P2 Edge

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  • Is there an
    Dave Hein wrote: »
    The type of P2 board that I would like to see would be something like a P2 Edge, but with holes for pins instead of an edge connector. It would be an 80-pin board with 4 rows of 20 pins each. There will be many applications that will not require 64 I/O pins, and could get by with only 32 I/O pins. In those cases only two of the rows would need pins soldered in them. If the two inner rows are used the board would fit in a solderless breadboard, where the wiring and some components could be put under the board. The board would also have a 4-pin connector for a Prop Plug.

    The board would look something like this. It's sort of like a Prop Mini, but for the P2.
    p2quip.png

    Hey Dave, I have a design like what you're proposing already, but its not ready for publication for a few very good reasons. I'll start a new thread so I can add to over time
  • Peter's P2D2 is pretty close to that too.
  • Yeah, inline connectors make way more sense than this edge thing, which needs a second adaptor! Great!
  • Peter JakackiPeter Jakacki Posts: 9,834
    edited 2020-10-07 - 04:36:48
    evanh wrote: »
    Peter's P2D2 is pretty close to that too.
    Yes, the new skinny P2D2 with 50mil header or smd mount is what can be manufactured in volume economically, just the one standard design. For those who want those 100mil pin headers then the thin smd module is simply mounted to the header pcb and looks exactly like the earlier p2d2 modules with dual 20x2 100mil headers. Presto, best of both worlds! The P2PAL layer can even attach to the underside of the 100mil header board so that you have all the works.
    There's also the RPi HAT and my DIP40 adapter boards that work the same way too. Mix'n'Match.

  • jmgjmg Posts: 14,541
    Dave Hein wrote: »
    The type of P2 board that I would like to see would be something like a P2 Edge, but with holes for pins instead of an edge connector. It would be an 80-pin board with 4 rows of 20 pins each. There will be many applications that will not require 64 I/O pins, and could get by with only 32 I/O pins.

    Yes, I agree, and P2D2pi is very close to that.
    It has 2 x 40 pin headers, but with the benefit of an existing widely used standard pinout.
    Why invent a new 40 pin ‘standard’ ?
  • I wonder why the P2 Edge is so large. Was this to minimize the number of layers in the PCB? Peter's P2D2 is quite a bit smaller, and he crammed a lot of stuff in it. I thought the purpose of the P2 Edge was to package the P2 such that developers could incorporate it in their own products without having to work with tightly spaced surface mount pins. It seems like the P2 Edge plus the connector will take up a lot of room on a PCB.

    Has their been any estimates on the price of the P2 Edge and the connector?
  • JonnyMacJonnyMac Posts: 7,123
    edited 2020-10-07 - 14:26:55
    The P2 Edge uses a 6-layer board so it's not that. I believe the width was based on the socket that Parallax already has (for micro:bits). The other dimension probably has to do with ease of layout. The P2D2 has been in development for a long time and has morphed into something that we didn't originally order. The Edge is a fairly new project, and is moving into production. Peter has no time-to-market pressures; Parallax does.

    Don't take this to the bank, but I think Ken said the Edge would be $49 -- same price as the original BS2. He said the connectors would be a couple dollars, and that they'll carry both styles. Yeah, it seems expensive, but one of my clients is happy about the Edge because his products are specialty, low-volume devices that he fabricates with T/H parts; the Edge and a connector allows him to move from the P1 to the P2.
  • Remember that the P2D2 started as a schematic and pcb hardware reference design since I was documenting P2 and in the process of creating a datasheet. Nobody could say what they wanted until they could see what they could get first. The P2D2 was the only P2 pcb at the time when Chip got the first P2 chips back for testing. Now the P2D2 is essentially the same layout only better and still has dual 40pin 100mil headers if you use the adapter plate. I have already ordered a lot of boards but the main production of the core module will be full P&P A&T in quantity a lot sooner than many think and by then a lot cheaper too. But somehow these threads get so crossed, sorry about that.
  • If you priced out all the individual ADC, DACs and logic / op-amp ICs - not to mention all the time and effort it would take to lay out a PCB, solder all the components in place, test the PCB... it would take at least a few days and I would still not be assured everything would work.

    Whatever the price of the EDGE it is well worth getting a project up & finished and on-line. Lots of pluses all around.
  • ...100mil headers if you use the adapter plate
    That's the rub -- I don't want to be bothered with an adapter plate, so I guess it will just sit on my desk and run code only tests. The version I thought I ordered looked like this (I used this in my P2 article).
    1024 x 768 - 450K
  • Imagine that the inner section is a thin pcb layer meshed to the pin header layer, a bit like a multi-layer board. There's a 1mm thick central core section directly mounted to the 1mm thick pin header "plate" or layer. What's the difference? It will still look the same and plug in the same way and if I took a photo of it from the same angle you probably would think it's the same pcb.
  • jmgjmg Posts: 14,541
    Dave Hein wrote: »
    I wonder why the P2 Edge is so large.

    ?
    A bare P2 edge is not large - you may be thinking of the breadboard area ?
    A connected P2 edge is a bit larger, as that includes the connector footprint.

    P2 edge looks to use via-in-SMD so it pushes the rules and layers up, but the area is kept small.
  • Dave HeinDave Hein Posts: 6,212
    edited 2020-10-07 - 20:05:30
    Large is a relative term. The P2 Edge is 37mm x 52mm. The P2D2 is 28mm x 55 mm with much more stuff on it, and the P2 is positioned diagonally on the PCB. My "large" comment refers to the 37mm versus 28mm. With less components than the P2D2, and with the P2 aligned with the PCB I would expect it to be less than 28mm.

    EDIT: The edge connector does add a few milli-meters, maybe about 5 or 6, but the P2D2 also uses a few milli-meters for pins. So maybe it's 31mm versus 25mm. I guess I should have said "I wonder why the P2 Edge is bigger than P2D2."
  • jmgjmg Posts: 14,541
    Dave Hein wrote: »
    I guess I should have said "I wonder why the P2 Edge is bigger than P2D2."
    Ah, ok, there is not much in that.
    Latest P2D2 has no 0.1” breakouts in that 28mm and fans out to two 0.05” edges, so can route tighter than Edge.
    As another compare point P2D2Pi is 38 x 58mm, which includes 2 x 40 pin headers, and 2 x USB connectors. (That also has more than Edge, or P2D2, as it has more (sub ppm) oscillator choices and has QSOP24 UB3 + ESD)

    Edge has to bring all routing to one side, so that will cost some area.
    Finished Edge size should include the connector footprint too ?
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