P2D2 - An open hardware reference design for the P2 CPU

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  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-04 - 04:50:29
    RTC BATTERY
    I've located a 3.4mah rechargeable Lithium battery the same 6.8mm diameter as the large supercap option. This means if you use this battery then this can keep the rtc running up to a year off power. The P2PAL or the flipside of the P2D2 allows for this footprint so there is no need to even worry about a connector for an external battery. Remember, the RV3028 only draws 40nA @3V in standby. I checked the battery app guide and I only have to trickle charge it through a resistor and diode which the RV3028 provides suitable programmable values for.

    P2D2 DOCUMENT
    I'm updating the P2D2 on-line document with brief descriptions of the accessories which I will fill in with more details later. I have trouble tracking down an smd friendly male HDMI connector but maybe I will just get hold of a passive USB-C to HDMI cable and make sure that it works. This cable can plug directly into the P2PAL and then into the monitor.
  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-04 - 05:30:08
    We all like looking at family photos? Don't we?
    Sure you do. Here are a couple of shots of a slim P2D2 family and friends with Grandpa Pee1 and cousin EsDee superimposed.

    Stop hogging the shots you lot!
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  • Nice pics Peter. Really shows off the tiny P2D2 size :sunglasses:
  • roglohrogloh Posts: 2,678
    edited 2020-09-04 - 06:13:13
    RTC BATTERY
    I've located a 3.4mah rechargeable Lithium battery the same 6.8mm diameter as the large supercap option. This means if you use this battery then this can keep the rtc running up to a year off power. The P2PAL or the flipside of the P2D2 allows for this footprint so there is no need to even worry about a connector for an external battery. Remember, the RV3028 only draws 40nA @3V in standby. I checked the battery app guide and I only have to trickle charge it through a resistor and diode which the RV3028 provides suitable programmable values for.

    :grin: :sunglasses: That's a really useful find Peter. For some products which might get powered up infrequently (e.g only a small handful of times a year) and don't have network access to set their clocks from internet etc, a true battery option like this will be handy to avoid needing to manually set the RTC each time they power up if it is used. The fact that it is rechargeable from the RTC is good too. Maybe a supercap can still be fitted in parallel with this too to speed up recharging....?

    For people who do need replaceable external batteries one thing you could possibly still do on your P2D2 is to shuffle a nearby existing ground via hole slightly and enlarge it to accommodate a DIY/BYO through hole JST-PH 2mm connector option for improved mechanical strength vs single sided SMD only attachment (which is probably possible already today without a PCB change given the leg spacing for your supercap option is very close to 2mm). See the diagram for what I mean. The matching P2PAL board hole would of course have to be drilled to line up too.

    jst2mm.png

    There are lots of these external RTC batteries and even if their polarities were to be different, the JST connector could be flipped around in a different orientation to match it. Both RA and straight connectors are possible to flip if needed. eg. something like this could be used with your board too:

    https://ameridroid.com/products/rtc-battery-for-pine
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  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-04 - 06:22:18
    @rogloh - having a rechargeable 1 year Lithium battery, why would we ever need an external battery? Being rechargeable it should never need replacing but even if it eventually did, it's only a simple two terminal coin cell. The small supercap would still be loaded as standard on the component side.

    It's just with connectors that A or B polarity becomes an issue as does the mechanical aspect on such a tiny pcb. If the P2D2 didn't bother with an integrated RTC than none of this would be an issue. So the option is always there just to use an ots module and battery such as the fake DS3231s that are use on the RPi.
  • Yes you are probably right, and I just read the soldered battery had a 100 charge cycle life worst case. That should still always outlast the life of the product so any replacement should not really become an issue. Only consideration would be long term leaks etc like you see on old motherboards, but one would expect Seiko should make quality products to last.
  • It's always surprising: Thinks take years but happen in a week! Never give up. Will happen latest in November...
  • i am hot on standby to buy this board :)
  • MJBMJB Posts: 1,192
    @Peter Jakacki
    you will put a socket for an IoT5500 on the P2D2LAB board?
    then the old EASYNET would work on P2

    just discovered this - unbelievable price $4 incl. shipping to Europe - but your IoT5500 is nicer ...

    https://aliexpress.com/item/32314544644.html?spm=a2g0o.productlist.0.0.a955430bCghLZe&algo_pvid=527416d2-7acd-44a4-b030-1d6181943e8f&algo_expid=527416d2-7acd-44a4-b030-1d6181943e8f-49&btsid=0b8b034a15994005887361179ed926&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
    HTB1jXyYcqmgSKJjSsplq6yICpXay.jpg
  • I see the exact same magjack from Aliexpress for $2.50 and the exact same module for every price between $3.40 and over $20. I do not know how they do it. Even from LCSC the W5500 chip price is already $3.30. Probably a clone although the branding minus the logo looks correct. If they work, they work, although I hate the way they continue to use pin headers to make modules standoff so high when it is so easy to use the long female headers instead and mount it inverted and flush to the PCB.

    Yes, the footprint is included in the P2LAB.
  • jmgjmg Posts: 14,480
    Here are the 3D gerber shots of the top and flipside where the P2PAL option goes.

    Compact, but looks like there is ample room there, to bump to the 24 pin UB3, which offers users more firmware features ?

  • jmg wrote: »
    Here are the 3D gerber shots of the top and flipside where the P2PAL option goes.

    Compact, but looks like there is ample room there, to bump to the 24 pin UB3, which offers users more firmware features ?

    The size is not an issue but a QFN might not be as easy to route. The main issue though is that the Si5351 is already an extra cost and the QFN is over double that. At 200 off I can get the TSSOP for 82 cents, but the QFN still costs around $2.20. If I had the room I would allow for both, but that part is packed in tight against the P2 and other clock options. I intend to use the more precise 26MHz crystals in this production run so that is already another plus. I've gotta gotta get not just the P2D2 made up, but also the P2PAL and the P2LAB, and other boards as well.

    If all is well with the P2D2 and P2PAL I may consider eventually meshing these two boards into a standard 4-layer P2D2 design. Then I can consider QFN as well.
  • Please wrap it up before I have to go to a elderly care home. I have many packets with postage on them that I may have to add another stamp to ready to go out :)
  • jmgjmg Posts: 14,480
    jmg wrote: »
    Here are the 3D gerber shots of the top and flipside where the P2PAL option goes.

    Compact, but looks like there is ample room there, to bump to the 24 pin UB3, which offers users more firmware features ?

    The size is not an issue but a QFN might not be as easy to route. The main issue though is that the Si5351 is already an extra cost and the QFN is over double that. At 200 off I can get the TSSOP for 82 cents, but the QFN still costs around $2.20. If I had the room I would allow for both, but that part is packed in tight against the P2 and other clock options. I intend to use the more precise 26MHz crystals in this production run so that is already another plus. I've gotta gotta get not just the P2D2 made up, but also the P2PAL and the P2LAB, and other boards as well.

    If all is well with the P2D2 and P2PAL I may consider eventually meshing these two boards into a standard 4-layer P2D2 design. Then I can consider QFN as well.

    I think you misread what I wrote ?
    I was not talking about the Si5351, but instead about the change of EFM8UB3-QFN20 to EFM8UB3-QFN24 .
    As well as giving access to more firmware features, the QFN24 is easier to solder and inspect than the QFN20, which has unusual corner pads.
  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-07 - 01:20:59
    Oh yes, you did say UB3, but you know that there isn't much stock of those parts don't you? I've just checked again and even octopart reports that the most I can get are 162 from Mouser although a quote only supplier has over 500. After making up a few of these new boards I may be biting the bullet and having a few hundred of these made up by an A&T shop. It's the only way I can get the BOM price per unit down and have plenty of stock with a quick turn-around.

    I do agree that the corner pads have been giving me grief but I am hopeful that the new footprints and layouts will overcome those problems. Certainly it shouldn't be a problem for an A&T.
  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-07 - 04:52:58
    UPDATE
    While I sort out the P2LAB and other boards I will just order these P2D2 and P2PAL pcbs in the meantime. While I will get 100 blank boards back I just don't expect to make them all up, just the first few to make sure they are 100%. At the same time I will get quotes back for assembled and tested P2D2s on 200 or so units. Even at this low volume I expect to get them for a good price especially if I go through JLCPCB & LCSC where I will only supply the P2 chips but they can dropship from China which also lowers the cost per unit to Europe and the USA and saves all that double handling. ErNa plans to distribute these for Europe and I guess the UK, and while Publison is handling the bulk order for the US and mailing them out, this is more of a Parallax community service that he is kindly providing for free for the moment. I know, I know, this really needs to be handled by Parallax ideally but while they are helping me with P2 chips at cost price or so, I have to do this off my own back. It is my intention to ship P2D2+P2PAL at no extra cost for those that have prepaid. This is one helluva P2 module!
  • Just continue moving fast.... So we don't have to wait 'till November to see if life is worth living!
  • UPDATE
    .... ErNa plans to distribute these for Europe....
    This is one helluva P2 module!

    True that is but how the you know what can I order these marvels in simple "do 1 2 3" steps, please ? I'm in Europe.

    @Peter Jakacki you're a master of suspense but I really need to get that pressure off me. Others might be in a similar position too.
  • MJBMJB Posts: 1,192
    Maciek wrote: »
    UPDATE
    .... ErNa plans to distribute these for Europe....
    This is one helluva P2 module!

    True that is but how the you know what can I order these marvels in simple "do 1 2 3" steps, please ? I'm in Europe.

    @Peter Jakacki you're a master of suspense but I really need to get that pressure off me. Others might be in a similar position too.

    I also was not with the EARLY-PAYERS, because I thought I want the whole bundle and not only the P2D2 in one shipping
    with the usually enormous shipping costs.
    Nobody expected it would take so long.

    So I signed informally in to buy a whole bundle, as soon as @Peter Jakacki names the price.
    But looks like this might be only in the second wave of productions.
    Dpends on how many are going to @ErNa I might be able to get one sooner or later ...



  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-08 - 15:30:11
    P2D2 A&T thoughts
    Now that the basic P2D2 module is only 1" wide with 50mil headers or SMD mount, I'm thinking about how these will be assembled and tested. My intention for myself is to mount the P2D2 flipped with 50mil female headers soldered to the component side so that it plugs into readily available pin headers. When the P2PAL option is also attached then the blank flip side which is now the top becomes the P2PAL component layer with the ESP32 and LEDs etc. I think that I if I get these boards A&Td that for the P2D2+ (P2D2+P2PAL) I would have them preassembled with headers since this is really the best way to mount them. The old P2D2 had bulky 100mil headers + RPi header and this P2D2+ flipped could still plug into a 100mil header board if need be. If you want to use it with an RPi though, then there is a HAT being made for it so there is no need for the old style header anymore.

    The P2LAB motherboard will have 50mil pin headers for the P2D2+

    I also need some P2D2s without the P2PAL just for SMD into some projects but the P2D2+ should ideally be assembled with headers. How does this sound?

    btw, besides the P2HAT for RPi which also has 50mil matrix prototyping area, there is the P2MAT which is a 50mil matrix 3.75" x 2.75" proto board as well.
    While I am waiting for some blank pcbs for testing I will be setting up with JLCPCB to A&T these boards the moment I can confirm that there are no changes necessary.

    The first photo shows the "old" P2D2r4 with the 100mil headers and then below it I have a P2D2 PCB cut down to the 50mil headers to represent the P2PAL with some components laid on top and the 50mil sockets and pins. The new P2D2 will be the same size as the P2PAL.
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  • For those who really really want those old style 100mil headers I will do a pcb that is exactly like the r4 version headers but only copper on the main pcb area. So this header pcb will serve not only as a 100mil header adapter where the P2D2 is surface mounted but because it is smd it can be a big double-sided 2oz copper heatsink as well. If you need the P2PAL as well then it can be mounted in similar fashion under the header board. So it's a real sandwich of two 1mm thick pcbs attached to the 1.6mm header in the sandwich.

    The P2D2 has so many options it is driving me crazy, and now the way the module can be used and combined is driving me crazy too.

    Something roughly like this:
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  • For those who really really want those old style 100mil headers I will do a pcb that is exactly like the r4 version headers but only copper on the main pcb area. So this header pcb will serve not only as a 100mil header adapter where the P2D2 is surface mounted but because it is smd it can be a big double-sided 2oz copper heatsink as well. If you need the P2PAL as well then it can be mounted in similar fashion under the header board. So it's a real sandwich of two 1mm thick pcbs attached to the 1.6mm header in the sandwich.

    The P2D2 has so many options it is driving me crazy, and now the way the module can be used and combined is driving me crazy too.

    Something roughly like this:
    I guess I missed this. Are you saying that the current design of the P2D2 won't plug directly into breadboard? Or maybe it never did and I wasn't paying attention?

  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-08 - 17:06:44
    The previous P2D2 versions had dual 20x2 100mil headers plus the additional 20x2 header for the RPi that was requested. But recently I had a rethink about the form factor as these headers were taking up a lot of pcb real-estate. I always had a dual 40x1 50mil header on the inside of these that was meant for smd mounting if the pcb was cut along the center of these 50mil headers. However on checking with pcb manufacturers this is not really possible to cut it yourself and get good results, they have to be milled when they are manufactured so as to cut the 50mil headers holes in half, thus "castellating" the pcb for smd mounting, just like the ESP32 has castellations.

    Ok, so I took another look at options, including using 50mil pin header which are far more compact than their 100mil cousins. I found a source for these at very good prices and the advantage they have over the 100mil headers is that they reduce the width of the P2D2 back from 1.7" down to 1", and are low-profile for a flush mounting. Now making the board slimmer I can also make it with 1mm thickness pcb instead of the standard 1.6mm so that when I sandwich a 1mm thick P2PAL to the back of it, it isn't too thick at all.

    I don't have the resources to manufacture different models and configurations but they can be combined in different configurations. This is always the problem when you have all kinds of flexible options. If I made the original P2D2, then that's what you get. But having just the slim module means I can get a reasonable quantity of the core P2D2 assembled and tested and bring the costs down. With the slim P2D2 I can surface mount it directly to a board, or use the 50mil pin headers, or surface mount it to the 100mil header board which might be handy for development work on the bench.

    For prototyping I have some 50mil matrix board in the works as well so you can plug the P2D2 into this with 50mil headers, and because of the smaller pitch you can even solder SOIC chips directly to the matrix board.

    OPTIONS OPTIONS OPTIONS OPTIONS - all possible with the slim 1" wide 50mil pitch P2D2

    The P2D2 was around before we ever had P2 chips since I created it as part of my documentation effort, as a reference design. The design has been upgraded several times since and I just want to get them out there now.
  • Thanks for the explanation.
  • P2D2 A&T thoughts
    Now that the basic P2D2 module is only 1" wide with 50mil headers or SMD mount....
    I think that I if I get these boards A&Td that for the P2D2+ (P2D2+P2PAL) I would have them preassembled with headers since this is really the best way to mount them....
    If you want to use it with an RPi though, then there is a HAT being made for it so there is no need for the old style header anymore.

    The P2LAB motherboard will have 50mil pin headers for the P2D2+....

    ... How does this sound?

    .... there is the P2MAT which is a 50mil matrix 3.75" x 2.75" proto board as well.

    While I am waiting for some blank pcbs for testing I will be setting up with JLCPCB to A&T these boards the moment I can confirm that there are no changes necessary.

    ... The new P2D2 will be the same size as the P2PAL.

    Ultimately, it's your vision, your product. You designed it based on years of experience and the use cases you envision for it. You've asked for suggestions, considered and reconsidered many (as it turned out countless) options. The final decision about its best form factor and functionality is also yours.
    Those who followed the process realize how hard it can be to put an end to it but it needs to be done one way or another.
    My take is that there are no uninformed customers here.
    I am speaking solely for myself but all I need to know is how can I become an owner of that product (and I am not even asking when would that be possible or how much would it cost). With the rest I entirely trust you 100%. How's that sound ?
  • P2D2 A&T thoughts

    ...

    I also need some P2D2s without the P2PAL just for SMD into some projects but the P2D2+ should ideally be assembled with headers. How does this sound?

    .

    Sounds fine. I can adapt to any size and pinout style as long as I can get my hands on one in the next month or so.
  • BTW I was the (naughty) soul who asked for the 0.050” headers to be on 1.000” centres. They were slightly wider than this at IIRC 1.045”.

    Now this actually makes the P2D2 pcb about 1.1” wide depending on the distance beyond the holes to the second set of castellated holes (if they are still on the pcb)??? And about 2.2” long?

    This certainly makes for a nice tiny board/module :)
  • Peter JakackiPeter Jakacki Posts: 9,628
    edited 2020-09-09 - 00:21:17
    STOCKING OPTIONS

    Getting small runs of blank pcbs are cheap these days so I can afford to have various adapters etc. However assembling a quantity of the P2D2 itself requires that I keep that part of it as standard as possible. If I ask for quotes on a fully loaded build and the price looks right then I will go ahead and get them made up and ship extra stock to Publison so that anyone in the US/Canada who wants one or ten can get them in a matter of days. Same too with Europe.

    The same is true of the P2PAL option and this can be stocked separately since it is a relatively easy matter to sandwich them together and solder up the edge pads with an iron or solder them together when you add the pin socket . But it may turn out that many may want the P2D2+ preassembled so this complicates the stock situation.

    Boards:
    P2D2 - Complete P2 system inc RTC and precision clock gen and USB serial supervisor with watchdog and smart reset etc.
    P2PAL - ESP32, 16MB HyperRAM, 8MB PSRAM, 6 LEDs+RGB, microSD, USB-C for alt mode HDMI (or VGA).
    P2PINS - 100mil headers inc 40-pin RPi "layer"
    P2HAT - An RPi HAT with prototyping pads + connection for a P2D2 (smd or 50mil pins)
    P2LAB - The P2D2 Motherlode board (mikroBUS, Ethernet, HDMI, VGA, A/V, USB, dual SD, DC, etc)
    P2MAT - A general-purpose 3.75" x 2.75" 50mil matrix prototype board
    P2USB - a tiny 8-pin vertical SIP USB serial module with the EFM8UB3 (watchdog, smart reset etc)

    Some use cases:
    Embedded P2D2 surface mounted to production PCB.
    Embedded P2D2 (optional P2PAL) sandwiched to a 100mil header breakout layer (P2PINS)
    Embedded P2D2 (optional P2PAL) mounted via pin headers to custom PCB or P2LAB or P2HAT
    Standalone P2D2 for development
    Standalone P2D2+ for development

    The original P2D2 had to be chopped down if you didn't want 100mil pin headers and those pin headers make the board 70% wider. But it turns out you can't really just chop the board down if you want to smd it, they have to be milled for castellations. This is the main reason for the slim P2D2 module.

    QUESTION: How many would want a P2D2+ preassembled?

  • David BetzDavid Betz Posts: 14,179
    edited 2020-09-09 - 01:38:57
    If by P2D2+ you mean P2D2+P2PAL then I'd like mine preassembled. As I've mentioned before, I'm happy to send more money to cover the P2PAL which wasn't part of our original orders. I'd also be interested in the P2LAB. Can the P2D2+ be plugged into the P2LAB or must it be soldered on?
  • David Betz wrote: »
    If by P2D2+ you mean P2D2+P2PAL then I'd like mine preassembled. As I've mentioned before, I'm happy to send more money to cover the P2PAL which wasn't part of our original orders. I'd also be interested in the P2LAB. Can the P2D2+ be plugged into the P2LAB or must it be soldered on?

    The P2LAB has pin headers and is all setup for a P2D2 to be plugged into it. All those who prepaid can have a P2D2+ preassembled for no extra cost as I have previously mentioned. If push comes to shove and they insist, they can always "donate" something for it :)

    I'm still moving connectors around on the P2LAB board but I will take the risk of showing what it "could" look like, but know that I will be refining the placements to get the right balance and allow this to be used for anything from benchtop development to enclosed industrial control. btw, there is not much in the way of components on the P2LAB except for the 24VDC to 5V switcher and maybe an RS485.
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