P4PP

Precision 4-Point Probe Controller

Windows GUI for operating a 4-point probe system and logging sheet resistance measurements.

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Overview

P4PP is the control application for a custom 4-point probe measurement setup.

It provides:

• motion and hardware control through serial communication
• measurement execution (single or multi-cycle)
• live result visualization
• automatic CSV reporting

Target metric: Sheet Resistance (Rs, Ohm/sq).

Quick Start (1 Minute)

1. Download latest release: https://github.com/changhwang/P4PP/releases/latest
2. In release assets, download P4PP.zip.
3. Extract to a stable folder (example: C:\Tools\P4PP).
4. Open extracted P4PP folder and run P4PP.exe.
5. In the app, keep the default R_set = 681 ohm, then select MOCK and validate Connect -> Home -> Measure.

Important:

• Keep the extracted P4PP folder structure as-is.
• Do not move P4PP.exe outside the P4PP folder.

App Screenshot

Highlights

• Live GUI for connect/home/move/measure workflow
• MOCK mode for validation without hardware
• Real-time status + graph updates
• Auto-save per-measurement CSV reports
• History CSV export
• Explicit controller state handling

Hardware Bring-Up (Real Device)

Before using real hardware:

1. Flash firmware: firmware/p4pp_firmware/p4pp_firmware.ino
2. Confirm COM port in Windows Device Manager.
3. Complete wiring and calibration checks in docs below.

R_set guidance:

• Default startup mode is 681 ohm (~0.1 mA), which is the safer general-purpose option for initial bring-up.
• Switch to 68.1 ohm (~1 mA) for lower-resistance samples such as ITO when you need stronger signal.

Read docs in this order:

1. 4PP Master Guide
2. Analog Wiring Guide
3. Movement Implementation Guide
4. App Architecture

First Real Measurement Checklist

1. Pass full MOCK workflow first.
2. Switch to real COM port and connect.
3. Run one low-risk test sample.
4. Confirm graph updates and CSV output in data/.

Troubleshooting

Serial connection fails

• Recheck COM port in Device Manager.
• Ensure no other application is holding the port.
• Re-test with MOCK mode first.

App does not start (ModuleNotFoundError: tkinter)

• Use the official release package (P4PP.zip) from Releases.
• If you built locally, use Python 3.11 and rebuild with P4PP.spec.

Measured result stays near 0.00

• Confirm the Arduino firmware is updated together with the PC app.
• 681 ohm mode is intended for higher-resistance samples; low-resistance films may require 68.1 ohm.

Build/runtime metadata error (PackageNotFoundError: p4pp)

• Build with main.py as entry script.
• Use the provided P4PP.spec.

Build instability on mixed Python environments

• Build using a clean Python 3.11 virtual environment.
• Clear PYTHONPATH before packaging to avoid external site-package contamination.

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Developer Notes

Repository Structure

P4PP/
|- assets/               # logo/icons
|- data/                 # measurement outputs
|- docs/                 # English docs
|- firmware/             # Arduino firmware
|- src/p4pp/             # application source
|- main.py               # app entry point
|- P4PP.spec             # PyInstaller spec
`- setup.py              # package metadata

Local Run

py -3.11 -m venv venv
.\venv\Scripts\Activate.ps1
python -m pip install --upgrade pip
pip install -e .
python main.py

Build

py -3.11 -m venv build_venv
.\build_venv\Scripts\Activate.ps1
python -m pip install --upgrade pip
python -m pip install pyserial customtkinter matplotlib Pillow pyinstaller
$env:PYTHONPATH = ""
python -m PyInstaller --noconfirm --clean P4PP.spec

Output:

• dist/P4PP/P4PP.exe
• optional archive: dist/P4PP.zip

Distribution Policy

• dist/ is not tracked in main (ignored by .gitignore).
• Binaries are distributed via GitHub Releases assets.
• build/ is temporary and can be deleted safely.

License

Internal R&D project unless otherwise specified. Validate safety and calibration before production usage.