Overview

A single-dose coffee grinder built around a Raspberry Pi, a configurable stepper-motor drive, and a 1.28-inch round touchscreen. The whole interface is one circular dial: drag around the ring to set the speed, tap the center to start or stop. Custom-modeled, 3D-printed parts make up the body and hopper.

Key features

• Circular touchscreen UI rendered at 2x for crisp anti-aliased graphics, with whole-bean and ground-coffee icons for the start/stop state
• Speed dial from 0 to 300, displayed at the real burr RPM after the gearbox reduction
• Configurable motor profiles (drive current, PWM frequency, microstepping, decay mode) selectable from a JSON config library
• Automatic display standby after ten minutes of inactivity to protect the panel
• Headless deployment: systemd services for the motor controller and first-boot WiFi setup, installed by a single script

Technical details

Motor control

• Stepper drive over Raspberry Pi GPIO with tuned current, blanking, decay, and microstep parameters per profile
• The grind run is spawned as a separate process so the UI thread stays responsive while the motor is under load

Interface

• Touch input is mapped from screen coordinates to either the dial angle (speed) or the center button (start/stop), with separate hit radii so the two never conflict
• Diagnostic and motor-only test utilities for bring-up and tuning

Hardware

The body, hopper, and mounting are modeled as printable parts (shown above). Drag to rotate, scroll to zoom; each is a binary STL.