Using reset pin of OEM EV inverter cpu to clear the way for external brain control

[amberwolf]

This post:
viewtopic.php?f=10&t=575&start=10#p7771
notes that it is possible to use the reset pin of the CPU of an OEM inverter to disable that cpu, to allow wiring in an external brain control, presumably without having to hack at the traces and wiring (as much, at least, and hopefully not at all) of the inverter/powerstage board.

Pin 124 of the TMS main processor is the reset pin called XRS. Pulling that to ground puts Elon asleep and leaves everything else up and running.

Most CPUs and other microcontrollers i've dealt with will tristate their i/o pins (at least the outputs) when held in reset, so they won't interfere with anything else that is on the same bus, etc. So this seems like the easiest and most reliable way forward; less risk of damaging anything else in the inverter while zombifying it prior to external brain installation.

My project (the SB Cruiser trike here https://www.endless-sphere.com/forums/v ... =2&t=67833 ) will be using a pair of Honda IMA inverters, more because of size than anything else, as I don't need the kind of power the larger inverters provide, and they should be significantly smaller and easier to use on my small trike than the others (though i face other challenges like weatherproofing). While i won't be using the Openinverter brain to control them (the Lebowski SMD brainboard instead), this technique should apply the same regardless of brain used. (The brain/inverter integration thread is here: https://endless-sphere.com/forums/viewt ... 0&t=105711 ).

I have been looking around for a week or so now, and not yet found which CPU the Honda IMA inverter uses, to then find a pinout for it, and thus locate the reset pin. Tomdb's posts over on DIYElectricCar forums here
https://www.diyelectriccar.com/forums/s ... p?t=163650
have some good pics of the insides, but the numbers are not readable on the CPU. I have a couple of the inverters on the way, and they should be here "soon" but with the covid19 stuff going on, there aren't any arrival time guarantees. So in the meantime I'm gathering as much information as I can, to speed up the process of developing the "system" to turn these into controllers i can use on my trike.


If anyone has any of that information handy, it would be helpful to me (and others that may also use this inverter) in going forward on this project.

The intent is to gather and document over on EndlessSphere and DIYElectricCar forums (and here on Openinverter if it's allowed, since it's a bit offtopic), all the information necessary for anyone with reasonable DIY skills to buy a brainboard (lebowski SMD specifically, but any of them in general to the degree I can) and a Honda IMA inverter (as they are very cheap) to make a good customizable/programmable controller for a small EV project.


If not, and assuming the pinout is not available anywhere once I do know what CPU it uses, I can probably locate the reset pin experimentally, using an oscilloscope to monitor a data or clock line (which might be obvious from component connections once i see it), and then grounding steady-state pins on the unit that are not Vcc/etc lines, until such signals are stopped, but resume when the grounding is removed.


(Note this thread is crossposted to DIYElectricCar forums as they have dealt with both the Honda IMA and the Lebowski brainboards, and might also have useful information. https://www.diyelectriccar.com/forums/s ... ost1055945
I also crossposted it to my "home" forum of Endless-Sphere, so that I can keep all the results there as well, for those that don't visit DIYEC or OI forums but want to do this sort of thing. https://endless-sphere.com/forums/vi...?f=30&t=105707 )

[MattsAwesomeStuff]

Hey, nice to see you over here.

For those that don't know, Amberwolf is a rockstar of the budget-built EV world, specifically, bicycles over at Endless Sphere. He seems to read almost every post and helps almost every person, in detail, with their project. He's coming up on an astonishing 30,000 posts in 10 years there.

Treat him well and help him out if you can.

... though, I don't have the answers, and, I haven't seen anyone here discuss Honda inverters. Toyota, Tesla, Nissan yes. :/

[amberwolf]

The inverters arrived, so the pin is now identified:
https://endless-sphere.com/forums/viewt ... 1#p1547401

Haven't got any further than that yet.

[tom91]

You found my pinout of the components to interface with then? It is quite a nice compact stage to work with.

I personally took the route of cutting the traces on the board and then soldering to the through hole pins.

[amberwolf]

Yes, your thread over on DIYEC was the first specific useful info I found when trying to decide which EV inverter I was going to go with for this project.

Kiwifiat and Coleeasterling are working on another version of the same kind of thing, to hopefully make a kind of "kit" if I understand correctly, to make these cheap and easy-to-find powerstages easy to re-use.

I'd rather leave as much of the original system intact as possible, for future experimentation possibilities, and so that I don't risk damaging things by slipping when cutting traces and such--I'm a fairly clumsy person, worse as I get older.

Holding the CPU in reset should keep it out of the way just as well as if it was removed from the board, or traces from it cut from components, and is undoable in one easy step.