P2DIP40 (for existing P1 sockets) and P2DIL80 (for new designs) - board details tomorrow!

I've been working for some time on some DIP40-centric P2 designs quite similar to what Dave Hein was proposing with his P2 QUIP concept.

If we're doing a video conference tomorrow then I can share details then, otherwise post pics here


  • Sounds interesting :)

    BTW Forum problem has dual posts :(
  • I deleted the duplicate
  • Thanks Jim. Made a phone call in the middle and forgot I already posted it. Much appreciated
  • Here's an overhead plan view of the board when configured as P2DIL80

    In this configuration there are two 40 pin DIL headers, like used with PC104, Pi and other systems (ie common), connecting the PCB down to a host pcb underneath.

    You can think of two counterclockwise circles of I/O
    - The inner circle is P2 port A (P0..31) and matches the format of the Prop1 (P8x32A-D40)
    - The outer circle is P2 port B (P32..63), including pins to match up with 2 Mikrobus sockets. There are also SPI, Prop Plug, Cascade pins in this circle.

    There are a couple of pins marked NC, these are not used (pulled out/cut) due to where the P2 is positioned underneath the board.

  • Here's a fancy ISO drawing of P2DIL80

    I'll come back to this and make the text a bit thinner/more legible later
  • Regarding P2DIP40,

    This uses the same pcb, but in a slightly different way. There are only single rows connected down to the board below. Pins P16 through P31 mount in an adjacent row 0.1" closer, to provide the correct overall 600 mil spacing to fit the standard P1 Dip40 socket.

    I'll post an iso drawing showing this later
  • roglohrogloh Posts: 2,767
    edited 2020-10-08 - 00:43:30
    It looks pretty interesting Lachlan. I'll have to watch the YT later to hear more about it once it's posted. One thing I realized with the Mikrobus wiring on your diagrams is that it's rotationally symmetric on your board, but any newly designed custom Microbus pin compatible boards using 8 bit P2 groups like 8 HDMI pins or 8 common data bus pins for memory would need to be installed on one side only (to consistently obtain the 8 bit streamer/HDMI group in the P2 group). Either that or build two variants of the boards one for each end which is not so practical. Not going to be an issue for all the existing Mikrobus boards of course with simple SPI/I2C/ADC/GPIO interfaces. The other way to solve it is to rearrange the wiring to assign to Mikrobus pins in this order P32..P39,P40..P43 and for the other end P48-P55,P44..P47, but it will mess up your nice existing sequential order (if that matters), and might need more signal crossings on the board.
  • Looks interesting Lachlan. Missed zoom this morning so waiting for the video on youtube to check it out.
  • Yeah its a pain but I've come to embrace it this way on my Clickstart 6 breakout

    Two Mikrobus sockets have full 12 pin "untangled" wiring to P2
    - P32..43 for Hyperram, bus on P32..39
    - P44..55 for comms eg FT2232H, later we can make more compact or ESP32 S2 options etc

    Four Mikrobus sockets with 8 pin slighly muxed
    - I2C shares SPI pins like on the Mikroe dev boards (saves 2 pins)
    - INT, PWM, AN are resistively shared into a single pin (also saves 2 pins)
    - RX, TX, RST, CS and either MISO or MOSI are 1:1 mapped (not shared)

  • I'm looking forward to seeing your progress on this. When do you think you'll have working hardware?
  • We're aiming for Oct 28th, there's another presentation to give on that date
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