Adjustable Tach Output Signal?

[TheMonkey]

Not sure what changed in firmware. bumped up from 3.11 to 3.46 firmware on BMW M90 motor. Dash tach went from no problems on 3.11 to intermittent on 3.46. Drops out at a couple thousand RPM. No problems with tune or reving or tach dropouts, or datalogs.... just the dash tach drops to zero.

Is it possible to have some sort of adjustment to the signal to satisfy different OEM tach needs?

[grippo]

Yes there was a change. The previous tach signal was a fixed, very short active low pulse. Because someone had a problem with this being too short I changed it so that it puts out a 30% duty cycle, again active low. This fixed the problem but obviously broke your set up. So it looks like I need to make user tach inputs for either x% duty or fixed y us pw. While I am at it, I can limit baro readings to between 80 and 120 kPa.

[TheMonkey]

Great, thanks Al.

The unit that you will receive in a couple days will go back in BMW. If you don't have a chance to have user adjustable into firmware in the short term, just a hardcode back to where it was during 3.11 on this unit would be great.

In the meantime, I'll test it on an autometer tach - I'd bet your 3.46 changes work on that (where 3.11 did not).

On the baro limits.... I don't know if hard limits would be as helpful as a default for zero volts (unplugged) - pegging 2nd baro to something reasonable like 100, or maybe even revert back to initial map reading?

maybe both limits and a default 0v value?

[grippo]

Yeah you are right, it makes more sense to check for exceeding the limits as I said, but then setting to 100 kPa if it exceeds either limit. That will help many more people than the very few who are normally anywhere near either of the extremes. But on the other hand I don't want to make this totally innocuous, I want the user to say "something is wrong", because there is and they should know that, but I don't want them stranded on the roadside trying to figure it out.

[TheMonkey]

... I don't want to make this totally innocuous, I want the user to say "something is wrong"..

the same could be said for CLT and IAT. it defaults to innocuous, which i like because i can get home - but need a heads up.

perhaps the answer is to default to innocuous, but have some sort of check engine light equivalent. can one of the LED lights be used for this purpose?

i actually wanted to set up one of them to be lit during wasted spark, then go dark at sequential - just to make sure cam syncs. but would be even better to program a light to be on during cranking, and then only stay on if an error condition is met (baro2, iat, or clt = 0v, or remains in wasted, etc...)

edited to add: error light should include TPS & o2 at 0v, or other error condition.

[grippo]

OK, here is a new code version and ini file. It has the following changes:

1. 2 new inputs for the tach output: a fixed PW input and a duty cycle. In general you want to set one of these to 0 and use the other, but in theory you could use both. You can set them from the ignition menu/ tach output submenu.

2. Baro is limited to be between 80 and 120 kPa. If outside these limits, it is set to 100.

[TheMonkey]

Nice!

Is there a way for me to read the code in the 3.47 abs file? I'd just be interested to see the logic, but it's just a bunch of letters, symbols, and numbers when i open in notepad.

There isn't anything for me to do with that abs file is there? isn't that the file that you load onto sequencer with your special BDM cable hardware?

[TheMonkey]

Al-

In an earlier post, Bruce had posted that the original beta tach output was 150 micro seconds.

The new code looks like the input is in milliseconds (ms)? I just want to confirm, that to program so that 3.47 outputs the like the original settings, I would set it to: TachOut Fixed = 0.15 and TachOut dutycycle = 0 ?

Thx, Scott.

[grippo]

The tach output is not an exact pw - to get to the us level requires using processor resources that have been used up for more important stuff like fuel and spark. So the min pw is 0.2 ms and this may end up varying between .1 and .2 ms, but this should be way better than what you have now, which is a 30% duty cycle. (Note you can enter .1 or 0 pw if you want, but it will end up as 0 and if duty is also 0, you will probably get sporadic output.) So try 0.20 ms and 0% duty and see if that works.

Also I found that the ini file doesn't provide for a decimal place, so I have fixed it for that and a new version is attached.

[TheMonkey]

Bingo-

3.47 set to fixed pw on tach output works on the BMW, but not Pontiac with Autometer tach. When it's set to duty cycle, it works on Pontiac with Autometer tach, but not BMW.

Nice fix.