The MegaSquirt3/Pro and Speeduino/SpeedyEFI all use the same binary.
Speeduino specific Instructions.
1. Download the .zip file here..
2. Use AVRDUDESS to upload the .hex file to the Arduino Mega. Click here for instructions.
4. Go to Speeduino’s wiki and ensure Secondary Serial IO is enabled.
5. Press the SHIFT LIGHT and CONFIGURE your ECU, Warning lights and DEFAULT Layout. If you dont, the dash will not function properly. At the time of this writing, I may create defaults if there are none. Double check them.