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  #166  
Old 08-21-2007, 05:01 AM
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Quote:
Originally Posted by b3lha
That is bad news. As the binary bits are coming down the wire, the converter is seeing a 1 (2 volts to 5 volts) when it should be seeing a 0 (0 volts to 0.8 volts).

I wonder if the signal voltage from the ECU is too high?
Or is your input impedance/loading too low i.e. too sensitive. A higher relative loading would pull down the output/input signal voltage. This could be where the Subaru OEM monitor differs. The fact that you indicate that a zero voltage is not being recorded, points in this direction.

The lower the monitor input impedance/resistance; the greater the signal current; lower the voltage (Dependent on output capacity) and greater the immunity to noise. In all respects the transmitted signal is more robust, a worthwhile feature.

In other words, the existing signal could be overloading your gear. Think of the affect of overloading the input of an audio amp.
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  #167  
Old 08-21-2007, 05:06 AM
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Quote:
Originally Posted by SVXdc
I'll second Jim's comments.

It would probably be smarter to keep the TTL level signals as short as possible as close as possible to the ECU. In other words, the MAX232 chip circuit should be right at the ECU plug.

Even if you leave your adapter box as-is, shielded TTL and RS-232 cables may help (if they're not already).

You may be getting additional noise if your laptop is connected to a different power and ground than the ECU (are you using the cigarette lighter jack, perhaps?).
It may be worth trying to clean up the power for the MAX232 chip. Perhaps driving it from a separate battery rather than from the car's battery.
Quote:
Originally Posted by SVXdc
So that USB-to-TTL adaptor (where the chip is inside the USB plug and the long wire is TTL) may not be such a good idea. However, one of the companies has this version that is a USB socket on a little PC board with the tiny chip right underneath it...
(img)
That could be attached to the ECU plug, with a USB A-to-B cable to connect to the laptop.
That's a cool little device. Looks like it could be installed in the dashboard somewhere. I had no idea all these things existed.
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  #168  
Old 08-21-2007, 05:15 AM
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Quote:
Originally Posted by Trevor
Or is your input impedance/loading too low i.e. too sensitive. A higher relative loading would pull down the output/input signal voltage. This could be where the Subaru OEM monitor differs. The fact that you indicate that a zero voltage is not being recorded, points in this direction.

The lower the monitor input impedance/resistance; the greater the signal current; lower the voltage (Dependent on output capacity) and greater the immunity to noise. In all respects the transmitted signal is more robust, a worthwhile feature.

In other words, the existing signal could be overloading your gear. Think of the affect of overloading the input of an audio amp.
I think I understand what you are saying Trevor. How would you go about modifying the circuit to improve matters?
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Last edited by b3lha; 08-21-2007 at 05:13 PM.
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  #169  
Old 08-21-2007, 05:29 AM
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Quote:
Originally Posted by b3lha
I assume the select monitor is a TTL device like the ECU, so no TTL to RS232 conversion is being done. This, coupled with the revelation that the Select Monitor gets good data seems to indicate that the problem is in the adapter box.
We won't know for a little while, but as I said, it seemed to have multiple "adapter" cables between the actual box and the car. Now I didn't take any photos (no camera) and I didn't use it myself... but from what I saw, it looked like the Select Monitor had a PARALLEL port (25-pin) on it, which then went into a weird lookin' thing that sent it into a port I've never seen, which he then put a cable onto that switched it from the weird port to the select monitor port used on the SVX/Legacy/etc.

I have no idea, honestly... no idea...
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  #170  
Old 08-21-2007, 06:24 AM
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Phil I need more time to look at them closely but they look to be in good workjing order... I just don't have the time to reference them right now

Tom
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  #171  
Old 08-21-2007, 07:20 AM
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So I'm watching this series about a guy asking about problems on a message board and I say to myself, why not this stuff yourself, silly?

Here's the "weird cable" that the guy plugged in. This confirms that the device used was a "Select Monitor II," PN22771AA030.



And here's the one that plugged into it. I told you it looked like a parallel port!!



Sadly I'm getting these from the dealer equivalent of Subaruparts.com, so they aren't exactly forthcoming with the technical details. I was lucky they had photos, let alone a color one. I have exhausted my Google skills without luck for finding any tech specs of the SSMII. All I can offer are these pictures, for now...

EDIT: Thinking alone garners many things. Like this.

So I'm looking at the picture of the "weird cable" that I'd never seen before, and going, "I think I've seen that before." It's the OBDII connector from the VWRX site. So then I remember that the site says that the OBDI and OBDII connectors have the same properties, just different pin locations. Makes sense that all they need is a simple cable to change forms. And then it further hits me. The cable is parallel. Vikash used parallel. And using parallel, Vikash didn't need a converter box at all... he just wired a parallel cable straight up to the Metra adapter and went from there. Is Parallel TTL? Or...something? Never mind, just d that and sure enough parallel is TTL. That answers that.

So considering the Hex Comm software is incredibly basic and the ECU accepts our commands, it's unlikely that it's the software at fault for the ECU errors. And since the SSMII works fine, then it's unlikely it's the ECU causing the ECU errors (as weird as that sounds). Which leaves only the converter box. Something is wrong with the converter box.

Phil, do you have a parallel port on that laptop you're testing with? Any chance you could mock up a really temporary test parallel cable?

Last edited by Nomake Wan; 08-21-2007 at 07:50 AM.
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  #172  
Old 08-21-2007, 08:33 AM
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I've got to say that this is a great discussion. I'll be really glad when we get it all sorted out for the '92s and can all have a reliable way of reading these ECU's. At this point the only possible assistance I might be able to offer is that I recently bought a SSM ver1 and I might be able to open it up and check out what it's using for interface circuitry. I'm not sure how helpful that will be but thought I'd offer.

Incidentally, if anyone knows the part number for the OBD1 SVX cartridge that goes in the SSM v1 I'd be happy to have that info.

Thanks, and good luck moving forward.

Jay
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  #173  
Old 08-21-2007, 10:04 AM
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Sadly, from the search I did, it would appear that if anyone knows the part numbers for the SSM1, they aren't sharing. Probably because it was superceded by the SSMII and therefore nothing for it is available anymore even if you did have the part numbers.

That said, I still don't think it's in the software. I don't think there's some special "1992 Interpretation Protocol" written in the SVX cartridge. I think it's all down to the actual connection hardware.

Which means I have to take back what I was saying earlier, sorta... maybe it is the cable... or yeah it probably is...
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  #174  
Old 08-21-2007, 12:39 PM
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Quote:
Originally Posted by Nomake Wan
Sadly, from the search I did, it would appear that if anyone knows the part numbers for the SSM1, they aren't sharing. Probably because it was superceded by the SSMII and therefore nothing for it is available anymore even if you did have the part numbers.

That said, I still don't think it's in the software. I don't think there's some special "1992 Interpretation Protocol" written in the SVX cartridge. I think it's all down to the actual connection hardware.

Which means I have to take back what I was saying earlier, sorta... maybe it is the cable... or yeah it probably is...
There is nothing special about the 92 ecu besides the fact that it doesn't read EGR temps like other years. The fact that our memory chips are interchangable between 92-95 also tells us there is nothing special... There has got to be something with the wiring like you have mentioned... Contact svxfiles about info on the SSMver1 as he owns at least 2 and knows a lot about them by now. I am looking for something that can data log the OBDI ecu for tuning purposes and sharing with my developer (LAN) on more than a verbal level. Exchanging readings to the T without having to hold the select monitor in one hand, shift with the other and steer with a phantom 3rd limb and use my 3rd eye for catching whats going on in the road in front of me... I think the SSMver1 clip connected to the SSMv2 harness is going to be your winner

Tom
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  #175  
Old 08-21-2007, 01:23 PM
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The only thing wrong with the maps you are showing is the fuel map. It seems at low load, the engine management would want to keep consistant fuel related to higher rpms... To reword that, the map should be flat in low load as rpms increase... Thats what I have seen thus far... make reference to this post ECU Tune's measurements

Tom
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  #176  
Old 08-21-2007, 02:56 PM
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Hello from Nissan land

Hi,

Just by random luck and insomnia I wandered across this thread. I don't own an SVX or even a Subaru, but do happen to do quite a bit of work with early 90s Nissan ECUs (I make a product called the 'Realtime' daughterboard, it does memory emulation that allows seamless changes to the rom while the car is running, and also bundles the Nissan CONSULT -somewhat like the Subaru diagnostic stuff- over a single USB connection, fun stuff). Anywho, it looks like the ecus have quite a few similarities on the hardware level (they're based on 77xx mcus too), and I thought this might help you guys out. If this is just duplicate stuff you already know, nevermind me.

First off, the 7791 looks pretty much identical to the 7790. I'm judging that by the matching interrupt vector tables. I bet they're pretty much the same processor, maybe a different package? If you look in this directory:

http://www.calumsult.com/calumsu/disassembler/

Under docs I've posted the short datasheet for the 7790. Also posted is a longer datasheet for a 7700 that is useful for reference. The newer 77xx chips had different peripherals (the ADC changed, etc) than the older ones, and the 7700 is in the same era as the 7790 so its peripheral documentation is useful. It has a different combination of peripherals than the 7790 though (no biggie). Combine its datasheet with the short 7790 datasheet and you've got a pretty decent 7790 datasheet.

Also listed is the software manual, but without the stupid 'EOL' splashed in the middle of every page.

Anywho, how we've got a different disassemble put together than what your using. Rather than just starting blindly at 8000, ours walks Kaele's dasm77 through the bin, using the interrupt vector table as the starting points. As it disassembles it keeps track of the M and X flag, and sets them correctly. This is a bit more complicated than it sounds, because its doing this for every single branch, and they tend to get quite nested. It takes the disassembler a while to fully run, but the end result is I think a bit more readable. I went ahead and put together a version for the SVX bin that b3lha had posted, check out the SVX directory. The disassembler will also autocomment known memory variables, and you can add to the list in a file called memory.txt. I put the locations b3lha had listed in when I ran the disassembler. The big txt file in the SVX folder is the result.

I went ahead and posted the SVX version of the disassembler exe and source code (its in C++, and compiles under the free MS Visual C++ 2005 Express compiler). Its a console app, and you need to have it in the same directory as DASM77. Also, I didn't compile it for use on machines that don't have C++ Express installed (I'll do that later), sorry!

If you want to add to your current disassembler the code above has the memory locations for the peripherals, and correct order and contents of the interrupt vector table.

Btw, on your interface problem, I'd guess that the ecu RX signal isn't exactly CMOS compatible (i.e. truly 0-5V logic). The Nissan CONSULT had a similar issue. A quick look with a 'scope would verify this (want to ship me an ecu and wiring harness, lol?). Just stick a comparator in front of the max232. I'd be happy to whip out a schematic if you need help. Also, if your wanting to use that for real datalogging I'd look into speeding up the transmission speed, the Subaru speed is just slow. Nissan has CONSULT set to 9600 baud and thats just barely fast enough for datalogging. Changing the UART speed on the 77xx is a bit of a pain in the butt, its a bit more than just changing the code, stupid old processor.

Last edited by Calum; 08-21-2007 at 02:59 PM.
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  #177  
Old 08-21-2007, 05:07 PM
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Quote:
Originally Posted by b3lha
I think understand what you are saying Trevor. How would you go about modifying the circuit to improve matters?
As you have no data to make calculations, trial and error will be the order of the day, as will be a rather crude approach to the problem.

The simple approach is to add a resistor across the monitor input as a shunt. Measure the resistance at present existing across the input and as first trial, connect a resistor of say four times this value in parallel. You will appreciate that reducing the value of this resistor, will further reduce sensitivity and increase the demand for current.

I would anticipate that a small carbon resistor should suffice in respect wattage. There will be problems of a mechanical nature in arranging connections and you will probably have to make up an in and out plug socket arrangement.
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  #178  
Old 08-21-2007, 05:36 PM
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After talking with my dad I feel a little silly... he was an expert in serial and parallel communications... so the only reason Vikash was using a parallel port was because of the voltage... he's actually re-creating a driver for it so that he can use the strobe and select ports for data instead of the actual data ports, so in fact the ECU is using a serial protocol... just some weird IEEE spinoff. Is what my dad's saying. Man I wish he were here (with a scope).

But in that case, I'm going to have to go with Tom on this one. Vikash is using a really weird way of doing things, so it makes me wonder how the official monitor does it even more. strange and svxfiles could help out a lot in this part, and I know they probably already are.

Calum, I don't know how you got here at all. Google or something? But you really did come at a great time. Thank you for all you've provided us thusfar. I'm curious; would increasing the baud rate require soldering? Is that what you mean by "a bit more than changing code?" While connecting unknown wires and crushing beads in our ECUs is...easy enough... well I know I'm not confident enough to do serious hardware modding like that. I don't have a spare ECU sitting around in case I mess it up...

This thread is awesome. Aw darn, look at the time, gotta go to work.
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  #179  
Old 08-21-2007, 05:47 PM
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Quote:
Originally Posted by Nomake Wan
So I'm watching this series about a guy asking about problems on a message board and I say to myself, why not this stuff yourself, silly?

Here's the "weird cable" that the guy plugged in. This confirms that the device used was a "Select Monitor II," PN22771AA030.



And here's the one that plugged into it. I told you it looked like a parallel port!!

You may be right, but it's a big assumption that anything with a 25pin D is parallel. Particularly on proprietrary devices like this. Remember that serial used 25pin D in the days when this car was built, before the 9pin D became common.
Quote:
Originally Posted by Nomake Wan
Sadly I'm getting these from the dealer equivalent of Subaruparts.com, so they aren't exactly forthcoming with the technical details. I was lucky they had photos, let alone a color one. I have exhausted my Google skills without luck for finding any tech specs of the SSMII. All I can offer are these pictures, for now...

EDIT: Thinking alone garners many things. Like this.

So I'm looking at the picture of the "weird cable" that I'd never seen before, and going, "I think I've seen that before." It's the OBDII connector from the VWRX site. So then I remember that the site says that the OBDI and OBDII connectors have the same properties, just different pin locations. Makes sense that all they need is a simple cable to change forms. And then it further hits me. The cable is parallel. Vikash used parallel. And using parallel, Vikash didn't need a converter box at all... he just wired a parallel cable straight up to the Metra adapter and went from there. Is Parallel TTL? Or...something? Never mind, just d that and sure enough parallel is TTL. That answers that.
Absolutely right on all counts.
Quote:
Originally Posted by Nomake Wan
So considering the Hex Comm software is incredibly basic and the ECU accepts our commands, it's unlikely that it's the software at fault for the ECU errors. And since the SSMII works fine, then it's unlikely it's the ECU causing the ECU errors (as weird as that sounds). Which leaves only the converter box. Something is wrong with the converter box.
Yes. There seems to be a problem with the converter box. But it's almost right because it works on some ECUs and all TCUs.
Quote:
Originally Posted by Nomake Wan
Phil, do you have a parallel port on that laptop you're testing with? Any chance you could mock up a really temporary test parallel cable?
Making a cable is the easy part. The difficulty is writing software to send serial data over the parallel port. The timing is critical and that is why Vikash had to write it in assembly and run it in MSDOS. I could modify Vikash's software with the SVX locations, we could use his parallel port circuit and it would probably work. But I think the serial solution is much a better bet in the long run - provided we manage to solve this annoying problem. I think we are getting close in the last couple of pages of brainstorming.
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  #180  
Old 08-21-2007, 05:55 PM
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Quote:
Originally Posted by strange179
I've got to say that this is a great discussion. I'll be really glad when we get it all sorted out for the '92s and can all have a reliable way of reading these ECU's. At this point the only possible assistance I might be able to offer is that I recently bought a SSM ver1 and I might be able to open it up and check out what it's using for interface circuitry. I'm not sure how helpful that will be but thought I'd offer.

Incidentally, if anyone knows the part number for the OBD1 SVX cartridge that goes in the SSM v1 I'd be happy to have that info.

Thanks, and good luck moving forward.

Jay
Thanks for the offer of help. One of the things I would like to try at some point is for somebody to use an adapter box in reverse. ie. Connect a PC to the select monitor instead of the ECU. Then record the commands that the SSM sends to the ECU to see what memory locations it queries in each mode.

I've seen that part number in the service manual somewhere. I'll have a look for it.

It's great the way people are taking an interest in this thread. The other day somebody emailed me a 7700 simulator/debugger. I can load the ECU dump into it, run the code and watch how it works. It makes following the code so much easier.
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