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Tapping the AVCLAN/IEBus

Discussion in 'Gen 2 Prius Audio and Electronics' started by Dngrsone, Apr 4, 2008.

  1. Dngrsone

    Dngrsone Underwhelmed, to say the least

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    I have a basic model '08 Priius and would like to retrofit an auxiliary input to my (albeit lousy) sound system.

    Ideally, this would be a simple wiring operation or the installation of an inexpensive adapter, but this doesn't seem to be the case-- there are few adapters out there outside the overly expensive (and not solidly reliable, I hear) DICE.

    So, I am thinking about installing a carputer and using that as my music storage and playback device and somehow tapping it into the AVCLAN to accomplish that.

    Everything relating to the bus in the forums here seems to be a few years old... any newish insight? How do I build or find an interface to plug into the carputer?
     
    #1 Dngrsone, Apr 4, 2008
  2. Presto

    Presto Has his homepage set to PC

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    Check out this thread. I helped my cousin out with a carputer, but we didn't bother with the AVCLAN. A simple AUX-BOX was all that was needed to get audio through the stock system.
     
    #2 Presto, Apr 6, 2008
  3. Dngrsone

    Dngrsone Underwhelmed, to say the least

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    Thanks, Presto. Some light reading for me. :)
     
    #3 Dngrsone, Apr 6, 2008
  4. Dngrsone

    Dngrsone Underwhelmed, to say the least

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    Okay, got a killer deal on a carputer:

    Epia Nano ITX N8000E with Via Corefusion 800MHz Processor
    M3-ATX Automotive Power Supply
    Fujitsu 60GB Notebook IDE HDD
    512MB SO-DIMM DDR RAM PC3200
    Lilliput EBY-701 VGA Touchscreen Monitor
    Playstation2 USB Thumb Keyboard
    4-port USB 2.0 Mini-hubxt
    UT-41 USB GPS

    All for $380, shipping included. That's like getting the Lilliput for free.

    So, I am looking at integrating the carputer into the sound system-- I need to interface with the AVCLAN, tell it that the carputer is a CD Changer, and be able to ship my audio to the sound system. I'd also like to be able to push CD text to the MFD via the head unit and control volume, etc from the steering wheel controls.

    This site has some interesting projects along that line, and here is a slightly different take on the aux-input enabler.

    I like the second one a little better, I think the design is a bit more elegant. With that said, however, we are talking a different animal here-- I need a little more interface than the aux-only device is doing, but different than an iPod interface. Additionally, I am likely going to have to hack up whatever music playing software I am going to use on the computer itself, which should prove entertaining, at the least (it's going to be a Linux, so that's one thing in my favor).

    Any insight and/or observations are welcome... this is going to be a huge projet for me, as my engineering knowledge is some two decades old.
     
    #4 Dngrsone, Apr 24, 2008
  5. Dngrsone

    Dngrsone Underwhelmed, to say the least

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    Okay, $11 netted me two NEC uPD72042BGT-A surface-mount IEBus interface chips. Looks like the NEC uPD789801 is the processor to get. It will communicate with the IEBus chip via 3-wire serial and it hosts a USB 2.0 connection for communication with the carputer.

    I also found a microprocessor that has both IEBus and USB: Renesas R5S72632P200FP, but I can't find a source of supply on it.

    Then again, I'm having a little trouble finding a SoS for the processor chip. :argh:

    The N8000E doesn't have a serial bus, but it does have an LPC connection... I wonder if I can program the PD72042 to communicate with the Epia through that...
     
    #5 Dngrsone, May 15, 2008
  6. momanz

    momanz Junior Member

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    take a look here.

    Ive been wanting to play around with this but have never had the time to do it.

    Cheers,

    -Momanz

    Opps didn't read Dngrsone's post as closely as I should have...
     
    #6 momanz, May 16, 2008
  7. electricitylikesme

    electricitylikesme New Member

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    This thread is serendipitous - I've just now finished testing my implementation of an IE Bus snooper that runs on a PIC16F628A chip (much more common and easy to get around here though I have a few Atmega things around now that I might learn to use one day).

    It connects to the IE Bus through the driver that Marcin developed for the Corolla (though technically provided you emulated the functionality one way or another it'd work with anything) and prints out the messages it receives via the USART.

    Did it chiefly because no one else had (everyone else used Atmel processors) :)

    Next up to give it transmit ability!

    EDIT: I've posted my current source code for the PIC and a description of the basic setup over at Marcin's forums -
    Toyota Corolla MP3 Player :: View topic - Is there anyone try to use PIC IC instead of ATMEL IC?
     
    #7 electricitylikesme, May 18, 2008
  8. Dngrsone

    Dngrsone Underwhelmed, to say the least

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    So you are reading the IEBus how? Through a CAN interface?

    It looks like the Renesys chips have been discontinued... All I need is an interface between my chips and the Epia motherboard. Unfortunately, it doesn't have a serial port, which would have been easiest to implement.
     
    #8 Dngrsone, May 18, 2008
  9. electricitylikesme

    electricitylikesme New Member

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    Marcin's circuit uses the CAN driver chip to send on the IE Bus. The receive is handled by the quad voltage comparator IC (I'm sure others would work but for my test project I wanted to use something that had previously worked before).

    The "AVC-In" port on the circuit supplies TTL logic levels as the IE Bus changes - it gives +5V when the bus is logical zero (voltage difference detected) and 0V when the lines are logical one. I wrote my PIC snooper around that.

    Of course I've done all this because getting the NEC chips is pretty much out of the question for me (and I'm not really set to do surface mount electronics at the moment).

    If all you need is an interface between your chips and the motherboard, you should be able to buy a DB9 header which will plug in somewhere on the EPIA motherboard to give you a serial port that will suffice.

    Also, as I understand it the interface to the uPD controller from NEC is pretty standard - you should be able to implement it on something like a PIC or Atmega chip. I suppose there might also be some way to skip the extra microcontroller and interface it directly to a PC serial port (just need a baud rate generator for the serial clock I think).
     
    #9 electricitylikesme, May 18, 2008
  10. Dngrsone

    Dngrsone Underwhelmed, to say the least

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    Yeah, I don't have an RS232 port on this one... best I can go with is an LPC interface. I know nothing about that protocol, so I have no idea if the serial interface on the uPD chip will work or if I have to use an NEC microcomputer as a go-between.
     
    #10 Dngrsone, May 19, 2008
  11. electricitylikesme

    electricitylikesme New Member

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    Well something like $35USD should net you a serial<->USB adapter if you're in a bind. I've been using one with my laptop to debug my PIC interface.
     
    #11 electricitylikesme, May 19, 2008
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