Connecting to Your ECU
Live serial connection
VETuner can communicate directly with your ECU over a serial port using the browser's built-in Web Serial API. Currently this is supported by Chome based browsers (Chrome, Chromium, Edge) and Vivaldi. Firefox and Safari do not support this API and cannot be used.
- Plug your ECU into your computer via USB (or a USB-to-serial adapter)
- Open the Connection Setup panel from the sidebar
- Click Connect — your browser will show a port selection dialogue
- Select the correct port and click Connect
Once connected, VETuner will:
- Read the ECU signature and load the matching definition
- Begin streaming real-time data
- Enable the Burn to ECU button so any table edits can be written back
Tip: If you are unsure which port to pick, try disconnecting the USB cable, note which ports disappear, then reconnect and select the one that reappears.
Baud rate
Most Speeduino and Megasquirt ECUs use 115200 baud. VETuner detects the rate automatically, but you can override it in Settings → Communication.
File-only mode (no ECU)
You do not need a physical ECU to use VETuner. If you have a VETuner Pro subscription you can load an MSQ tune file via Connection Setup → Load MSQ file to explore and edit your tune offline. Changes can be saved back to an MSQ file for later use.
ECU families supported
| ECU | Protocol |
|---|---|
| Speeduino (all variants) | Megasquirt serial |
| Megasquirt I / II / III | Megasquirt serial |
| MS3Pro | Megasquirt serial |
If your ECU is not listed but uses the Megasquirt serial protocol, load its .ini definition file manually via Connection Setup.
Troubleshooting
"Failed to open serial port" — Another application (e.g. TunerStudio) may already have the port open. Close it and try again.
No data after connecting — Check that the ECU is powered and the serial leads are connected correctly. Try a different baud rate in Settings.
ECU not recognised — Load the ECU's .ini file manually via Connection Setup → Load INI file.