240p output on 3DO with BT9103 encoder

Discussion in 'Panasonic M2 and 3DO' started by Taijigamer2, Jul 27, 2017.

  1. Taijigamer2

    Taijigamer2 Robust Member

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    So on my adventures trying to look into the elusive hardware of the Panasonic 3DO, I decided to try and figure out the lesser known BT encoders. The later FZ-10 mainly came with the VA536 video encoder which fortunately has a well documented datasheet telling us which pins do what. Unfortunately the BT (BrookTree) encoders have no datasheets available. I have searched high and low for these elusive datasheets but no luck. The BT910x encoders have been seen in both 3DO and Philips CDi hardware.

    So without a datasheet I decided to try and use trial and elimination to work out as much of these encoders as I could. Fortunately my FZ-1 came with the BT9103 encoder. This encoder has the same package as the VP536 (68 pin QFP) and we know from Airs' thread that 2 pins are responsible for selecting between PAL/NTSE and Progressive/Interlace. I was hoping the BT encoders followed similar principals.

    So eliminating pins we could already work out (24 RGB pins, VS, HS, Y, C, CVBS) The next step would be to lift remaining pins and tie them high or low and observe the result. Obviously the chance of damaging the chip was probably quite high. Fortunately after a little searching, I came across a CDi thread which mentioned the BT856 encoder. http://mjpeg.sourceforge.net/driver-zoran/datasheets/bt856.pdf
    This encoder has the same pinout as the BT9103 encoder. As we can see, 2 pins control the region and interpolation (pins 59, 60).


    upload_2017-7-27_22-4-57.png

    I checked my board and found as expected pins 59 and 60 held high (5V) which corresponded to my region (PAL) and interlaced. When pin 59 was lifted and tied low to GND, the console was put into Progressive mode.

    IMG_2049(800).png

    I couldn't get a good picture of the result as I don't have an RGB mod or capture card but there was a definite improvement on picture with CVBS, pixel crawling stopped and the pixel edges became much more defined. S-Video, the result wasn't as profound. So if anyone has the BT9103 encoder and wants to try this mod to confirm it with RGB and capture card, please do.


    IMG_2047(800).png

    I soldered the wires to a DPDT switch with the middle wire going to the original pin 59 (BLUE). Another wire going to 5V and the final wire going to GND. I chose 5V from a nearby pad (RED) but any 5V point will do, same with GND (GREEN).


    IMG_2056(800).png

    I found unreliable behaviour with the pin still soldered to the board. The datasheet has the maximum voltage for a low input at 0.8V. When I measured the voltage with both 5V and GND tied to the pin, it measured 0.2V. This could be causing erratic behaviour so I recommend lifting the pin from the board for best results. Also, the FZ-1 had no problems booting in 240p in this configuration. Switching between 240p and 480i with the BT9103 causes no issues mid operation as the chip switches during ODD fields to prevent syncronisation disturbance.

    You could also tie the pin to GND without the switch to give permanent 240p but I have read that some games behave weirdly in 240p.

    IMG_2038(800).png

    Hopefully this mod is useful to people with the BT9103 encoder. After experimenting thoroughly with the pins, unfortunately the RGB pin seems to be redundant in these chips. This has also been confirmed for the BT9106 encoder used in some Philips CDi units as per this thread. The BT9107 may have the RGB pin active so there is a possibility to swap the chips to potentially mod the console for native RGB but I would need a BT9107 to test this. Until then, I will be also looking into dedicated RGB encoding with modern ICs.

    The next task is tackling the BT9101 encoder. This encoder has 160 pins and no similar datasheet so it will be a bigger challenge. We now know the 'style' of the BT chips so once we eliminate the known pin functions, it shouldn't take too long to work out and may even retain the RGB function.

    If anyone has any 3DO with BT9101 encoders and fancies a challenge ;)

    Special thanks to:

    Superg
    Airs
    and RetroRGB

    for their generous sharing of knowledge in the field of RGB modding of legacy consoles.
     
    Last edited: Aug 7, 2017
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  2. MeteK

    MeteK Rapidly Rising Member

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    Great !!
     
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  3. Taijigamer2

    Taijigamer2 Robust Member

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    So after a little more investigating, I came across another datasheet for a similar 160 pin DAC by BrookTree, the BT858. Data sheet here.

    Bt858.png

    The pins seem to conform to the pins of the BT9101 encoder. I don't currently have an FZ-1 with BT9101 encoder to check so if anyone with this encoder could confirm this. We can see from the datasheet that this encoder only produces 2:1 interlace video so unfortunately a 240p mod on this encoder is out of grasp unless someone designs a board with the necessary SYNC generator and CLK signal.

    Interestingly the datasheet also shows a single CVBS output which would explain the switch on the back of the earlier FZ-1 models for channel select.

    Installing an RGB board is obviously still an option, in 480i, but will be easier because CSYNC can be grabbed directly from pin 159. The other encoders don't have a dedicated CSYNC pin and require a sync stripper (LM1881) to get SYNC from Luma instead.

    Hopefully this is useful to people with BT9101 encoders.

    Next step is to finish designing an RGB board using the BU3616K to make a smaller and easier to install board.
     
    Last edited: Aug 7, 2017
  4. kimaq

    kimaq Newly Registered

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    Hi,
    I'm going to rgb mod my FZ-1 and need some info from anyone that have it done.
    Are there any step by step guides available? I've gathered some information but I'm not sure if thats all I need.
    Looking at application example from datasheet:
    Zrzut ekranu 2017-09-04 o 23.33.38.png
    Pins 7,27,32,35,39,43 are all connected to 5V
    Pins 2,6,28,34,38,42 to GND
    RGB outputs through RL(75ohm?) to GND.
    Is it right?
    What is Rref?
    Where should I get 5v and GND from?
    What about sync? Can I just route composite video to scart?

    Can I use BU3618K instead of 3616K?
     
  5. Taijigamer2

    Taijigamer2 Robust Member

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    What video encoder does your FZ-1 have?

    I've designed a pcb to use the BU3616K but I still need to test it with my 3DO. I added a LM1881 sync stripper to it to get clean sync from Luma. If u are just going to wire a video output to your sync pin, I suggest Luma rather than CVBS as its 'cleaner'.

    BU3618K should be fine to use as well, not much difference. The rRef is used to set the current output amplitude. The rRef for the 3616k was 6.8k. This was found result in a dim picture by a modder who used this chip in Japan. He reduced it to 1.9k and found it to be still a little dim but he was happy. My calculations found a rRef of 1k with Rl=100 Ohm resistors to GND to be close to the desired 75 Ohm impedence and 700mV signal amplitude for RGB. But I haven't tested these values yet.
     
  6. kimaq

    kimaq Newly Registered

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    It's Jap FZ-1 with VP536. I've already done 240p switch mod and it's working great. I must say that s-video output on this console is really good comparing to other systems. But I need to route it through dvd recorder and then OSSC, so I want to do an rgb mod.

    Are you going to share your project to the community later on?
     
    Last edited: Sep 5, 2017
  7. Taijigamer2

    Taijigamer2 Robust Member

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    I agree, the S-Video is nice for this console. Like u, I want to build an OSSC in the future which is why I'm trying to get all my consoles fitted with RGB. I found that there is very little info on the 3DO so I have been compiling as much info as I can as well as developing solutions where there are none available. The old RGB method is outdated but maximum respect to Acen77 for developing it.

    My design should work for all 3DO encoders accept the newer Anvil combined chip. I plan on making the chip publicly available along with all the info I have acquired, I just need to check the design on all encoders. If u want test the design on your VA536, give me a PM. :)
     
  8. kimaq

    kimaq Newly Registered

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    I've just ordered some BU3618/BU3616K from china seller. Couldn't find it anywhere else. I think it can take up to 1 month to arrive and I'm willing to try your design.
     
  9. Taijigamer2

    Taijigamer2 Robust Member

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    PM sent.
     
  10. Self_Control_Me

    Self_Control_Me Newly Registered

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    i have the bt9101 in mine and would like to try your design with the BU3618/BU3616K
     
  11. Taijigamer2

    Taijigamer2 Robust Member

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    That's great. Pm sent.
     
  12. Friend of Sonic

    Friend of Sonic Spirited Member

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    I'm excited to see where this goes. I was so bummed out that I couldn't get in on 240p
     
  13. Taijigamer2

    Taijigamer2 Robust Member

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