VSS help please

[Addicted]

Lance et al,

I've spent a lot of time now trying to sort out my VSS signal, I've also tried to avoid asking for help on here, but I'm at the end of my tether now and need a kick..

My VSS sensor is an 8 pole magnet and reed switch (Audi OEM). It is wired to the Megashift via the OEM twisted pair, shielded cable and the shield is grounded at Pin 17. The power ground is via two other pins and is connected directly to the engine ground (all OEM). The power to the reed switch is 12v taken from the megashift board, so the input circuit is seeing a 12v square wave (verified on the 'scope)

The datalog attached has input masking @85% and smoothing factor at 10 (attached msq now shows 12)

Increasing the smoothing factor does appear to have reduced the amplitude of the noise, but not enough.

Looking at the datalog and msq is there anything glaring that stands out to be altered as I can no longer see the wood for the trees.

Maybe there's a input circuit better suited to receiving a 12v square wave?

Any pointers would be gratefully accepted.

Martin

[Bernard Fife]

Martin,

I have spent several weeks on some extensively re-worked 5.xxx code that may help. It completely redoes timer interrupts (and also adds the new crc32 serial envelope comms). This should help with some hard to diagnose issues like erratic speedos. I am in the middle of rebuilding my test bench though, so it will be a day or two before I can test it and post it on the site. If you want to try an early draft version very, very cautiously, I can post it here (bearing in mind it might not work at all at the moment, but it will soon).

[Addicted]

Hi Lance,

I can wait a few days if it would help, the car isn't going anywhere right now

Martin

[Bernard Fife]

Maritn,

Great, I will post draft code here once I have a chance to do some rudimentary tests.

[thatswagenwagen]

Addicted,

I cannot really help all too much with my VR snesor, but with changing R59 and R45 really helped me out a lot. I increased the 300K to 400K and increased the 10K to 47K and my speedo is almost perfect now at 65% .. Just a thought.

Sam

[zen]

hi

ok not using reed switch but oe zf24 vss sensor..nothing i did with hardware or software would sort vss out..to the extent it killed both diffs when lost signal..

however the lm2907 seems to be the cure for me atleast..killed all the noise..it is cheap..rs components sell over here (uk) you dont need the optocoupler as shown on this forum somewhere, just 5v zenor clamping (just in case) and resistive p.d.on the output .

has turned my unuseable vss into rock steady at , well over 150mph...(tested using low range in tranferbox, so flatout in 4th indicated 150+)

no reason why wont clean up a squaree wave!?? took 30mins to make ugly bug style on copper clad..whats to lose??

[Addicted]

Hi Zen, thanks for that..

I was thinking of simply changing the supply voltage to the reed switch from 12v to 5v, feeding the output into an optocoupler (that I have in stock) and feeding the output to the processor, pretty much the same as the hall ignition input circuit used by megasquirt.. I don't know how Lance has the interupts in software, but the output from my opto should work just the same as the output from the existing VR conditioning circuit..

[tobmag]

Seems like the VSS is the main issue for most users.

I ended up with this fix for my 4L80E tranny , this replaces the onboard VR circuit

viewtopic.php?f=4&t=678&start=30

BR//Tobmag

[Addicted]

Maritn,

Great, I will post draft code here once I have a chance to do some rudimentary tests.

Lance.

How are you getting on with this Lance?

[Bernard Fife]

Addicted,

If you want to try some early code, here is 5.090:

Monitor_5090.abs.s19

(77.56 KiB) Downloaded 1520 times

GPIO_MShift_5090.ini

(255.38 KiB) Downloaded 1538 times

This code has extensive changes to the interrupts that should help clear up some VSS issues (and a number of other changes).

This code hasn't been as extensively tested as I would like (due mostly to issues with my test bench). However, things like the speedo, auto/manual shifting, solenoid control, serial comms, CAN comms, LEDs, etc. all appear to work. So use a lot of caution, and be prepared to switch back to the original code at any time.

5.090 won't be going up on the beta web page. That will be updated with later code (5.091?) once I have been able to do more testing.

BTW, the 5.09x+ code will have a 'sister code' numbered 6.09x+. 5.09x+ will use the old style comms, and 6.09x+ will use the new serial envelope format with CRC32 message checking. The 6.xxx series code is intended for use with 3.83x B&G code and any extra code that uses he new format. However, I won't release the 6.09x+ code until the 5.09x+ code is better tested.

This code also has a new user setting for the highest gear for burnout mode. This is active in auto mode. It lets a user specify a gear lever position, and any time the gear lever is in that position or lower, the target gear will be the gear lever position. For example, if you had a 4-speed transmission, and set the "Burnout Mode Highest Gear" to 3 (under Shift Factors), then the trans would act as an normal automatic, and use gear 1st through 4th, if the lever was in 4th (aka. Drive/OD/etc.) and if the lever was in 3rd the target gear would always be 3rd (rev limiting, hysteresis, etc., still applies). And the target gear would always be 2nd if the lever was in 2nd, etc.