lost when power is removed. A “Run in RAM” mode is useful for testing settings without permanently programming the module, but it may not support every feature.
RGB
Short for red, green and blue, usually referring to an LED that can mix those three colours. It matters because controlling an RGB LED teaches how separate outputs combine to create different colours.
SPI
A fast serial communication bus often used for displays, memory cards, and sensors. It matters because SPI devices need specific pins for clock and data, plus a separate chip-select line for each device.

Related Tutorials

Free guides on learn.littlebird.com.au

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