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Thread: Any Plans for a Teensy Board with Bottom Pads on Top?

  1. #26
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    Quote Originally Posted by PaulStoffregen View Post
    So far, every Teensy has been 0.7 inch (17.8 mm) wide. Wouldn't that mean growing the width to 0.8 inch (a 14% increase)?
    Yes and no big deal, as I see it, considering the added convenience. Also, if there are plans for future boards having even more I/O pins, this would be a "relatively" painless way to go. And for a board with "many" additional I/O pins, then a 2nd parallel row of through-hole pins along the bottom. To me, all in all, much better than any of those tiny, tiny multi-pin connectors other people have mentioned. But it's just a thought.

    tonton81
    Nobody will want a klondike bar sized teensy over a single user's opinion. His concern is breadboard friendliness, whereas it doesnt matter in project use for 99% of others.
    To me, "breadboard" use is far behind anything at all practical.

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    @ tonton81 - for what it's worth most of my projects start on a breadboard, and then migrate to some form of protoboard so the compatibility is a big deal for my use. That said I feel there is very much an upper limit to how many pins you should be attempting to put into a bread board before you have to bite the bullet and do something more robust (for me about 25-30 jumpers). So a hypothetical T4++ with 40 or more pins down each side just sounds like a recipe for lots of tech support support posts here from people trying to actually use all those pins in some massive hairball.

  3. #28
    Senior Member PaulStoffregen's Avatar
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    I tend to agree, even Teensy 3.5 & 3.6 having 42 breadboard accessible I/O signals is a bit much. Standard breadboards have 63 columns. With only 39 left over, you can't really build up circuitry that uses so many signals.

    Even if you use something like this, you've got 39+63+63 columns. That's an average of just 3.7 columns per I/O signal, which is just barely enough space to make almost anything useful.


  4. #29
    Hi

    I don't see a breadboard useful to make a complete setup, but very useful to setup a subset for testing.
    For example : If I use rotary encoders with a push button I don't need to connect all rotary encoders and certainly only 1 or 2 pushbuttons.
    The same for testing mux connected inputs --> testing can be limited.

    Is a double row pin's possible with the "cheap" single layer PCB's?

  5. #30
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    Quote Originally Posted by PaulStoffregen View Post
    I tend to agree, even Teensy 3.5 & 3.6 having 42 breadboard accessible I/O signals is a bit much. Standard breadboards have 63 columns. With only 39 left over, you can't really build up circuitry that uses so many signals.
    I am now convinced that anything longer than Teensy 3.6 is too much, but as short as Teensy 3.2 is too little. I'm very happy with the Teensy 3.6 on a standard breadboard. My motor drivers, IMUs, power supply, pixy camera, etc. are separate modules anyway and the standard breadboard acts as a good bus. I'm able to stack many SPI device (up to 3) on the same breadboard rows.

    As @oric_dan suggested, a second parallel-row of through-holes is an excellent solution for the upping the bottom pads. As long as the width fits on a breadboard. A standard 0.1 inch arrangement makes it simple to solder in headers like I do with T3.6 AREF, A10, A11, Reset, Program, etc. This is simpler than having a micro-connector for pin expansion because a special cable is not required.

    Still a few micro-connectors for a TFT or other SPI devices is an excellent idea. That'll simplify circuits. Maybe moving some of the Teensy components on the bottom like a Maple Mini might give you more real estate on top.

    Hopefully PRJC is not abandoning the breadboard friendliness form factor. It seems to be catching on. Others are going with it. Maple Mini was probably the first in the 32bit class, but they failed in the implementation (terrible documentation and so-so libraries). PRJC seems to be doing very well. I have more Teensy products than Arduino Due and Parallax combined. Would the Teensy be doing better if it used the Arduino form factor? (as in Uno & Due)
    Last edited by randomvibe; 12-25-2017 at 07:36 PM.

  6. #31
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    Quote Originally Posted by AlainD View Post
    Hi
    I don't see a breadboard useful to make a complete setup, but very useful to setup a subset for testing.
    For example : If I use rotary encoders with a push button I don't need to connect all rotary encoders and certainly only 1 or 2 pushbuttons.
    The same for testing mux connected inputs --> testing can be limited.

    Is a double row pin's possible with the "cheap" single layer PCB's?
    Single-layer pcbs = out of the question, probably also for 2-layer; but extra pins along the edges may make routing slightly easier.

    No one in their right mind would build a system on a breadboard and try to connect up 40-60 I/O pins to external cktry. Better for testing than deployment. Test and then move to something more permanent where the wires won't fall out. Unfortunately, that pattern of construction is a very bad carry-over from Arduino projects. Must be 100s of Arduino projects shown built on breadboards. Hopefully, Teensy people know better.

  7. #32
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    Would the Teensy be doing better if it used the Arduino form factor?
    If by this you mean UNO-formfactor, then it wouldn't be a "Teensy" anymore. However, if Paul keeps designing new boards with oodles more I/O pins, then he'll have to bite the bullet in some manner or other.

    ASIDE: just as a point of information, I have a T3.1 board going into my new quadruped walker that I put together the past 2 days, and I'll change to a T3.6 board once I get another one of those built up.

    I've actually been a big fan of the UNO-formfactor for years, and made my own pcbs for mounting Teensies so I could attach regular Arduino shields to them. (these are not for sale, BTW). I've since done the same thing for T3.5,3.6 with a slightly larger pcb, but still UNO-formfactor.

    https://forum.pjrc.com/threads/27519...ll=1#post61951

    I personally favor the small "Teensy" formfactor, but also some Tindie/whatever people selling larger boards for project use that the Teensies can be mounted on.

    EDIT:
    I thought I would just pass this along, FWIW. Some people solder right-angle headers to the smt pads on the bottom of the T3.x modules, and connect directly to those, or else solder the r-a headers into pad holes aligned on a pcb. What I do on my pcbs (as referenced) is first solder bare wire-wrap wire to the smt pads, pass those wires through the pad holes in my pcb, and then solder in place. This makes a permanent installation, but that's ok for me. I also bring out the Reset pin the same way on the T3.1,3.2 modules.
    Last edited by oric_dan; 12-25-2017 at 08:48 PM.

  8. #33
    Senior Member+ Theremingenieur's Avatar
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    Using one GPIO pin per button is in many cases also an inefficient design. Buttons may be organized in a matrix, potentiometers can easily be multiplexed. In a next step, many HMI functionality can be delegated to a single touch screen. If a huge number of digital and analog inputs was really inevitable, I'd rather go for logically grouped subsystems around cheap Teensy LCs as concentrators, and have everything hooked to the main CPU via I2C as tonton81 suggested: https://forum.pjrc.com/threads/46559...duino-teensies.

  9. #34
    Senior Member+ defragster's Avatar
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    How about just adding 0.05 inches?

    Click image for larger version. 

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  10. #35
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    Quote Originally Posted by defragster View Post
    How about just adding 0.05 inches?

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    I like the additional row, but I would prefer a whole 0.1 inches to solder in a male or female header. The 0.05 inches would still obscure a breadboard row, so might as well go with 0.1 inches.

    I hope PRJC keeps the microSD slot. It saves me a bunch of wiring and its close proximity to the CPU keeps a clean SPI transmission path.
    Last edited by randomvibe; 12-26-2017 at 04:54 AM.

  11. #36
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    you guys rant for breadboard capability, but agree to double rows? this thread is for the birds lol

  12. #37
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    Quote Originally Posted by tonton81 View Post
    you guys rant for breadboard capability, but agree to double rows? this thread is for the birds lol
    I think of the Teensy as a compact and rectangular, self contained "system on a module" with 0.1 inch pins that will integrate on a custom PCB, or expansion shield, or just a breadboard. Just like any other chip with 0.1 inch pins. What else should it be if not rectangular? If the future Teensy was released with double rows, would you buy it? I think those who don't need the additional row can just ignore like they already do for many of the extra pins. And for those customers who do need it, it's there.

  13. #38
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    you obviously didn’t understand the concept between breadboard and double rows.

  14. #39
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    For instance, I still pickup the Teensy 3.6 inner pins (AREF, A10, A11 etc.) with upper male headers while the side rows are anchored to a breadboard.

    Similarly, on the concepts above, the outboard-most rows would apply to a breadboard, and the inner row(s) would be picked up with upper headers.

  15. #40
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    why stop there...
    have the inner pads headered downwards and 90 degree pin offset the sides, make it look like teensy has wings lol

  16. #41
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    Quote Originally Posted by tonton81 View Post
    ... this thread is for the birds lol
    Quote Originally Posted by tonton81 View Post
    ... make it look like teensy has wings lol
    Seeing a trend here ... Wingsy - the Teensy that can fly.

    My favorite Teensy was the K66 PROTO DESK pre-Beta T_3.6. Not just cause it was free, but it came with a nice base to sit on my desk and plug stuff into without the cable dragging it off. Somebody should do a Kickstarter on an OSH Reference board version - I'd buy 1 or 2.

    Keeping it compatible and small define the direction - an UNO/MEGA (or Klondike bar) sized make it neither of those. And even with a second version would it go smaller for CPU power users or bigger for proto type users and is that PROTO DESK or Protoboard

  17. #42
    Senior Member PaulStoffregen's Avatar
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    @tonton81 - There's no need to get upset. I see this mainly as a brainstorming session. We have this conversation in the lead-up to every new Teensy model.

    Quote Originally Posted by defragster View Post
    How about just adding 0.05 inches?

    Click image for larger version. 

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    Please let me explain how the Teensy panels are designed for manufacturing. Hopefully a picture will help.

    Click image for larger version. 

Name:	panellayout.jpg 
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    Now the panels don't necessarily *have* to be made this way, but this shape is the result of years of gradually refining things with the contract manufacturers we use (PJRC doesn't have its own pick & place or reflow machines).

    The left and right side of each Teensy are made by routed slots in the panel. The top and bottom are V-score in the panel, which a machine uses to cut the panel apart after it's fully built. V-score can't be used along the edge with the USB connector, because it overhangs the edge of the PCB.

    The rigidity of the panel is a big issue for manufacturability. The pick & place machine moves very fast. If the panel flexes or vibrates, they have to run slower or risk parts shaking loose or off-center. Years ago this was an issue when we had longer slots. As you can see in the photo, we redesigned the panels to use short slots. A big unused strip in the center of the panel acts as a stiffening bar. When we added that, it dramatically reduced the vibration during assembly. It's one of many little refinements we've made over the years.

    Another little feature you might notice in the picture are the 6 tooling holes in the edge of the panel. Currently we used only 2 of these. The contract manufacturer has a jig that was specially made for Teensy which pins that fit those 2 holes, and a spring loaded horizontal clamp on the other side. Without such a jig, they need to carefully align each panel to the solder paste screen. The jig lets them do this alignment once per run, and they can put extra time & effort into getting it really accurate if it's done only once. Then each panel gets placed quickly and easily with excellent repeatability thanks to the jig.

    Just because we have a very well refined process doesn't necessarily mean we're forever locked into doing things just one way. But I think anyone can see how requiring one or both of the long sides to have routed slots rather than V-score is a huge change to the way we do the manufacturing!

    A few years ago when Particle Photon (then "Spark") made their board with castellated edges, everyone was asking for this feature. But it requires using slots the define nearly all edges of the board, with "mouse bite" tabs. I saw those guys at a Hackaday event and asked if they'd had issues with the panel rigidity. They didn't answer with any specifics, but it was pretty clear that had been a big pain point. They wouldn't say what they'd done to deal with the issue. Maybe they've made some sort of carrier to secure it during pick & place? Maybe their panels are much smaller? Or maybe they've just tuned their placement process (likely running slowly) and just accept a higher failure rate or more rework?

    On a personal level, I like to spend my time focusing on developing the software side and helping people get their projects working. Documentation is also a big goal, though you might not always know that from the sorry state of many of the web pages. Still, I *want* to work much more on that side.

    Experience has shown that manufacturing problems absolutely kill any hope for software development & documentation, and even support suffers pretty badly. It's also incredibly stressful. Maybe this would be difference it PJRC was a huge company, but the reality is we're just 4 people and a couple contract manufacturers. Even with things as well refined as we have them now, problems happen all the time. It's just a fact of life in manufacturing anything. For example, just a few days ago we had a high failure rate in part of a batch. The bed-of-nails test just gives a pass vs fail. To actually diagnose *why* they failed requires quite a lot of my attention. Let me tell you, this has a way of suddenly becoming the very most urgent thing when we have customers waiting! In the case last week, it turned out a few of the PCB panels with marked defects (every panel gets electrical test at the PCB manufacturer) got built by mistake. Nobody noticed the remnants of the Sharpie X marks. I didn't even see them while handling the boards, until after I'd gotten info from the tester and was looking around the boards under the microscope! But ultra-urgent problems aren't always a quality issues. Pins starting to wear out and sticking on the bed-of-nails testers are another one that comes up occasionally. But just as often, something comes up that's entirely new and requires "drop everything" immediate attention to solve, if we're going to get everyone's orders shipped.

    So while I'm not saying absolutely no to ideas like castellated edges, I do have a very strong desire to stay with this well tested panel design. Getting another jig made isn't too bad, under $1000 as I recall. But a panel using almost all routed slots with only small mouse bit tabs to hold the boards is a direction PJRC almost certain will not go.

  18. #43
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    Quote Originally Posted by defragster View Post
    My favorite Teensy was the K66 PROTO DESK pre-Beta T_3.6. Not just cause it was free, but it came with a nice base to sit on my desk and plug stuff into without the cable dragging it off. Somebody should do a Kickstarter on an OSH Reference board version - I'd buy 1 or 2.
    Also my favorite, unfortunately it is back to PJRC. For that reason I got me 3 K66 OSH Reference boards (seems to be similar to Proto board) but now, because Paul decided not add part numbers, I have to 'reverse' engineer the proper parts. OK, it should be possible, (at least for R and Cs, but the Xtal?)

  19. #44
    Senior Member+ defragster's Avatar
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    Paul - castellation would clearly muck with your established system - and reduce usable PCB's per panel - maybe 16 or 20 instead of 24. Could alternate PCB's rotate 180 in some fashion and still be assembled to maintain half the V-score? It hurts protoboard use some and changes that edge shape/size - but gives quick access to 20+ new signals in some fashion pins/sockets/wires - maybe more lift-proof than pads? Or just make it two full rows and design it for DIY cutting.

    Quote Originally Posted by WMXZ View Post
    Also my favorite, unfortunately it is back to PJRC. For that reason I got me 3 K66 OSH Reference boards (seems to be similar to Proto board) but now, because Paul decided not add part numbers, I have to 'reverse' engineer the proper parts. OK, it should be possible, (at least for R and Cs, but the Xtal?)
    When I first saw the TODO was dropped -- I was wondering if good photos or hand reading of the parts on my Proto as needed might help finish? I could send it to you?

  20. #45
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by WMXZ View Post
    at least for R and Cs, but the Xtal?
    Any 16 MHz crystal the right size (3.2 by 2.5 mm) should work. Ideally you want 8 to 10 pF rating. I believe all the ones made in that physical size have approx that capacitive load spec.

  21. #46
    Quote Originally Posted by PaulStoffregen View Post
    @tonton81 - There's no need to get upset. I see this mainly as a brainstorming session. We have this conversation in the lead-up to every new Teensy model.



    Please let me explain how the Teensy panels are designed for manufacturing. Hopefully a picture will help.

    Click image for larger version. 

Name:	panellayout.jpg 
Views:	73 
Size:	288.2 KB 
ID:	12379

    Now the panels don't necessarily *have* to be made this way, but this shape is the result of years of gradually refining things with the contract manufacturers we use (PJRC doesn't have its own pick & place or reflow machines).

    The left and right side of each Teensy are made by routed slots in the panel. The top and bottom are V-score in the panel, which a machine uses to cut the panel apart after it's fully built. V-score can't be used along the edge with the USB connector, because it overhangs the edge of the PCB.

    The rigidity of the panel is a big issue for manufacturability. The pick & place machine moves very fast. If the panel flexes or vibrates, they have to run slower or risk parts shaking loose or off-center. Years ago this was an issue when we had longer slots. As you can see in the photo, we redesigned the panels to use short slots. A big unused strip in the center of the panel acts as a stiffening bar. When we added that, it dramatically reduced the vibration during assembly. It's one of many little refinements we've made over the years.

    Another little feature you might notice in the picture are the 6 tooling holes in the edge of the panel. Currently we used only 2 of these. The contract manufacturer has a jig that was specially made for Teensy which pins that fit those 2 holes, and a spring loaded horizontal clamp on the other side. Without such a jig, they need to carefully align each panel to the solder paste screen. The jig lets them do this alignment once per run, and they can put extra time & effort into getting it really accurate if it's done only once. Then each panel gets placed quickly and easily with excellent repeatability thanks to the jig.

    Just because we have a very well refined process doesn't necessarily mean we're forever locked into doing things just one way. But I think anyone can see how requiring one or both of the long sides to have routed slots rather than V-score is a huge change to the way we do the manufacturing!

    A few years ago when Particle Photon (then "Spark") made their board with castellated edges, everyone was asking for this feature. But it requires using slots the define nearly all edges of the board, with "mouse bite" tabs. I saw those guys at a Hackaday event and asked if they'd had issues with the panel rigidity. They didn't answer with any specifics, but it was pretty clear that had been a big pain point. They wouldn't say what they'd done to deal with the issue. Maybe they've made some sort of carrier to secure it during pick & place? Maybe their panels are much smaller? Or maybe they've just tuned their placement process (likely running slowly) and just accept a higher failure rate or more rework?

    On a personal level, I like to spend my time focusing on developing the software side and helping people get their projects working. Documentation is also a big goal, though you might not always know that from the sorry state of many of the web pages. Still, I *want* to work much more on that side.

    Experience has shown that manufacturing problems absolutely kill any hope for software development & documentation, and even support suffers pretty badly. It's also incredibly stressful. Maybe this would be difference it PJRC was a huge company, but the reality is we're just 4 people and a couple contract manufacturers. Even with things as well refined as we have them now, problems happen all the time. It's just a fact of life in manufacturing anything. For example, just a few days ago we had a high failure rate in part of a batch. The bed-of-nails test just gives a pass vs fail. To actually diagnose *why* they failed requires quite a lot of my attention. Let me tell you, this has a way of suddenly becoming the very most urgent thing when we have customers waiting! In the case last week, it turned out a few of the PCB panels with marked defects (every panel gets electrical test at the PCB manufacturer) got built by mistake. Nobody noticed the remnants of the Sharpie X marks. I didn't even see them while handling the boards, until after I'd gotten info from the tester and was looking around the boards under the microscope! But ultra-urgent problems aren't always a quality issues. Pins starting to wear out and sticking on the bed-of-nails testers are another one that comes up occasionally. But just as often, something comes up that's entirely new and requires "drop everything" immediate attention to solve, if we're going to get everyone's orders shipped.

    So while I'm not saying absolutely no to ideas like castellated edges, I do have a very strong desire to stay with this well tested panel design. Getting another jig made isn't too bad, under $1000 as I recall. But a panel using almost all routed slots with only small mouse bit tabs to hold the boards is a direction PJRC almost certain will not go.
    mmm a huge I/O Teensy with 30 pins on each side would give 3 pcb's instead of 4. It would be breadboard testable, fit on a Perma-Proto Half-sized Breadboard PCB and be usable with single layer PCB's.

    A side question : How often are the bottom pads used in applications?

    Alain

  22. #47
    Senior Member PaulStoffregen's Avatar
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    Yes, the board could become 30 or even 32 pins per side, instead of the 24 we have now. We’d get 18 per panel instead of 24. Manufacturing cost would go up somewhat.

    But everyone wishing to install Teensy inside of some project would have to deal with an even longer board, even if they don't need the extra signals. Is that worthwhile?

  23. #48
    Quote Originally Posted by PaulStoffregen View Post
    But everyone wishing to install Teensy inside of some project would have to deal with an even longer board, even if they don't need the extra signals. Is that worthwhile?
    No off course not. For me such a large Teensy isn't for everybody, but I see quite a few things on the forum that are "needing" large numbers of I/O.
    Although using slave LC's is maybe a better option for those.

  24. #49
    Senior Member+ Theremingenieur's Avatar
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    Quote Originally Posted by AlainD View Post
    No off course not. For me such a large Teensy isn't for everybody, but I see quite a few things on the forum that are "needing" large numbers of I/O.
    Although using slave LC's is maybe a better option for those.
    I second that. From reading these forums, a vast majority of users seems to be fine with the current form factors. Those who need more have already alternatives from using slave devices to building their own custom PCBs.

  25. #50
    Quote Originally Posted by Theremingenieur View Post
    I second that. From reading these forums, a vast majority of users seems to be fine with the current form factors. Those who need more have already alternatives from using slave devices to building their own custom PCBs.
    Well it depends. slave devices or custom PCB's are currently a big extra step for people that want to start.

    A 3.2++ (or even LC++, but I think it's already has all IO to the side pins) with more I/O on the side pins could be a nice starting point for users and a nice slave unit for those that will need more. Maybe adding a few mux chips on the board.

    For me it's a trade off in extra sales versus extra cost for the extended pcb version (money, time, troubleshooting,...) for pjrc.

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