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0-12V did not work.

Mkay....

It may have worked had I passed it through a capacitor like I did the 0-5V lines, however I haven't tried that yet.

The MAX232 works like a champ. I may revise it in the future with the suggested mods if I have good luck testing them.

Would OBD0 simulation software be possible with just a software change?

In theory, yes. I haven't examined the waveforms on OBD 0, but I would assume they cross zero in a similar fashion. I talked to Dave, and he confirmed that the crank trigger wheels have a different number of teeth, so yes a software change would be required.

A perfect reason for the upgradeable firmware

I got your upgradable firmware right here:



$30

I think its a small price to pay for the guys who are serious about changing it up.

If I were to implement a bootloader, you would have to use a Hulog to load the firmware. It probably wouldn't be that bad really.

Maybe I'll get adventurous on saturday...

Hey any pics of the finished product in it's case or will the final version be released as shown?

Yes, its just a different pattern.
I can simulate on my test bench both, OBD0 and OBD1 distributors with the same hardware but different tables for the different signal pattern.

Nice. In the idea of keeping it plug and play, perhaps I can make a version with OBD 0 firmware/connectors.

i know you have a lot of projects on your hands, but this gave me an idea for a product that might be popular:

a translator for the honda ECU that can read cam/crank triggers from other engines and output what the honda ECU needs to see, allowing the use of the obd1 ecu as a standalone EMS for other cars. it would make using it a lot easier than grafting the honda distributor onto the head like we've been doing thus far. the engine bay in my MR2 is tight enough without the huge accord distributor hanging off the head.

just thinking out loud mostly. like i said, eventually i want to switch over to a pair of crank triggers and a cam trigger and go distributorless. i'm not an EE though, so it's taking me longer to finish the design for the ignition multiplexer than i'd hoped.

i'm still trying to figure this out though. the signal crosses zero twice per cycle- once when it dips below ground as the tooth approaches (downward slope), and the spike when the tooth passes the sensor and moves away.

on the scope pics you and doc posted, does the ECU trigger on the rising or falling edge of the signal?

i'm trying to work out the phasing between the teeth so i can make up a crank trigger wheel.

That's a good question. I don't specifically know about your application, but there may be an easy way to find out.

I traced the VR signal through the ECU until it hit the board that actually turns it into the 0-5V wave. Then I probed every connection on the board until I found the corresponding TTL level signal. I noticed that when I didn't apply a waveform, this line sits at 5V. For me that's enough to say that it (in all likelihood) triggers on a negative slope. However, it is very possible that the board actually inverts the signal. I don't remember at this moment if the OBD I ECU actually did this, but it is very possible.

excellent idea. i'll have to wait a few weeks until i fire the car up again. we had wind chills of -25 last night, and i aint going outside to the garage for any reason. i mean, it's march for christ sake!

i think you're probably right about the falling edge. the falling edges on the graphs posted seem to most closely coincide with the tooth spacing in the distributor.

i wonder if it's possible to send a direct input to those board connections through a buffer and bypass the VR board completely.

I'm sure of it.

When I couldn't get the amplitude I needed out of my "sinusoid" I thought about doing just that, but I'm limited by the constraint of wanting to offer a 100% plug and play product.

For the record, I do think that a 0-12V square wave passed through series capacitor would have probably worked. I haven't tested it or anything, but I'm fairly confident that it would've worked just fine instead of the MAX232.