Several people, including myself, have extracted useful data from their Prius by attaching a scanner to the OBDII port. These scanners consist of an adapter "dongle", a cable and software to run on a computer (notebook or hand-held). This is fine for enthusiasts who can part with the cost of these devices and are prepared to run a computer in the car. However, there are safety risks associated with this and even the best non-Toyota scanner cannot access interesting data such as the battery current and state of charge. Also, I never have the thing connected when something interesting happens.
Work by others beginning in April, 2003 started to uncover the messages the THHS (Toyota Hand-Held Scanner) uses to extract interesting but non-standard data from the Prius. My idea was to make this data (plus the OBDII standard data) accessible via a self-contained device that can live permanently in the car as a sort of auxiliary instrument panel. I wanted to keep the cost down so that it is affordable but I can make a bit of money on each one I sell to justify my time on assembly and the software.
These are the original goals I set for the Mini-Scanner and their state of achievement.
I wasn't far off with the parts cost, but with things like the connectors, the case, screws and spacers (which I had not taken into account in my initial guess) the cost crept up towards $60. My non-recurring costs (PCB design software, PCB manufacture, tools, shipping charges, etc.) came to about $400. Luckily, I was able to buy some Liquid Crystal Displays on eBay which saved $15 per unit. So, for the first 30 Mini-Scanners, I was able to meet my goal of $100 each. It takes about 90 minutes to assemble each unit. The software will take several hundred hours to reach the full functionality. So, in the end I might make minimum wage. But this is the most fun way to make minimum wage that I can think of!
Achieved. Version 0.20 has 24 selectable data items. Increasing this number will depend on work by others in snooping on THHS operation.
Achieved.
Planned.
Achieved, see photographs.
No out-and-out failures to install reported, but difficulty and time varies widely. The tricky part is threading the adapter cable behind the dash. This can be avoided if you don't want to conceal the cable.
Complete. I published a specification for this feature which met with general approval. Later, I wrote up the actual procedure for firmware (software) upgrades using a Flash Loader built into the Mini-Scanner. The "adapter" turned out to be a special serial cable, also usable for logging to a computer, and I set the cost at $7.00.
I have published information on what you need to write new firmware for the Mini-Scanner from scratch in the FAQ. The debug adapter for the ZiLOG software development tools is available as a zero-cost option. I plan to share enough of my source code for the Mini-Scanner so that people will be able to customize it.