Cool.. I am looking to use my Nexus 7 or my Android PC I have in the car.. looking forward to this, maybe it will get me back int he groove of tuning, especially when I don't need to drag a PC with me..Originally Posted by 3400tZ
Cool.. I am looking to use my Nexus 7 or my Android PC I have in the car.. looking forward to this, maybe it will get me back int he groove of tuning, especially when I don't need to drag a PC with me..
Here are some preliminary scope images of the 86 Z28 pcm output. The first one shows the datastream's startup after the 10k resistor is connected. The next two are continuations, with some overlap so you can see how they fit together (haven't taken the time to splice them together yet). The 4th shot is a blowup of the first part of the first image. Use the "T" marker for the start position to see how it aligns with the first image. The last image is a blowup of the very narrow pulses showing in the other images, since this is a low resolution display and you can't see how wide those are in most images. The total repetition period looks to be about 1.2 seconds (very rough estimate) and is waaayyy longer that these 3 images show.
I tried to get WINALDL to read the data stream but failed; not sure why yet. Nothing appears on the screen. I have never used it before and am not sure it can read this PCM.
86-Z28 part1.png86-Z28 part2.png86-Z28 part3.png86-Z28 part1 expanded.pngnarrow pulse width.png
Ok, followup with 1st 3 spliced together:
96-Z28 parts1-3.png
Update: I got WINALDL to work by inverting the signal and selecting 4800 baud (2400/4800 available rates). Evidently the software expects the data to be input to a hardware serial port (inverted internally) or to be using an inverting cable adapter (FTDI-USB/SerialRS232 type) with a USB port. I am using an FTDI USB/SerialTTL cable and an external inverter circuit (1 2n3904 transistor and 2 resistors). Here is the WINALDL log file and screenshot that goes with the signals posted above. The PCM is an 86 CLCC (carb) F-body car.
86-Z28 WINALDL rawdata screen.png
Last edited by GaryDoug; 11-05-2013 at 07:28 PM.
Gary, thank you for all this.
To be honest, I'm not sure what to do with all those scope screenshots :D They do looks good tho :P
What do you mean by inverting the signal to get it to work in WINALDL?
I got mine to work in TunerPro no problem as well, with 4800 baud too. That's why I can't see how my hardware could be an issue. It has to be my app but I'm just reading the stream... :/
I mean that I had to put the signal from the PCM through an inverting circuit (just one transistor) to flip it over before going to the FTDI device. I don't know why that worked for WINALDL except for the reasons I mentioned above.
The scope waveforms really don't help much without some correlation showing what a working app reads for values. Attached is a marked up version of the waveforms with the bytes labeled to agree with what WINALDL sees. I believe what you were getting is actually correct, but you have to remember you are looking at just one bit for each reading. The ones that are zeros are one polarity bit and the ones that are something else are the other polarity bit. Then you would have to combine the bits of each group of 9 (one start bit and 8 data bits) to get the resulting byte. Also attached is a sample VB.net code showing what I can use to get the bytes assembled from the datastream. It is very crude but it does match what WINALDL shows. For example, when I got 0xFF, it correlated with a bit value of zero. When I got 0x00, it correlated with a bit value of one. Now that may have to do with the inversion, and perhaps if I did away with the inversion, it would be more like 0xFF=1 and 0x00=0.
96-Z28 parts1-3 invertcolors marked.jpg
p.s. I really need to change that screenshot's filename. It should be "86...." not "96...."
Last edited by GaryDoug; 11-06-2013 at 04:55 AM.
DUDE! I think that's exactly it. I need to look at byte as bit. Assemble each group of 9 (drop the first), make that a byte and put that together in a byte array. Send that over to my function that parse the data and hopefully that's it.
I'm getting FE and 00, so like you said, probably that one of them is 1 and the other 0. At that point, it's pretty easy to figure out which one is which, there is only two possible values :)
I will give that idea a try and let you know.
Really helpful, thank you! :)
FINALLY!
Progress! As soon as Gary mentioned a byte actually being a bit, everything started making sense in my head
It's slow as f**k, about 1 read / sec but I would assume that's expected for 160 baud ? I think I got the sync mechanism pretty solid already, it look for the sync byte and once it found it, it drop everything before and sync with that. Once synched, if it get out of sync again for whatever reason (ex: first bit of a byte is 1 but there is 0 after), it will go back to the same synching mechanism all over again. I had it running on the bench for half an hour and it never lost sync once so it seems pretty good.
Still some polishing to do but at least the mystery is solved!
Also, no checksum at all on those ECM ?
Gary, big thank you again to you! And to everybody else that helped at some point :D
Yep, that sounds about right for a logging rate of the 160 baud, which is why I avoid them like the plague...
The man who says something is impossible, is usually interrupted by the man doing it.
Fricken' awesome progress!
I didn't see anything about a checksum anywhere.
I got about 1.2 seconds cycle time on my PCM, which has just 20 bytes of data in the datastream.
I would like to find out why I had to invert the signal to get WINALDL to work, something unique to the app or something amiss with the setup?
In an attempt to investigate it, I could not get TunerPro RT working on my 86 PCM. I am not really very familiar with it so I would appreciate it if someone can help. The PCM I am using is from an 86 Z28 (F-body) 5.0L with carburetor. I tried the 32.xdf and the 1227165_160.adx files. I am not sure if they are the correct ones, being a newbie to this app. TunerPro RT works ok on my 94 Formula V8 PCM.
Last edited by GaryDoug; 11-06-2013 at 07:01 PM.
GaryDoug,
In regards to inverting the signal, with RS232 serial (using a UART) a "1" -12v and a "0" is +12v but with TTL serial a "1" is 5v and a "0" is 0v.
So if you're using a true USB to RS232 converter or a real serial port on a PC you need to invert the TTL signal coming from the PCM, but it you're using a TTL serial device (direct connection to a FTDI chip, no DB9 socket) inversion is not required.
This is an example of a TTL serial device: http://www.ebay.com/itm/221299939954
The description for the part above is a little vague, the trick is it only does 5v or 3.3v.
Someone correct me, but I think the 160 bps stream just sends out values from specific memory locations, I'm not sure if it calculates a checksum like 8192 does.
I am fully aware of the differences between the RS232 and TTL type devices. I have used both types and have even re-programmed them when needed instead of having to use the external inverter (not this time however). In fact, I have posted the differences in other topics before. As you may not have noticed, I stated the type I am using now (TTL) in my post yesterday. Actually, while using the TTL device, WINALDL will not work unless the signal is inverted. Perhaps that is a requirement of the app. So, in order to confirm that, I want to try the TunerPro app with the same PCM. That is why I asked for help with that one.
According to the winALDL website there is something different about the PCM's from carbureted cars as compared to injected cars: http://winaldl.joby.se/aldlcable.htm
He says in regards to building an interface cable (see link above for schematic) " R4 - With this resistor installed the interface will NOT work with fuel injected vehicles. This resisror should ONLY be used with some carbed vehicles that does not work with the standard interface. If you need this resistor then you probably have to use the 4800 baud setting in the configuration too. "
I suspect the results you are getting are specific to the PCM you are using.
Gary, I couldn't find anything in the ADX file that would tell to invert the signal so I'm just assuming the signal is always inverted for 160 baud. I agree it would be nice to get yours to work in TunerPro as well to confirm that.
Mine just worked right away with a $42 ADX file from Mark. It's in this thread: http://www.gearhead-efi.com/Fuel-Inj...Information-42
I don't see why yours shouldn't work right away as well... did you tried these ? http://www.gearhead-efi.com/Fuel-Inj...Information-6E
OK it got it all worked out.
Evidently the ECM I have, that is for the 86 carbed F-car, has an inverting lamp-driver between the ECM and the MIL. And the wire to the DLC is on the lamp side of the driver module. That apparently means it was programmed to output an inverted signal so that it would be good at the DLC. I got a hint of this from someone on the thirdgen.org web site. That means I have to supply an inverter to use the ECM by itself, instead of coming off a lamp driver output. Resolved.
As for the TunerPro connection, the ads/adx file I was using was not the correct one for the ECM, and there probably isn't one readily available. So, I used the the one that looked closest (1227165_160.ads), converted it to adx, edited it to match the ECM, and now it works fine when used with the inverter circuit. So that is resolved also.
Bottom line, my choice of an ECM was not ideal for this investigation because of the added limitation.
Did you not use a '7747?
The man who says something is impossible, is usually interrupted by the man doing it.
Posting Permissions
Reply With Quote
Bookmarks