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

• Adafruit PyRuler Learning Guide
• Trinket M0 CircuitPython Guide