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Thread: 25 pin keyboard?

  1. #11

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    The 40 pin IC appears to be a 6402 UART so its serial

  2. #12

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    But what is the driver chip. The signals look like they might be rs485 or rs422 instead of rs232.
    Dwight

  3. #13

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    If it helps, here are some closer shots of those chips on the small board.

    keyboard rear circuit board .jpgkeyboard closeup.jpg

  4. #14
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    talk about bad timing. they just bought it on ebay
    https://www.ebay.com/itm/AVL-K69-Key...s/383421528752

    note the same keypad key is missing

  5. #15
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    Quote Originally Posted by SMichelsen View Post
    If it helps, here are some closer shots of those chips on the small board.

    keyboard rear circuit board .jpgkeyboard closeup.jpg
    1488/89 on the left are RS232 transmitter/receivers

  6. #16
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    I don't see any LEDs or other indicators on the keyboard, so why is the serial communication 2-way? (1488-1489)

    So the power feed must be +12, -12 (note the 7805 regulator, so +5 isn't needed).

    You have RX, TX, Gnd, that makes 5 wires, but there are 9 on the connector. What do the other 4 wires do?

  7. #17

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    It's time to sing "it's a small world", or something. That ebay keyboard is the SAME one you've all been looking at. In fact the new owner of the keyboard, who also has a CPU, just now offered it all to me! I am now officially up to my neck in AVL Eagle bits.

  8. #18

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    I suspect there may be a clock wire and possibly a data ready wire and a reset. I see lines going directly to the 40 pin chip. Is there a data circuit we can look at for this chip or is it one of those generic AY???? USART parts ( always forget the number).
    Dwight

  9. #19
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    I think it's this one

  10. #20

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    I did some careful offsets and it looks like the traces from the left go between the pins of the 6402. If they went to the pins, some would need to go to the read data.
    It would be much better to look at the board and ohm some of the signals out.
    Dwight

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