VSS signal not being recognized?

[glug]

Oh, I see... The flip-flop to maintain state. I'll give that a shot.

Originally Posted by dcb

Why are you even commenting on the mpguino?!? It is painfully obvious you don't know how it works.

dcb, if you have some suggestions, or insight you'd care to share into the capability and preferences of the mpguino VSS input strategy, or a pointer to some docs, I'd love to hear them. Months ago, even - this thread started in March.

What has been *painfully obvious* for me is the crazy amount of time I've spent trying to get my reluctor vss signal recognized. I don't think this is an extreme corner-case. However, I am learning some new skills along the way, and that's good. ThoughI feel like I am re-inventing the wheel (!), plodding along in the dark, and the time I've spent has become a source of constant jokes from my friends. "Dude, why don't you just build an electric car. From scratch. It would take you less time."

Though, surely, without the help from Bob and Mike, I'd be toast.

[dcb]

Since you were building from scratch I was willing to let Bob try his hand at helping, but it is apparent he doesn't even know how the code works.

If you can find a lump of rotating metal, have a look at this thread. http://ecomodder.com/forum/showthrea...tml#post175454 It has been used successfully.

[bobski]

Originally Posted by dcb

It is painfully obvious you don't know how it works.

You either poll, or you use an interrupt. Since both interrupt inputs are dedicated on the single injector signal, it must be checked by polling. Whether the polling takes place at a specific point in code, is triggered by an event scheduler, or is triggered by a hardware timer-based interrupt is irrelevant. It's still time-limited and subject to the situation I believe we're seeing here.
Perhaps you could make some useful contribution to this thread by explaining why I'm wrong, rather than slinging defensive, derogatory comments.

Originally Posted by dcb

If you can find a lump of rotating metal, have a look at this thread. http://ecomodder.com/forum/showthrea...tml#post175454 It has been used successfully.

Better, but it still requires buying a ~$40 sensor, fabricating brackets and a pulse wheel and attaching it all to the vehicle. I would like to see the present approach succeed, as most (if not all) ABS-equipped vehicles use this setup to measure wheel speed.

[dcb]

http://opengauge.googlecode.com/svn/...no/mpguino.cpp

It is 100% open source, no need to pretend you know how it works, go look. It is not polling, I find that suggestion offensive especially when it is wrong.

[dcb]

Also, it is almost always more helpful to actually draw a schematic, with part numbers and values, rather than trying to explain it.

[bobski]

Originally Posted by dcb

go look.

I'm pretty sure I've expressed my dissatisfaction with the readability of the MPGuino code in the past.

Originally Posted by dcb

Also, it is almost always more helpful to actually draw a schematic, with part numbers and values, rather than trying to explain it.

Give a man a fish, or teach a man to fish?
D-Type Frequency Divider Circuit :: Radio-Electronics.Com

[dcb]

Did you type something? I decided not to read it. It must have been about Barry Manilow.

What do you know about the OP's signal? You've been screwing with him for 3 months now.

And let me clarify, when I say what do you know, I mean know. Not what do you imagine.

[glug]

Originally Posted by dcb

If you can find a lump of rotating metal, have a look at this thread. http://ecomodder.com/forum/showthrea...tml#post175454 It has been used successfully.

Thanks. That's an interesting thread. I recall reading it early on.

Unfortunately, I have a huge amount of time invested in tracing the wiring harness on my vehicle, searching for alternate vss sensors, combing the service manuals for information, searching under the dash for speedo signal driver boxes (that don't exist in my model year), etc. Documenting in the wiki that mpguino does not directly support reluctor output would be a great addition. If I'd known that early on, I might not have gone that route.

So what I have is a reluctor vss sensor located in the differential that has worked reliably for 170,000 miles. I'd rather not kludge up additional hardware. It should be possible to get this very nice sine wave into a TTL form that mpguino can parse. And the results of that effort should be useful to others.

Is the frequency limit of the VSS input known? My biggest concern is that everything I've been doing is pointless because the input can't handle the frequency I need - 10 pulses/mph, or 700 hz at 70 mph. That's 36,000 pulse/mile.

I've had a few circuits that output decent TTL, but all of them seem to hit a wall on frequency with mpguino. It could just be that my voltages weren't in the right range, etc.

[msc]

Are you still using the circuit that produces a short pulse at each zero crossing or did you change to the circuit that toggles the output for each zero crossing? I suspect you are bumping up against the MPGuino detecting ability.

The table on the wiki page has settings of 4000 to 16000 for pulse/mile on various cars. Yours being more then twice what anyone else has shown to work with any other car puts you in uncharted territory. I would divide your signal down to a frequency the MPGuino is known to work with.

I would use a dual flip flop to divide your pulse stream by 4. There are a wide range of options for doing this. Each flip flop can be used as a two to one divider and when they are cascaded you get a four to one divider. I would use a 74AHCT74 so you can take care of signal level matching and frequency reduction with the same part. The preset and clear lines get tied high and the following couple links show you how to connect the inputs and outputs to create various dividers.
Frequency Division using Flip-flops
background

I think your just a fifty cent logic chip away from success.

Mike

[glug]

I am using the circuit in figure 24 - it toggles the output at each zero crossing. And even with the voltage divider (3.5:1), I am limited to just over 200 hz or so.

What you suggest sounds like the best solution - just divide it into a range that is known to work. We're not doing ABS, so ultra-low resolution is not important. I'll order a couple of 74AHCT74's from digikey.

Though it still would be nice to go through the code and properly comment and document it. Anyone know if there is there a reason it isn't commented?