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Thread: Opensource LS Flashing(It's Closer Than You Think)

  1. #16
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    Can you use raw binary data instead of the AVT data interface? To be clearer, are you attempting to emulate the AVT852-E and are looking for less costly hardware, or are you willing to work with a direct serial translator instead?

    If so, I'll have a 1x/4x capable hardware unit posted here shortly. It'll be atmel based so you can run your current VPW implementation if you'd like, I'm putting the old design through the wringer right now to make sure it'll do what you need it to do. Also, you could simply use the Harris or Fairchild bus interface chips to do the hardware, they're discontinued but available through second-source vendors. I have been pulling them from GM body control modules, they're surface mount so you need to be good with a hotplate.

    Also the AVT interface is available directly from AVT, you can buy singles at 250ish dollars each. That's where mine came from.
    Last edited by Xnke; 02-24-2018 at 02:13 AM.

  2. #17
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    Xnke,

    just how soon is "shortly:? :-)

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  3. #18
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    Quote Originally Posted by Xnke View Post
    Can you use raw binary data instead of the AVT data interface? To be clearer, are you attempting to emulate the AVT852-E and are looking for less costly hardware, or are you willing to work with a direct serial translator instead?

    If so, I'll have a 1x/4x capable hardware unit posted here shortly. It'll be atmel based so you can run your current VPW implementation if you'd like, I'm putting the old design through the wringer right now to make sure it'll do what you need it to do. Also, you could simply use the Harris or Fairchild bus interface chips to do the hardware, they're discontinued but available through second-source vendors. I have been pulling them from GM body control modules, they're surface mount so you need to be good with a hotplate.

    Also the AVT interface is available directly from AVT, you can buy singles at 250ish dollars each. That's where mine came from.
    Raw binary is fine, we're designing the next app(s) so that the raw binary payloads are totally separate from the details of the different interfaces. That should make it relatively easy to support different interfaces. Antus wrote the proof-of-concept and has an AVT, so that will probably be the first interface to work, but I'm not planning to buy one just yet. As a software developer I'd prefer the "direct serial translator" approach. But as someone who wants there to be an active community of people hacking 0411 PCMs, I really just want there to be an interface that is inexpensive and readily available. $250 could work, but that price point seems to leave a lot of room for improvement. DIY SMT isn't going to work for very many people though, so I'm not real excited about that approach.

    What do you think about getting productizing your design through service like seeedstudio.com? Or PCBs through oshpark.com, a case through shapeways.com, OBD2 connector with pigtails from Amazon, etc, etc, so anybody with a soldering iron could build one?

  4. #19
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    The problem with things like oshpark and seeeedstudio is cost. You can't buy just 1 board through those guys, and oshpark is 3 boards for close to 100 bucks all told.

    You can't buy a lot of the parts and bits you need in through-hole anymore, you'd be buying breakout boards and main pcb's and pin headers...SMT is very easy to do at home, but people see it as scary so no one tries. It's actually much cheaper and faster to do than through-hole!

    gotta go, second and possibly third tornado today just sounded the warning-if I have power in a few hours I'll start posting schematics.

  5. #20
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    I will agree though hole is NOT fast, but at the same time SMT also requires a great deal of knowledge to use less then ideal tools.

  6. #21
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    Here are some useful links for anybody that wants to build a custom interface for VPW bus.

    https://forum.macchina.cc/t/support-...-vpw-pwm/67/34
    https://www.irjet.net/archives/V4/i7/IRJET-V4I791.pdf
    https://www.nxp.com/docs/en/application-note/AN1731.pdf

    Transciever is a must and all the transcievers are surfice mount type. Most are 8 pin SOIC package. Cracking an old pc motherboard will give you a good starting point for creating custom board with surfice mount components.

    If you plan to add support for CAN bus vehicles, there is an available break board with tja1050 transciever ready to be linked with arduino or other types of interface.
    Last edited by kur4o; 02-26-2018 at 04:01 AM.

  7. #22
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    None of the J1850 transceiver chips are in production or are available from distributors anymore. You can't buy them except through second-sourcing and counterfeits. They are *available* but it's hit or miss that they're real...Which is a real shame. Only reason I haven't posted the schematics and board layouts yet-I've been using the transceiver chips robbed out of old GM modules.

    Anyway, if you CAN get the transceiver chips, you want the MC33990 or MC333990 from Freescale-by far the easiest to work with AND they will both do 4X transmit mode. The Harris HIP7020 will not do 4X transmit, only does 4x receive and 1x transmit. The chinese AUP7020 is the same as the harris-1x transmit and 1x/4x receive.

    The current non-transceiver chip design is based on the BSS138 mosfet level shifter. The issue is that it no waveshaping is done in 1X mode, which means for datalogging and normal communications in 1x mode, you're dumping a lot of hash onto the bus that other transceiver chips don't want or expect and might cause problems. In 4x mode, the VPW protocol does away with waveshaping and runs without it-so the level shifter trick works fine and is actually compliant. This method, however, will not work for J1850PWM mode...which we don't care about for GM.

    For basic usage, just grab one of these:

    https://www.sparkfun.com/products/12009

    and supply the "LV" side with +5v, and connect this side to your arduino pins. Then on the "HV" side, connect a 8V, and tie the two IO lines together to go to the J1850 bus-same as you'd do for an ALDL interface.

    The BSS138 is the part I use in my non-transceiver design but since everyone is afraid of SMT soldering, the breakout board above will let you get it done "through-hole" style.

  8. #23
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    As far as wave shaping, couldn't it be done with an RC filter. All its really doing is creating a non-digital type signal correct? a little slope on either side of rising/falling edge? Or am I offbase with that train of thought? Also. whats the cutoff voltage, I know it expects ~7vdc as high with a separation state of 3.5vdc, but is 5vdc enough to get the job done, say with an "off-the-shelf" unit like the arduino? Just spitballing here so feel free to correct/educate me. Im not new to embedded controls, but I am still learning the j1850 VPW setup.

    Bud
    If it don't fit force it, if it don't force fit f&%@ it!

  9. #24
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    Yes and no. You won't get reliable data transfer with 5v logic highs-and you're going to be receiving 8V coming back at you which will destroy the arduino very quickly. You can make it work on a bench harness at 5v but not in a vehicle.

    The wave shaping requires an RLC filter, and to get to the specified VPW "exact spec" is pretty tough-we can pretty well ignore it though if we go to 4x mode, which doesn't use the waveshaping at all. It's easier (and works well enough to do the job) to ignore the waveshaping in *most* cases. You're likely to run into a stubborn case that will have some dropped frames and the like in 1x mode if you don't use the waveshaping, but for flashing and receiving datalogging info, it'll be OK for 90% of cases.

    On the receive side not only do you have to level shift, you need to use a comparator to clean up the logic signals-they are going to be pretty muddy without it and will have a lot of framing errors.

  10. #25
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    Ok, so this is the surface mount, but still 100% all parts available nothing hard to find VPW transceiver hardware. Just checked it, this works in both 1x and 4x modes and if you just use the VPW translation circuits (top part of the drawing) then you could adapt these to any Arduino or PIC or Motorola processor you wanted. As is, the drawing contains an ATmega32U4, configured as per the ArduinoMicro style board. I'm going to verify footprints and make sure the layout isn't too tight for the supercheap board houses to do properly, and I'll send the schematics and board gerbers to whomever updates the Github stuff.

    Technically the interface could be completely done in through-hole components but it'd be about the size of a postcard, but since we're working at baseband and the symbol rate is relatively low, it should still work in a through-hole board.



    If you don't care about the ATMega32U4 and associated stuff that has to be there for it to work, and you only want the J1850VPW stuff, then start at the OBD-II connector and work from there-you'll see where it translates out to just the J1850VPWRX and J8150VPWTX lines. Yes, the two voltage regulators are both LM7805's, the D2PAK versions, and to get the 7.6v to transmit on the VPW bus, we just put four diodes in series from the GND leg of the voltage regulator to ground-this lifts the regulator 2.6v over ground, and provdes a 7.6v rail to the transmit assembly.

    Since I cut a lot of unneeded junk out of this board that handled CANbus as well, I need to re-do the PCB layout. I'll get it posted up as soon as possible.

  11. #26
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    A VPW bus operates in two states: Active In the active state, the bus is driven between 6.25 V and8.00 V. Passive In the passive state, the bus is pulled down to between
    1.5 V and 0 V.


    Xnke do you have more info for 4x mode. Does the pulse width get slashed by 4 and there is no rounding of the waveform, or is something else done.

    The most simple solution for smt is to get 8 soic to dip adapter. Ebay is full of them.
    33390 and 33990 are availabe through aliexpress and are sold in 5 or 10 pieces. They look geniune also and the average price is 1$ per piece.
    I have a busted bcm from w-body that uses 33390 and will post the schematics from the bcm.

  12. #27
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    4x mode has no rounding of the waveform and as far as I can tell, the pulse width windows are just divided by 4 to push the data rate up-the rest of the spec is the same.

    I have yet to purchase a "good, working" 33390 or 33990 anywhere on the net-I've been pulling them from BCM's myself. Doesn't take much, a little hot air and some tweezers has netted me a few. I've even done it in the junkyards with a cigarette lighter and tweezers, just have to be very careful.

    I tried to make a video on how to do SMT soldering very easily at home, but my GoPro doesn't have the close-up abilities to show very clearly what's happening and how easy it really is. I'll have to get a new camera to do it.

  13. #28
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    Now I've done it...

    The boss is not gonna be happy, I have been picking at this for over 24 hours now, grabbed some fairly basic VPW code for Arduino off of Github and have been re-writing it as a state machine, integrating support for both the discrete optoisolator/transitor-comparator hardware and the MCZ33390/33990, and including 4x transfer mode.

    Only things left is to get it working in AVT compatible mode so all the ADX's that Dimented24x7 wrote will work still, and then figure out how block transfer mode should work because I got no clue how that happens.

    Oh yeah, I probably ought to plug this into a whole truck and see what happens...so far all testing has been in the lab and I haven't *broken* anything yet...

  14. #29
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    Quote Originally Posted by Xnke View Post
    Ok, so this is the surface mount, but still 100% all parts available nothing hard to find VPW transceiver hardware. Just checked it, this works in both 1x and 4x modes and if you just use the VPW translation circuits (top part of the drawing) then you could adapt these to any Arduino or PIC or Motorola processor you wanted. As is, the drawing contains an ATmega32U4, configured as per the ArduinoMicro style board. I'm going to verify footprints and make sure the layout isn't too tight for the supercheap board houses to do properly, and I'll send the schematics and board gerbers to whomever updates the Github stuff.

    Technically the interface could be completely done in through-hole components but it'd be about the size of a postcard, but since we're working at baseband and the symbol rate is relatively low, it should still work in a through-hole board.



    If you don't care about the ATMega32U4 and associated stuff that has to be there for it to work, and you only want the J1850VPW stuff, then start at the OBD-II connector and work from there-you'll see where it translates out to just the J1850VPWRX and J8150VPWTX lines. Yes, the two voltage regulators are both LM7805's, the D2PAK versions, and to get the 7.6v to transmit on the VPW bus, we just put four diodes in series from the GND leg of the voltage regulator to ground-this lifts the regulator 2.6v over ground, and provdes a 7.6v rail to the transmit assembly.

    Since I cut a lot of unneeded junk out of this board that handled CANbus as well, I need to re-do the PCB layout. I'll get it posted up as soon as possible.
    That is for more complex then it needs to be.

    https://www.mouser.com/ProductDetail...7PIwC%252bY%3d

    A VERY simple circuit is all that's needed and it can do both 1x and 4x

    Datasheet....
    http://ww1.microchip.com/downloads/e...Doc/39626e.pdf

    And best of all it's still in production and comes in a DIP package.

  15. #30
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    Quote Originally Posted by Xnke View Post
    Now I've done it...

    The boss is not gonna be happy, I have been picking at this for over 24 hours now, grabbed some fairly basic VPW code for Arduino off of Github and have been re-writing it as a state machine, integrating support for both the discrete optoisolator/transitor-comparator hardware and the MCZ33390/33990, and including 4x transfer mode.

    Only things left is to get it working in AVT compatible mode so all the ADX's that Dimented24x7 wrote will work still, and then figure out how block transfer mode should work because I got no clue how that happens.

    Oh yeah, I probably ought to plug this into a whole truck and see what happens...so far all testing has been in the lab and I haven't *broken* anything yet...

    Obdlink MX supports 3K packets

    ObdLink Sx Suports a touch under 2K packets.

    Adx files already exist for Elm protocols.

    Did this last week just messing around to see what would happen......
    https://www.youtube.com/watch?v=IMQU2gDfpOg

    I'm so tempted to write the code into my current Android app just to see big blocks.....but I'm in the middle of a total rewrite on the app changing every thing to block mode and I really don't want to add it into a outdated version. The rewrite is a long ways from being done but I'm going for stability with the rewrite not just making it work in the fastest possible time.

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