From Autosport Labs
USB to Serial Adapters
Typical problems with USB to Serial chipset
Double-check functionality with a known-good environment
It's always good to ensure the equipment you're communicating with (Megajolt, etc.) actually works in a known good environment. The best way to do this is to remove the device in question from the vehicle, power it up on the bench with a fresh 9V battery (or equivalent), and test it with a computer with a built-in serial port.
Once you can establish this base-line, you can move on to troubleshooting other aspects of the installation.
Interference issues with running engine
Some USB-Serial chipsets are especially sensitive to the high voltage spikes emitted from the ignition system. If timeout/communication errors occur after the engine is started, try:
- Moving the adapter away from the suspected hostile environment using a serial extension cable
- Replace plug-wires
- Check ground connections on components (use a star-grounding pattern)
- If the laptop is plugged in to the vehicle (either 12V or an AC inverter) try running the laptop off of it's internal battery
- Try a different USB-Serial adapter
Application and/or windows crashing
Problems with the adapter's device driver software can cause the software application to crash, or worse, cause the Operating System to crash (Blue Screen on Windows). If this happens frequently, look for an updated device driver from the manufacturer.
Adapters and chipset technologies
Note, the images below are representative and may not match actual hardware. It seems there are endless variants of this technology- if you find new information, please contribute to this page.
These are commonly found in low cost adapters.
Also found in low-cost adapters. These adapters posed a problem with earlier versions of the Megajolt Lite Jr. Software, but changes in the latest software corrected issues around this adapter.