IAC tuning. Am I crazy? (Solved!)

Post by **grippo** » Tue May 09, 2006 9:24 am

OK we have come up with something else to try, although it still doesn't explain why some units work, some don't. The command to move a step is given by reading a register, immediately changing the bit for the IAC channel, and writing it back out. This is done for each of the 2 IAC channels. Once the register is read nothing can change it (if I am not in an interrupt , I lock out interrupts.) However, the manual for this chip shows 2 registers that can be read. One is the register value that is supposed to go out to the pin and the other contains the value of the pin (0 or 1 for 0 or 5V). I was using the former because the register changes immediately upon writing to it while the pin may take time to ramp to voltage. However, it won't be the first time there was an error in the manual. So I can try using the direct pin readback instead of the register. To avoid the problem of voltage ramp delay to the pin, I am going to write out to the port in one write statement so both bits get read and set simultaneously. Right now they are set sequentially - but with only well under microsec delay between the writes. I will send out a test version tonight.

The other thing I can do as a diagnostic is to compare the registers. When you write say a 1 to the register, it is supposed to go out to the pin. So the pin readback should very quickly match the register value. However, if there is a short on the pin, they will not match.

Joe, there was no change in the code versions that would affect anything about the IAC. The moving only mode only enables the stepper before a move and disables it after. If the always on or always on for 15 min makes things worse, it is possible you have a wiring problem that is making the stepper chip get hot. Also, all the leds will show is some flashing, but it will be way too fast to tell what is going. Of course if only one led flashes that would indicate an electrical problem.

BottleFed70 · Post by **BottleFed70** » Tue May 09, 2006 11:13 am

Thanks for the info Al, let me know when you have something you'd like me to try.

Should I still give the 2.35x2 code a try?

Post by **grippo** » Tue May 09, 2006 4:58 pm

Well I finally found the bug in the software that explains the scope traces. As shown on the scope, the first pulse is wrong and it is due to the fact that the inverse bit pattern is being sent out on the very first step. This is in the code section (move_motor) that sets up the move. Thereafter, the bit pattern is correct. It does NOT explain why this has a big effect on some people and not others. Had this been a consistent error or even a random one that affected everyone from time to time the problem would have been caught before the code was ever released. Anyway, the new code is ready to be tried and is attached. Sincere thanks to Scott for the scope traces, and to all who provided valuable data for tracking down the problem. Hopefully this will solve the problem for many of you.

Ballistic · Post by **Ballistic** » Tue May 09, 2006 5:16 pm

Thanks Al, I'll put this to use in the morning.

Joethemechanic · Post by **Joethemechanic** » Tue May 09, 2006 7:39 pm

Joe, there was no change in the code versions that would affect anything about the IAC. The moving only mode only enables the stepper before a move and disables it after. If the always on or always on for 15 min makes things worse, it is possible you have a wiring problem that is making the stepper chip get hot. Also, all the leds will show is some flashing, but it will be way too fast to tell what is going. Of course if only one led flashes that would indicate an electrical problem

Yea, quite right on that. The stepper commands do move quick! I was actually planning on setting he step size ( ms ) to a very large number to aid in seing what was going on but it seems you have got a handle on it!

As far as the moving only and always on I do know the differances, I monitored th temp of the chip too closely, I just didnt want to burn it up!

I will rey the new code, THANK YOU!!!!
Joe

BottleFed70 · Post by **BottleFed70** » Tue May 09, 2006 8:29 pm

WUHOOOOO!!!

It works! It works beautifully!!! If you guys could only see the smile on my face.

THANK-YOU AL, and everyone else who helped find the solution..this is great!!

BottleFed70 · Post by **BottleFed70** » Tue May 09, 2006 8:37 pm

So I have a question..

Is there any possibility that this programming glitch could have resulted in any other problems with the ECU?

The reason I'm asking is because I had been having a problem with my fuel only MSII suddenly "hickup" for a split second. Especially around 3000rpm. Looking at the datalogs it was hard to tell what the problem was... it sorta looked like tach spikes/dropout on the datalog, but it was hard to actually nail down and often did not show up as a tach spike but you could see a dutycycle spike (not accell enrich) the ECU didn't appear to be resetting although I did see the odd reset after a particularly bad event. Anyways, it appears as tho this new version of the firmware has fixed this problem as well? Or at least dramatically reduced the frequency?

The only changes since my last test drive has been the firmware and I'll need to take the car for a couple more test drives to know for sure, but it sure seems better.

You guys think it was just a coincidence?

krisr · Post by **krisr** » Tue May 09, 2006 8:49 pm

I'll test the code tonight, if it works I suggest Al sends us all a paypal invoice for a beer each!

BottleFed70 · Post by **BottleFed70** » Tue May 09, 2006 8:58 pm

krisr wrote:I'll test the code tonight, if it works I suggest Al sends us all a paypal invoice for a beer each!

I'd buy HIM a beer if I could

krisr · Post by **krisr** » Wed May 10, 2006 2:09 am

Ok, Al is now on the list of people to buy a beer for when I head over to the states!

She works perfect now on demand!. A good example is when I pulled over in a backstreet tonight with the car running, reset my idle step curve so that it was fully open and aswell as picking the RPMs up, dropping map I could actually hear the air whistling through the bypass, set it back to the way it was before and it would return back to an idle of 850rpm.

Since this problem has been so intermitten, it might be worth while getting someone who said they had a working IAC with the old code to test the new code?

Thanks again Al!