Insole

EPD 3D G6 — Orthomate

Battery-powered adaptive orthopedic insole controller. Redistributes plantar pressure in real-time using three micro linear stepper actuators driven by force sensor feedback. Includes a BLE companion Android app for live monitoring.

🏆 Winner — Top Course Project, EPD 3D Exhibition April 2026

Hardware at a glance

PCB placement

Orthomate uses two custom PCBs that work together inside a modified shoe:

Controller PCB — mounts in a controller module. Houses the ESP32-C6, three TMC2209 stepper drivers, TP4056 charger, XL6009 boost converter, and the 20-pin connector (J9) to the insole. The LiPo battery sits alongside it.

Insole PCB — sits directly underfoot inside the shoe. Hosts the three FSR pressure-sensing zones (metatarsal, arch, calcaneus) and the three micro linear stepper actuator assemblies. The actuators extend upward to redistribute localised plantar pressure. Connects back to the controller PCB via a 20-pin ribbon/wire harness.

Exhibition highlights

Final product

ANSYS stress analysis

Exhibition day

Poster

Downloadable resources

• Orthomate Final Slides (PDF)
• Orthomate Poster (PDF)

Repository structure

orthomate/
├── Electronics Reference.txt           # Hardware design spec (v6.0)
├── BOM.txt                             # Bill of materials
├── firmware/
│   ├── main/                           # Full operational firmware (PlatformIO)
│   │   ├── platformio.ini
│   │   └── src/main.cpp
│   ├── ARDUINO IDE MAIN/               # Arduino IDE version of the full firmware
│   │   └── EPD3DG6_Main/EPD3DG6_Main.ino
│   ├── ARDUINO IDE APP TEST/           # Minimal Arduino IDE sketch for BLE app testing
│   │   └── sketch_apr14a/sketch_apr14a.ino
│   ├── stepper_test/                   # Single-axis stepper back-and-forth smoke test
│   ├── homing_test/                    # Blind homing: retract to min, extend to 12 mm
│   ├── button_test/                    # Button + OLED input test
│   └── oled_test/                      # OLED display test
├── android_app/                        # Kotlin/Compose BLE companion app
│   └── app/src/main/AndroidManifest.xml
├── Controller PCB KiCad Files/         # KiCad schematic + layout for controller PCB
├── Controller PCB Iterations/          # Gerber files from each revision (V2–V5)
├── Insole PCB KiCad Files/             # KiCad schematic + layout for insole PCB
├── Insole PCB Iterations/              # Gerber files from each revision
├── Exhibition Files and Photos/        # Exhibition media, poster, and slides
└── docs/
    ├── FIRMWARE_MAIN.md                # Detailed firmware walkthrough

Firmware — operational logic

The main firmware (firmware/main/) implements a full fitting cycle driven by one button:

DISCONNECTED ──[plug in]──► CONNECTED ──[btn]──► MEASURING
                                                      │ (auto)
                                                  MEASURED ──[btn]──► ACTUATING
                                                                           │ (auto)
                                                                         DONE ──[unplug]──► DISCONNECTED
                                                                         (insole retains shape)

On next plug-in with actuators extended:  DISCONNECTED ──► HOMING ──► CONNECTED

Extension formula: $ext_i \propto (1 - r_i)$ where $r_i = F_i / \sum F$

BLE — Android companion app

The ESP32 advertises a GATT service and notifies a JSON payload at ~4 Hz:

{"fsr1": 42, "fsr2": 18, "fsr3": 75, "mode": "MEASURING", "batt": 67}

The Android app (android_app/) displays real-time FSR forces as animated colour circles, current mode, battery %, and BLE status. See docs/ANDROID_APP_GUIDE.md for build and install instructions.

GPIO assignment (ESP32-C6 SuperMini, Hardware Ref v6.0)

Quick start

• Flash firmware: docs/FLASH_GUIDE.md
• Install Android app: docs/ANDROID_APP_GUIDE.md
• Firmware internals: docs/FIRMWARE_MAIN.md

Design rules

• Charging and actuator operation are mutually exclusive — never simultaneous.
• Never start all 3 motors simultaneously — stagger motor starts by 75 ms.
• Sample FSRs only when motors are idle; use 7-sample median filtering with 4 ms settling per sample.
• ADC attenuation must be set to 11 dB (ADC_11db) on all analog pins for correct readings at the operating voltage range.
• VBAT < 3.35 V → disable actuators; VBAT < 3.5 V → show low battery warning.
• OLED updates are content-cached — only redraws when text changes (prevents I2C writes during motor current spikes).

License

MIT — see LICENSE