MMCD Datalogger

Cross-platform diagnostic and datalogging tool for pre-OBDII (1990–1994) Mitsubishi vehicles — Eclipse, Eagle Talon, Plymouth Laser, Galant (4G63).

A modern Go rewrite with both a desktop GUI (Wails v2 + Svelte) and a headless CLI.

⚠️ Pre-release (v0.3.x) — This version has not yet been tested on a live vehicle. It includes a built-in demo simulator and can load recorded logs (including classic PalmOS MMCd .pdb files) for full UI and workflow testing. Once validated on-vehicle, it will be promoted to v1.0.0.

Features

Desktop GUI

• Three data source modes — Live ECU, Demo Simulator, or Load Log File
• Real-time dashboard — Live sensor tiles for all 22 channels
• Scrollable graph — 30,000-sample deep history buffer with viewport scrolling
• Sample-pinned crosshair — Click to pin, arrow keys to step sample-by-sample, Escape to unpin
• Elapsed time display — Time shown on X axis and in crosshair readout panel
• Draggable scrollbar — Click, drag, or mouse wheel (vertical + horizontal) to navigate
• Shared history — Switch between Dashboard and Graph without losing data
• Log file viewer — Load and review CSV, .mmcd, or PalmOS PDB files directly in the graph
• DTC read/erase — Read active and stored diagnostic trouble codes
• Actuator tests — Fuel pump, purge solenoid, EGR, injector disable
• CSV recording — Record live data to timestamped CSV while monitoring
• Demo mode — Built-in ECU simulator with realistic driving scenarios (idle → accel → cruise → decel) for UI testing without hardware

Headless CLI

• Datalogging — Log sensors to CSV with live terminal display
• DTC diagnostics — Read/erase trouble codes from the command line
• Actuator testing — Trigger solenoid tests over serial
• Log import — Convert PalmOS PDB files to CSV or native binary format
• Log review — Display saved logs in the terminal
• Cross-platform — Runs on Raspberry Pi, SSH sessions, or anywhere without a display

Screenshots

Dashboard — Live Sensor Tiles

Graph — Scrollable History with Crosshair

Download

Pre-built binaries are available on the Releases page — no development tools required.

You don't need a vehicle or hardware to explore the app — use Demo mode for a simulated ECU, or load a recording (CSV, .mmcd, or PalmOS .pdb) to review real data.

Quick Start (Developers)

Prerequisites

• Go 1.22+
• Node.js 18+ (for frontend build)
• Wails CLI v2 (for desktop GUI — installed automatically by make setup)

Linux System Libraries

Wails requires GTK3 and WebKit2GTK on Linux. Install them for your distro:

# Ubuntu 24.04+ / Debian 13+
sudo apt install libgtk-3-dev libwebkit2gtk-4.1-dev

# Ubuntu 22.04 / Debian 12
sudo apt install libgtk-3-dev libwebkit2gtk-4.0-dev

# Fedora
sudo dnf install gtk3-devel webkit2gtk4.1-devel

# Arch
sudo pacman -S gtk3 webkit2gtk

macOS

No extra system libraries needed — Wails uses the native WebView.

Setup (New Machine)

# Clone the repo
git clone https://github.com/kevin-buckham/MMCd-Go.git
cd MMCd-Go

# One command: checks Go, Node, Linux libs, installs Wails CLI, npm install, go mod tidy
make setup

make setup will:

1. Verify Go and Node.js are installed
2. Check for required Linux system libraries (on Linux)
3. Install the Wails CLI if it's not already present
4. Run npm install and go mod tidy

You can also run make check at any time to verify all prerequisites without installing anything.

Build the Desktop App

# Build the app (produces build/bin/mmcd on Linux, build/bin/mmcd.app on macOS)
make build

Run the Desktop App

# macOS
open build/bin/mmcd.app

# Linux / Windows
./build/bin/mmcd

On launch you'll see the data source selector in the header:

• Live ECU — Select your serial port and connect to a real ECU
• Demo — Start the built-in simulator (no hardware needed)
• Load File — Open a CSV, .mmcd, or PDB log file for review

Build CLI Only (no Wails/frontend needed)

make cli
# Binary at bin/mmcd

Development Mode (hot reload)

make dev

This runs wails dev which starts the Go backend and Svelte frontend with hot reload — changes to .svelte files update instantly in the app window.

Run Tests

make test

Hardware

You need a USB-to-TTL serial adapter (FTDI FT232, CH340, CP2102, etc.) and a 1N4148 diode (or Schottky equivalent). No MAX232 level shifter is needed — the FTDI connects directly to the ECU's ALDL connector at TTL levels.

ALDL Connector Pinout

  ┌─────────────────────────────┐
  │  1  2  3  4  5  6  7  8    │  ALDL 12-pin connector
  │  9  10 11 12               │  (under dash, driver side)
  └─────────────────────────────┘
   │      │      │
   │      │      └── Pin 12: Ground
   │      └── Pin 10: Diagnostic enable (short to ground)
   └── Pin 1: Serial data (bidirectional)

Cable Schematic

This "universal" cable design works with MMCd, TunerPro, and EvoScan. The data line (Pin 1) is bidirectional — the ECU transmits and receives on the same wire. A diode on the TX line prevents the adapter's transmit signal from fighting the ECU's responses.

FTDI/USB-TTL Adapter                           ALDL Connector
─────────────────                              ──────────────

RX  (Yellow/White) ─────────────────────────── Car Pin 1 (Data)

                        1N4148 Diode
TX  (Green) ────────────┤►├────────────────── Car Pin 1 (Data)
                   (cathode→FTDI)
                   (anode→car)

GND (Black) ────────────────────────────────── Car Pin 12 (Ground)

                    Car Pin 10 ──── Car Pin 12 (jumper to enable diag mode)

Diode Details

The diode on TX ensures the adapter only drives the line low and doesn't hold it high between bytes, which would block the ECU's open-collector responses.

• 1N4148 (silicon): Forward drop ~0.7V. Works for 99% of setups.
• BAT85 or 1N5817 (Schottky): Forward drop ~0.2–0.3V. Cleaner logic low with extra margin. Use this if you have one.

Orientation: Stripe (cathode) → towards FTDI adapter. Non-stripe (anode) → towards car.

Serial settings: 1953 baud, 8 data bits, 1 stop bit, no parity, no flow control.

CLI Usage

# List available sensors
mmcd sensors

# Show version and about info
mmcd about
mmcd --version

# Start datalogging with live terminal display
mmcd log -p /dev/ttyUSB0 --sensors RPM,TPS,COOL,TIMA --output log.csv --display

# Log all sensors
mmcd log -p /dev/ttyUSB0 --sensors all --output log.csv

# Read diagnostic trouble codes
mmcd dtc -p /dev/ttyUSB0

# Read and erase DTCs
mmcd dtc -p /dev/ttyUSB0 --erase

# Run actuator test
mmcd test -p /dev/ttyUSB0 --command fuel-pump

# Review a saved log
mmcd review --file log.csv

# Import PalmOS PDB log to CSV
mmcd import --file 2003-01-17_First_run.PDB

# Import to native binary format
mmcd import --file 2003-02-01_YEMELYA.PDB --format mmcd

# Import with imperial units
mmcd import --file log.PDB --units imperial

Common Flags

Supported Sensors

Log Formats

CSV (default)

Human-readable timestamped log with both converted values and raw bytes. Each sensor gets two columns: SLUG (formatted value) and SLUG_raw (0–255). Created by mmcd log or mmcd import --format csv.

.mmcd (native binary)

Compact binary format for efficient storage and replay. 48 bytes per sample (8-byte nanosecond timestamp + 4-byte dataPresent bitmask + 32-byte raw data + 4 bytes padding). Created by mmcd import --format mmcd. Can be loaded in the desktop GUI for graph review.

PDB (PalmOS import)

The original MMCd PalmOS app stored logs as .PDB database files using the FileStream DBLK format. These contain 40-byte GraphSample structs (big-endian) with PalmOS epoch timestamps. Use mmcd import --file log.PDB to convert, or load directly in the desktop GUI.

Project Structure

mmcd-go/
├── main.go                     # Entry point: CLI dispatch or Wails GUI launch
├── app.go                      # Wails bindings (frontend ↔ Go backend)
├── internal/
│   ├── version/version.go      # App version, license, attribution constants
│   ├── sensor/
│   │   ├── definitions.go      # 22 sensor definitions with addresses and conversions
│   │   ├── convert.go          # Byte → engineering unit conversion functions
│   │   └── sample.go           # Sample struct (raw data + timestamp + bitmask)
│   ├── protocol/
│   │   ├── serial.go           # Serial port wrapper (1953 baud, 8N1)
│   │   ├── ecu.go              # ECU request-reply protocol (PollSensors)
│   │   ├── dtc.go              # DTC decoding and erase commands
│   │   └── simulator.go        # Fake ECU for demo mode (realistic driving cycles)
│   ├── logger/
│   │   ├── logger.go           # Polling loop with SamplePoller interface
│   │   ├── csv.go              # CSV writer (timestamped, dual-column)
│   │   ├── csv_reader.go       # CSV reader for log file loading
│   │   ├── store.go            # Native binary .mmcd format (read/write)
│   │   └── pdb.go              # PalmOS PDB parser (DBLK/GraphSample)
│   └── cli/
│       ├── root.go             # Cobra root command + about subcommand
│       ├── log.go              # `mmcd log` — live datalogging
│       ├── dtc.go              # `mmcd dtc` — read/erase DTCs
│       ├── test.go             # `mmcd test` — actuator tests
│       ├── review.go           # `mmcd review` — display saved logs
│       ├── import.go           # `mmcd import` — PDB/format conversion
│       └── sensors.go          # `mmcd sensors` — list sensor definitions
├── frontend/
│   └── src/
│       ├── App.svelte          # Main app shell, data source selector, shared history
│       ├── app.css             # Dark theme styles
│       └── lib/
│           ├── Dashboard.svelte # Live sensor tile grid
│           ├── Graph.svelte     # Scrollable graph with crosshair + scrollbar
│           ├── DTCPanel.svelte  # DTC read/erase UI
│           ├── TestPanel.svelte # Actuator test UI
│           ├── Settings.svelte  # Unit system + sensor configuration
│           └── About.svelte     # Version, license, attribution
├── Makefile                    # Build targets: build, dev, cli, test, clean
├── LICENSE                     # GPL-2.0-or-later
└── README.md

Protocol

The MMCD protocol is a simple request-reply over serial:

1. Send 1 byte (sensor address)
2. Receive 2 bytes (echo of address + data byte)
3. Apply conversion formula to get engineering units

The ECU uses an open-collector data line — both TX and RX share a single wire (ALDL Pin 1). The diode on the cable's TX prevents bus contention.

Serial settings: 1953 baud, 8 data bits, 1 stop bit, no parity, no flow control.

License

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License v2 or later as published by the Free Software Foundation. See LICENSE for the full text.

Inspired by and thanks to the original MMCd PalmOS datalogger by Dmitry Yurtaev (GNU GPL v2).

Developers: Kevin Buckham & Claude (Anthropic)

© 2026 Kevin Buckham & Claude (Anthropic)