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-   -   VSS signal not being recognized? (https://ecomodder.com/forum/showthread.php/vss-signal-not-being-recognized-16518.html)

glug 03-20-2011 11:23 AM

VSS signal not being recognized?
 
I'm really impressed with mpguino. Thanks to everyone who has made it happen! I am so close to having my own duemilanove build working, but I need some help..

The snag is the VSS signal. I have verified that I am getting a nice, clean sine wave (at all speeds, at least up to the 35mph I have tested), but it seems it isn't being properly processed. It only starts to register VSS at speeds above 35 mph, and then increases too rapidly.

I think there is something wrong with the behavior of the VSS code as it relates to my signal. The injector pulse width measurement seems fine. I am debugging with the serial port output.

This is my second build. The first was on breadboard, and it had the same problem. My initial build had 100K resistors, and I assumed that was the issue. My perfboard version has 50K. I feel that the circuit is correct.

I am running mpguino.pde version 0.75 with arduino 022. I assume that is okay due to the at328. I tried the "required" 0011, but this sketch is too large to compile, and that version does not support the at328. I also tried 0016.

I have recorded (on an audio recorder) the VSS sensor output - both the raw sensor output, and also at pin 14/0 (after the resistor and diode). It's a great looking sine wave of approximately 10 hz per mph (approximately 36,000 pulse/mile). When sampling at pin 0, the bottom of the waveform is a bit flattened.

I considered that my arduino may have a bad pin 0, so I tried another duemilanove with the same result. Other code is reading signals on pin 0 just fine.

At rest, the sensor has an impedance of 1.25K.

The vehicle is a 1990 Ford F-250 truck, and my VSS source is the "RABS" sensor in the differential.

I have tried a variety of pulse/mile settings. At this point, I'm not sure where to go next. I know the vss code is quite mature, so I don't think I should need to tear into it.

Thanks!

glug 03-28-2011 11:50 AM

I'm still stuck and could really use some help. I'm not sure what to try next.

What could this be? Grasping at straws - bad diode? A simple in-circuit ohm test with a DMM shows them blocking in one direction. In the other, the INJ is 3.77 Mohm, and the vss is 4.06 Mohm (that is with the arduino and vehicle connections disconnected from my perf board).

bobski 03-28-2011 07:38 PM

Well for starters, the signal is supposed to be a square wave rather than a sine. ABS sensors tend to be simple coil-and-magnet setups that read a notched ring that spins with the axle. The VSSs that others have been using are switch-type sensors or have internal driving electronics that output a clean square wave. Is there a VSS sensor somewhere that isn't a part of the ABS system?
If not, an op-amp could turn your sine into a nice square wave.

glug 03-29-2011 09:39 AM

Thank you, Bob. That is very helpful, and does explain things.

There is another sensor, on the E40D transmission. However, I believe it is also a variable reluctance type of sensor that produces an a/c output. This truck has a mechanical speedometer. In '92, the trucks include a PSOM module that converted the differential VSS signal into something more appropriate for the electronic speedo and odometer. It also downsampled to 8000 pulses/mile.

So I need to process this signal. I found the LM1815. It looks nice, but I would need to order that. I've found a few circuits that might work, but not any that included a success story. Still looking, suggestions appreciated. Especially for 'shackable designs that won't require an order.

It'd be nice if we had an example of a working circuit in the wiki.

bobski 03-29-2011 10:15 AM

Ah yes, reluctor ring... That's the term I was looking for.
The LM1815 looks nice, though a tad pricey at $4 a piece +shipping. On the other hand, application-specific circuits tend to be less buggy and longer lived than something cobbled together, especially in automotive applications. I would also be worried about the electrical characteristics of a custom-made circuit. If it doesn't have enough input impedance, it could drag down the sensor signal and interfere with whatever else is using it. That shouldn't be a problem with an op-amp, but be careful with any kind of signal conditioning you might use to protect the amp's input.

glug 03-30-2011 12:28 PM

1 Attachment(s)
I can't help but wonder whether this could be done in software, maybe with limited hardware help. It'd be helpful if the existing code had more comments. They don't use any memory ;)

I am thinking of trying this circuit, and wondering if it will work. It is from this thread:

Sine to square wave using op-amp - Page 2 - All About Circuits Forum

glug 03-31-2011 12:34 PM

I tried that circuit yesterday, and drove it with the sound output of my laptop. The results weren't optimal - still a sine wave. Perhaps there was not enough gain in the circuit. It is also possible my laptop output was too weak.

I also tried a 741 based design I saw in a book while buying parts at the 'shack. Similar result. The schematics I see tend to be speculative, and not tested with automotive reluctors. It'd be easier if I had a scope, but even then, I'm not much of a hardware guy in regard to developing the circuit.

So I'm still not MPGuinoing :(

glug 03-31-2011 02:26 PM

I just re-tested the schematic posted above and the results were more encouraging. In the initial test, my laptop audio outputs weren't turned up all the way. Sure enough, the results improved with the output higher. Though the low speed output from the sensor is a bit low voltage, so that may be a concern.

The output is much closer to a square wave. However, at lower hz, I am getting sloped peaks, not flat. I guess I'll have to drive it with the actual sensor and record it again.

The square wave output is still very much a/c. Should I try and sink the negative component with a diode? Or is the zener in the MPG circuit going to take care of that?

bobski 03-31-2011 03:39 PM

Quote:

Originally Posted by glug (Post 229054)
Or is the zener in the MPG circuit going to take care of that?

More or less. It should clamp the input to around -0.5 volts. A plain rectifier diode between your circuit and the mpguino should clean that up, but might affect low speed sensitivity.
If you're still seeing a sine wave on your circuit output, the amp isn't giving you enough gain. It should be so heavily amplified that the output is swinging from clipping negative to clipping positive with an almost immeasurably steep slope at the crossings. If you were using a single supply op-amp, that would be VCC and ground (or very near it) in response to 0V crossings on your sensor input.

glug 04-12-2011 10:53 AM

1 Attachment(s)
Thanks, Bob.

After bench testing three different circuit types, I finally settled on an lm339 based comparator (see below). Bench testing a breadboard version went well. An audio sine wave produced a TTL signal that the mpguino could track up until 488 hz. Though that is not enough - my truck vss produces 10hz per mph. So that is only 48 mph. I considered that it might be related to the perfboard layout, or perhaps my ttl isn't ideal.

I added the circuit to my perfboard, but the in-vehicle tests were a disappointment. I am apparently getting interference/feedback from within the mpguino circuit. I suspect the lcd driver is sending pulses into the ttl driver. My mph climbs, but then stays elevated at 25 or 40 mph - even after the ignition is shut off and the vss and inj inputs are disconnected from the mpguino.

So I think the next step is to cut the perfboard to separate the sine2ttl circuit from the rest of the mpguino. Any suggestions on other steps, like circuit mods, to otherwise improve the situation would be appreciated.

bobski 04-12-2011 12:24 PM

Quote:

Originally Posted by glug (Post 231108)
I finally settled on an lm339 based comparator

339, or 393? Though it's a pretty basic comparator circuit that should work with many op-amps, your diagram says 393.
10uF might be overkill for the decoupling cap on your input. Also, electrolytic caps are polarized, and I think the polarity is backwards in that diagram. Try turning the cap around and/or a mylar cap (or something else unpolarized in the fraction-of-a-uF range) and see if that helps with limitations you're seeing.

glug 04-12-2011 02:27 PM

Thanks again, Bob!

I couldn't find a 393 locally, so substituted the lm339 from rat shack. It seemed a reasonable substitution. And yes, the polarity for C1 on the posted schematic is wrong, and it is correct in my circuit. I should have corrected that before re-posting it.

I'll try a smaller cap, thanks for the suggestion. I can see how that might be a factor.

glug 04-12-2011 07:48 PM

I replaced the electrolytic with a .1uF polyester film...

When generating a controlled sine wave input, mpguino VSS pulses track well between 30hz to 130hz while the LCD is removed. With the LCD plugged in, there seems to be some additional noise in the VSS.

Below 30hz, there are spurious pulses. That isn't a huge concern, since my VSS is 10hz per MPH. Above 130 hz, I start to lose pulses. So, barring other ideas, it seems the next step is to carve the TTL circuit out of my somewhat spaghetti perfboard.

75mph is 750hz... So I do need to significantly improve the situation.

Fwiw, the injector pulse figures I see while in the truck look good.

bobski 04-12-2011 08:03 PM

Can you set up a 555 circuit (or a function generator if you have one) to give you a nice, clean square wave? It would be nice to rule out software limitations.

msc 04-22-2011 11:59 PM

The LM2907 is a low cost frequency to voltage converter that works also works great for interfacing to a variable reluctance transducer. It comes in a couple variations. The 8 pin part has all the signals necessary for this application.

Search digikey.com for LM2907 then download the data sheet. At the bottom of page 12 in the data sheet there is an example circuit for this application.

Mike

bobski 04-23-2011 12:34 AM

Quote:

Originally Posted by msc (Post 233423)
The LM2907 is a low cost frequency to voltage converter that works also works great for interfacing to a variable reluctance transducer.

Good call.

glug 04-27-2011 11:46 PM

Thanks for that suggestion, Mike. That looks like a good solution. Oddly, I had saved that data sheet back on may 7, 2009 - probably for similar reasons.

I still need to follow Bob's advice and verify the TTL measurement capability of my circuit. I don't have a signal generator, so I intend on driving it with another arduino and the tone library. Just haven't found the time, and I needed to take a break from it for a while.

bobski 04-28-2011 12:12 AM

Quote:

Originally Posted by glug (Post 234625)
Just haven't found the time, and I needed to take a break from it for a while.

I hear ya. I got one of those rack-of-bins things from harbor freight just to keep all my projects sorted out. I work on one until my attention wavers or I run out of free time, then it (and any associated parts) goes back in its bin until I feel like working on it again. Before I started sorting it all out like this, my bench was constantly 6" deep in cables, half-disassembled electronic devices, bare PCB boards, stripped wire insulation, clipped component leads and half a pound of assorted hardware. I would constantly set my safety glasses down and lose them in the clutter. Not buried or anything... Just hidden in plain sight.

glug 05-01-2011 01:14 PM

Quote:

Originally Posted by bobski (Post 234627)
Before I started sorting it all out like this, my bench was constantly 6" deep in cables, half-disassembled electronic devices, bare PCB boards, stripped wire insulation, clipped component leads and half a pound of assorted hardware. I would constantly set my safety glasses down and lose them in the clutter. Not buried or anything... Just hidden in plain sight.

If only someone would invent cordless dvm probes, I'd be free of their tangles...

Of course, then I wouldn't be able to find them by following the leads.

glug 06-07-2011 04:14 PM

1 Attachment(s)
I finally have an LM2907 in hand, and I'm ready to make this thing work... I'd like to cut down on the experimenting, so suggestions are appreciated.

The application note shows two circuits which seem to be appropriate (reproduced below, figure 23, from the top of page 14):

http://www.national.com/an/AN/AN-162.pdf

Any thoughts on which of those would be the best match for the MPG's VSS input?

The first circuit outputs pulses at 5v, and is also a frequency doubler (two-shot). The other other is a one-shot, and outputs a square wave of about 2.5v. Another gotcha - digi-key did not have the through hole 500nF cap needed for the first circuit. I have a 1000nF.

My VSS is about 10 pulse/mph, for 36K pulse/mile. So 70 mph is 700 Hz. Would 1400 hz be too high for the MPG input?

Since my proto mpg perf board is now a bit cluttered, I am planning on building this on a small sub-board.

Thanks!



From the AN:

Digital Interface
A growing proportion of the complex control systems today
are being controlled by microprocessors and other digital
devices Frequently they require inputs to indicate position
or time from some mechanical input The LM2907 can be
used to provide zero crossing datum to a digital system us-
ng the circuits illustrated in Figure 23 At each zero crossing
of the input signal the charge pump changes the state of
capacitor C1 and provides a one-shot pulse into the zener
diode at pin 3 The width of this pulse is controlled by the
nternal current of pin 2 and the size of capacitor C1 as well
as by the supply voltage Since a pulse is generated by each
zero crossing of the input signal we call this a ``two-shot''
nstead of a ``one-shot'' device and this can be used for
doubling the frequency that is presented to the microproc-
essor control system If frequency doubling is not required
and a square wave output is preferred the circuit of Figure
4 can be employed In this case the output swing is the
same as the swing on pin 2 which is a swing of half supply
voltage starting at 1 VBE below one quarter of supply and
going to 1 VBE below three-quarters of supply This can be
ncreased up to the full output swing capability by reducing
or removing the negative feedback around the op amp

glug 06-07-2011 10:34 PM

I just did a breadboard test of circuit #1 with the 2907. I used the 1000pF cap.

The results were very similar to those from my previous TTL circuit.

On my test bench setup, the pulse rate reported from the arduino USB port tracked the sine wave frequency exactly 1:1 until 189 hz. At that point the arduino pulse rate would go no higher. And when the sine wave frequency passed 283 hz, the arduino pulse rate started to decrease.

This is a tiny breadboard with fairly short leads.

Any suggestions?

bobski 06-07-2011 11:21 PM

Try the second one? ^_^

msc 06-07-2011 11:45 PM

Either should work but I would go with the second one (fig 24). I don't know the limit but the VSS input may miss pulses that are two short. Mostly guessing on that but I know the interrupts are in use for the injector input so there may be limits to what the VSS input can detect.

The 5 volt source may be a little low for the LM2907. The max voltage is 28 volts. I didn't see a minimum voltage but the performance graphs only went down to 6 volts. I would just power it directly off the battery voltage.

It looks like the low part of the signal may not be low enough for the arduino input so it may be necessary to add a resistor to form a voltage divider on the input. The logic levels required are very low, less then 0.2 volts for low and anything over 1.0 volt is read as high.

When you get the circuit built you can toggle the output to low and read the voltage. If the low voltage is less then about 1.3 volts it can be divided down with resistors. If the low voltage level is higher then that a FET and a resistor can be used to give you a signal that goes very close to ground. A wide range of logic gates could also be used for level matching if that's what you have laying around.

Mike

bobski 06-08-2011 12:56 AM

Quote:

Originally Posted by msc (Post 243736)
VSS input may miss pulses that are two short.

Yeah, that makes sense to me. I was thinking earlier that it's like the VSS routine is missing pulses - pulses are starting and ending before the routine gets called. That would happen at very high frequencies if you were feeding it a plain square wave. Since this circuit outputs short pulses, it's easier for the guino's VSS routine to miss the detection window.

Quote:

Originally Posted by msc (Post 243736)
A wide range of logic gates could also be used for level matching if that's what you have laying around.

A flip-flop would be perfect with that frequency doubling circuit. Wire it up to toggle on each clock rising edge, then feed your circuit's output to the clock pin. The flip-flop will act as a frequency divider, so you'll get the proper number of pulses out in a nice 50% duty cycle square wave.

glug 06-08-2011 10:23 PM

Quote:

Originally Posted by bobski (Post 243731)
Try the second one? ^_^

Brilliant! :P

I just wired it up and got to 240 hz on the mpg. So it is an improvement. Now I need to follow Mike's suggestions, and tune it a bit.

Thanks!

glug 06-10-2011 10:47 AM

So, I'm a bit stuck on what I can do to improve this situation. An assumption is that lengthening the pulse duration will help with detection. I'm wondering how to do that. Halving the frequency with a flip-flop will help, but that will only get me to about 48mph - not nearly enough.

I will try increasing the supply voltage, but I'm not sure that will improve the mpguino pulse detection. There is also the gotcha of prototyping on an arduino and not having conditioned 12v to feed it. So I plan on testing it with a 9v to see whether the frequency capability can be increased. Though that does not seem to be the limitation. I eventually intend to dedicate an atmega to this, and free up the arduino. But only after it is working well.

If I had a signal generator and scope, I'd profile and document the capabiliy of the mpguino's VSS input. As Mike mentioned, that it isn't interrupt driven raises some questions about the capability. I did some testing with the arduino tone library, but the results weren't very encouraging. I need to revisit that (as well as developing better siggen capability), but it seems like a distraction from getting my mpguino working.

msc 06-14-2011 12:06 AM

I had a chance to play with an LM2907 circuit on the bench. The circuit I had laying around to play with was the circuit (fig. 24) right out of the app note with the addition of some input protection components and a 30K load.

I tested the circuit as low as 3 volts so 5 volt operation should be fine.

Being careful to adjust the input signal so there were zero crossings to detect I was able to detect a signal as low as 6mv P-P. The ability to detect the small signal as the speed approaches zero is the prime reason for using this part.

Some voltages I measured for output high and low at different excitation voltages: (5V exc, low 0.84V, high 3.08V), (12V exc, low 2.44V, high 8.50V), (14V exc, low 2.94V, high 9.98V). I expect these levels can vary a bit form one chip to the next so your mileage may vary.

From the data sheet for the ATmega the logic thresholds for 5V operation are max voltage for low is 0.3V and the min voltage for high is 0.6V. So this confirms your problem is a miss match of logic levels. You just need to get the low logic level low enough for the ATmega chip to see it as low.

The following suggestions assume you are powering the LM2907 with 5 volts.

A simple voltage divider of about 3:1 or 4:1 on the output of the LM2907 should do the job. A 10K and 20K resistor would be about right for a 3:1 divider. A 10K and 30K resistor will give you a 4:1 divider. Be sure to take into account or remove the input pull down resistor if present on the VSS input.

Another approach would be to use a pull up resistor on the VSS input and a FET to switch it to ground. The Gate input of the FET would be driven by the LM2907 output. You would want to select a FET that is 3.3V logic compatible, the gate threshold voltage should be around 2.0 to 2.5 volts.

A logic chip from the 74AHCT family would work as well. 74AHCT04 inverter would be a good choice but AND, NAND, OR, NOR and others can be used by tying other inputs high or low as appropriate. The AHCT logic chips have input thresholds of 2.0V for high and 0.8V for low. The output levels are 4.5V for high and 0.1V for low.

Mike

glug 06-17-2011 10:57 AM

Mike, thank you for the help!

I see now the importance of the logic output level - I hadn't realized it might vary with input level.

I mocked up the voltage divider and did some bench tests. However, my sound card signal generator is voltage limited. The a/c voltage does not increase like the actual reluctor.

Even with the divider, I was still limited to about 240hz. And if I push the input frequency higher, the mpguino reported pulse rate rapidly drops.

So I'm still puzzled. Are my peak pulses too low, my lows too high, or is there another issue with pulse detection at that rate, perhaps software?

I may try and go back to using a spare arduino to generate logic pulses in order to verify that the mpguino can actually detect at the necessary rate.

bobski 06-17-2011 11:23 AM

Have you tried a flip-flop yet? The MPGuino uses a polling strategy to watch the VSS input, meaning it only checks the status of the input at regular intervals. If a pulse from your circuit starts and ends before that interval comes around in code execution, the MPGuino will miss the pulse. The shorter the pulse, the easier it is for the code to miss it. A flip-flop doesn't have any such limitation and will convert the signal to a 1/2 frequency, 50% duty cycle square wave, very much like a standard switching VSS.

dcb 06-17-2011 11:51 AM

Quote:

Originally Posted by bobski (Post 245620)
The MPGuino uses a polling strategy to watch the VSS input, meaning it only checks the status of the input at regular intervals...

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

glug 06-17-2011 12:27 PM

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

Quote:

Originally Posted by dcb (Post 245623)
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 06-17-2011 12:58 PM

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 06-17-2011 03:46 PM

Quote:

Originally Posted by dcb (Post 245623)
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.

Quote:

Originally Posted by dcb (Post 245631)
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 06-17-2011 04:02 PM

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 06-17-2011 04:35 PM

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

bobski 06-17-2011 08:52 PM

Quote:

Originally Posted by dcb (Post 245660)
go look.

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

Quote:

Originally Posted by dcb (Post 245662)
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 06-17-2011 09:18 PM

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 06-18-2011 09:23 AM

Quote:

Originally Posted by dcb (Post 245631)
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 06-18-2011 03:20 PM

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 06-18-2011 06:59 PM

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?


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