I’m officially working on a new revision of the board, with a few changes.
First are the obvious fixes, the ISP connector, pull-down resistors, etc.
But there’s a fundamental thing I want to change.
My car appears to have a bad connection somewhere. I haven’t been able to track it down yet. Somewhere, there’s a bad ground or something. Likely a result of the horrific radio install from the previous owner. Once before, my car has had an issue where the power flickered for a second while I was driving. This wasn’t a big deal at the time, as my radio just rebooted, and my headlights flickered for a partial second. I went on my merry way.
However, it happened again. With CaRFID installed. This happened over a week ago, but it took me a while to dissect what happened, and to calm down enough to actually write about it. It’s a bit embarrassing too, to be honest.
I was driving on a US highway (US-136), heading back to college, going 60mph (speed limit) on a dark part of the highway, deep in cornfields (at about 10pm). I turned a corner, then suddenly my entire car went dark. The power seems to have flickered, which knocked the ignition out completely, which caused my headlights to turn out, leaving me in pitch black. The engine cut out as well. I kept my wheel straight and carefully applied the brake in pitch black. Thankfully I didn’t go off the road. Turning my hazards on and pushing the car off the road, I got to work on getting it running again. I tried simply re-authenticating, but it didn’t crank over, in the same way it would if the transponder bypass wasn’t working.
I believe two events happened over the single drive. The first was the antenna shifted for the bypass. It moved out of the zone where it could get a good couple. I have it jammed in there somewhat awkwardly, so it’s not a huge surprise. The second event was the power flicker, which caused a full deauthentication.
After panicking for a bit, I managed to figure it out, and get the antenna put back in a position where it worked. I’ve been carrying all of the tools needed to take apart my center console, in case this happened (thankfully my ignition isn’t on my steering area, it’s by my radio).
This ordeal shocked me, as I had put over 10 hours of highway driving on as a test, with no issues. I even drove to a neighboring state after each significant change.
I was originally going to implement latching relays (or a latching circuit) as a safety feature, for the RUN and KEY_INSERT positions. I decided not to, due to the considerable cost increase for components, combined with the extra pins needed on the MCU. The new version is 1000000% getting 2 latching relays for those positions. My thought pattern was that other aftermarket push button starts don’t implement latching relays, so it must not be a big issue for most vehicles. I was wrong.
I’m lucky to be alive, to be honest. If it had cut out a few moments earlier, I might have veered off the road at full speed. I got passed by a few people before I got my vehicle pulled off the road, if someone hadn’t seen me, they would have hit me going 60+.
Learn from my mistakes here. Don’t sacrifice safety, even if you think you’ll be fine. In 99% of vehicles this wouldn’t be an issue, it was an issue of compounding errors, but it was still reckless. It was legitimately terrifying, and it took me a full day to stop shaking. Having to drive another hour afterwards wasn’t great either.
The second I can, I’m going to sure up the power connections to the board to the best of my ability, I’m considering even bodging some kind of secondary power, until I can get a new revision fabricated and assembled.
I’ve attached a video of my dashcam footage from the incident. Thought it would be interesting for everyone to see, at the very least. Ignore the incorrect date, my dashcam needs replaced (the internal rechargeable backup battery is failing, date resets every drive).