Anyone worked with the 16196397 yet?

[Xnke]

Do the existing O2 sensor lines have that low pass filter circuit?

I just checked my A28, it doesn't appear to have a cap in place either. Only need one of these to be suitable, I know an Innovate LC1/LC2 can source enough to drive most A/D inputs, just have to work out what the logged values would be. In this case, A28 will likely need that 1K pullup removed and reconfigured for a 10k/10k voltage divider, good medium impedance input but still a 1:1 ratio-simple 0-255 range over which to work a 0-5V logged voltage. Wideband O2 fueling control isn't really needed if it's being logged.

You seem to have A28 listed as connected to E-side 68HC11 channel 4, as well as T-side mux channel 5. Is that correct?

[RobertISaar]

i would be surprised if it were setup any differently than how it is on every other GM ECM:



since O2LO is tied to ground, the cap running from O2HI to O2LO after a 100 ohm resistor is a RC low-pass circuit. without knowing the value of the cap, hard to say what it allows though.

A28 should be a pulldown, not a pullup? it's possible I stuck my probe onto a 5V reference pad and saw no resistance, but I'm fairly certain I just used the gigantic ground planes to be certain. as-is, a 1K pulldown with a 0-5V signal will draw up to 5mA, I would think that would already be well within the wideband controller's capabilities? a 10K would obviously bring it down to .5mA peak.

with the pulldown being where it is in relation to the isolation resistor, it isn't going to form a voltage divider, if that's what you're thinking.

I do remember A28 being a weird setup.... as if the factory intended to use it for something but dropped it for production vehicles. the code never references using that channel on either PROM, so what exactly was going to be done with it, I don't know. considering that there was barely enough space left on the T-side to perform an A/D conversion, I get the feeling that there was either a 64KB PROM on at least the T-side at one point(I never check to see if the PROM's pin 3 trace was broken out or not), or it was being used as an engineering-specific extra a/d channel... no idea what they would have used it for though.

something I'm remembering at the moment is that for GM MAP sensors, there is supposed to be a 50 or 51K pulldown for the A/D channel, though I couldn't say why(a guess would be due to the MAP sensor itself being fairly high impedance), it's just something I'm remembering seeing on the datasheet for one of them. something to keep in mind should a baro sensor route be taken.

[Xnke]

It's funny you mention the PROM size, as both my 4347 and 6397 have 256K chips fitted to the board. What's limiting the program size?

Yes, the widebands I am familiar with will drive a 5mA load, but I generally try not to ask much of the sensors I can't control-with so many wideband controllers out there, some of them may not drive a 5mA sink.

I'll do a little more digging around on the board before I close up the 6397 case, make sure things are working the way I'd need them to and confirm with you that A28 is a viable input for a wideband logging input.

EDIT: It looks like on the 6397, at least in a main-power-off state, that a 0-5V input results in a 0.9 to 1.5v change on pin AD4 on the E-side MCU. That's good enough for me, I believe that logging and reporting the voltage on that pin could be used to monitor AFR. Is there enough room left in the program to log 0 to 255ADC count as a linear 10.0 to 20.0 AFR? That would work out as a simple 0-5V wideband input, usable by most brands of WB02 controller out there.

[RobertISaar]

address pin 15 could be brought over to the PROM pretty easily, but then 2 other obstacles are left: flashing program would need changed to account for a 64KB PROM on at least the T-side and then would need to make sure that the aux chips that the T-side accesses over the parallel address/data bus wouldn't be effectively disabled with the new PROM's addressing space. logic gates/address decoders would probably be ideal here, I can't remember how much control the 6811 has over its CS circuits.... probably not enough to do it through code alone.

that's really about it.

[RobertISaar]

EDIT: It looks like on the 6397, at least in a main-power-off state, that a 0-5V input results in a 0.9 to 1.5v change on pin AD4 on the E-side MCU.

you might need to elaborate a bit here... are you saying minimum voltage achieved was .9 and maximum was 1.5?



also, did some simulating of the MAP sensor, I see why the ECM uses a 51K pulldown for them now... other values cause the sensor linearity to suffer. with a 1K pulldown, it was rather interesting charting out pot position vs what the a/d converter saw.

[RobertISaar]

playing with the sim, assuming a 3-terminal sensor(essentially a pot), if the pulldown resistance actually has a HUGE effect on the signal the a/d converter sees. using a 5K pot with 5 volt reference with a 5K pulldown, center voltage is 2.0.

with a 10K pulldown, 2.22 volts.
20K pulldown: 2.35
50K: 2.44
100K: 2.47
200K: 2.48
300K: 2.49

to get back to 2.50 volts(rounding to the 1/100ths digit): you need to use a 624K(or greater) pulldown.

considering the a/d converter has a resolution of ~.02 volts, that 200K pulldown is pretty safe. response at the a/d converter is extremely linear everywhere through the range as well.

now, this was with a sensor that has 5K of impedance end to end. with a 1K pot, the same trend of needing a pulldown with 40 times the impedance of the sensor itself to keep with .02 volts of accurate through the full range seems to work here as well.

[RobertISaar]

alright, got a VERY clean looking 6397 coming in from California for $13.97/shipped. they even included a picture of the p/n sticker, has a BPJH calibration though I don't have a cross-reference for what that could be(and the lower/tearaway half of the sticker is gone), have to pull communicate with it over ALDL and check the part number that way.

[Xnke]

I know that BKRK is the 3100 Beretta Manual Trans, and BNFM is 3.4L Camaro Automatic, but BPJH I am not sure of. Possibly 3.4L Camaro Manual.

Yes, that's what I meant about the 0.9 to 1.5v range-I was using an adjustable bench supply, but the ECU was NOT powered up.

Looking at the result you had with the simulation, I am rethinking just closing up the case. Looks like I'll have to hunt down that 1K resistor and remove it, then fit a 200K or 470K resistor (I am pretty sure I have some SMT 470K's laying around...somewhere...)

[Xnke]

Ohhh, the things that this computer can do provided that a bigger PROM space is workable...

Digging through things, I *think* I see all the hardware needed to drive a Bosch LSU4.2 wideband O2 sensor, although it would make better sense to just interface a Bosch CJ125 Wideband Controller chip and run the new super-cool LSU4.9 sensor.