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Thread: Custom Teensy 3.6

  1. #1
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    Custom Teensy 3.6

    Hi everyone,
    I made a quick start into electronic design. Also I heard a lot about how good Teensy board is, since its schematic is available I decided that to design my custom Teensy 3.6. However, I have no previous PCB design experienced. I am working with Eagle CAD software and I find the required files (symbol etc.) for the MK66FX1M0VMD18 from NXP's website which is mentioned in schematic. However the MK66FX1M0VMD18 that I found and in the schematic one is not have same pins. So I can not continue to design. I add the symbols first one is from the NXP's website and the second one from the schematic. I need help about this situation and all responses are welcome.
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  2. #2
    Senior Member+ Frank B's Avatar
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    The 3.6 is definitely not a good start. I would really choose something much simpler as first design. I don't want to discourage you, but I'm pretty sure that it won't work....

    Maybe it makes more sense to start with a simple chip - maybe an ATMEGA in a DIL package.

    Edit: If you really want to start with the 3.6 : Buy one or two first - this way you can compare with it and bugfix your board way better.

  3. #3
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    @Frank B, Thanks for your precious response. I will consider your suggestion and I will check Atmega based hardware. But my question was, why are these two symbols is different although their code names are same, do you know something about this?

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Have you purchased and actually used even 1 real Teensy 3.6 board?

    Attempting to design your own PCB without even using a real Teensy 3.6 first would be crazy!

    Quote Originally Posted by erdemuysal View Post
    But my question was, why are these two symbols is different although their code names are same
    Whoever created the one on the left (orange color) is lazy, or lame, or stupid. Perhaps they are all three? Or maybe it was created by a bot, without any knowledgeable human checking the result?

    Here's is the 144 BGA pinout for the "VMD" version of the chip, from page 192 of the K66 reference manual:

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    Let's start in the upper left corner, which is pin A1. That pin is named "PTD7". But if you look at the orange symbol, they named it "A1". Lazy!

    But look across the first row. You can see the chip is 12 pins wide, so first row pins are A1 to A12. Admittedly A10 is "NC" for not connected, so you might expect A10 to not appear on the schematic symbol. But A11 is PTC3 and A12 is PTC2. Where are A11 and A12 on the orange symbol? Completely missing! So are 63 of the 144 pins. Lame & Stupid.

    Whoever created the orange symbol did a shoddy job. Nobody should use it. Anyone comparing to the K66 documentation can see it's clearly incorrect, missing many of the chip's pins, and not having any of them properly labeled, much less arranged in a sensible way for drawing a meaningful schematic.

    Now I will admit, the symbol on the right (which I created) is missing many of the pins as well. Teensy 3.5 & 3.6 do not make use of all the pins. I created that drawing to show how Teensy is connected. The unused pins were intentionally left off, so the schematic could be simpler and easier to read and understand.

    You might believe perhaps the orange one also intentionally left off some of the pins. But several of those pins are essential, like "RESET_b", "VSS", "PTA19" and "PTA18" on the right hand side of the chip. Likewise, it's missing everything below the H row, which has many more essential pins. Virtually every workable design would need to connect to those pins. The orange symbol is so flawed that it's useless.


    While I don't want to discourage you, I do wholeheartedly agree with Frank's advice. Designing a circuit board using a 144 pin BGA chip is not a beginner level project. If you looked at these 2 symbols and did not notice the orange one is missing many of the chip's pins and do not use any of the chip's actual signal names, perhaps that's a sign this sort of design is not a good place for you to begin learning.

    If you haven't actually used a real Teensy 3.6 yet, please do yourself a huge favor and begin the easy way. Gain some experience using the hardware before you attempt to create your own circuit board.
    Last edited by PaulStoffregen; 06-13-2019 at 11:37 AM.

  5. #5
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    Wow. You may well say that right. Thanks a lot, I noticed that I don't even know what should I consider before I start to design. Now I am going to work on some Atmega stuff and will back for Teensy one. I'd love to use it, but at least until I finish school and make money, it's a bit expensive to me. I will order a brand new Teensy later.

  6. #6
    Senior Member PaulStoffregen's Avatar
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    If you can't afford $29 for a Teensy 3.6 board, how will you pay for a 4 or 6 layer PCB to be fabricated? (a cheap 2 layer board is not good enough for this sort of design) Where will you buy the parts? Have you looked up their prices for single piece quantity? Have you factored in the cost for multiple packages to deliver all this stuff?

    How will you solder the BGA chip? Will you need to buy or borrow special tools? Or pay someone to do the very specialized soldering the BGA requires?

    Building a prototype yourself will end up costing much more than simply buying the $29 Teensy 3.6.

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    I actually thought that it can be 2 layers and I can solder with cheap soldering. But in the case of information, I realized that I need to learn much more thing from that. Do you have any advice for improving myself in the area of electronic PCB design? I am an electronics engineering student. During my studies, I focused on programming much more and I want to learn some PCB design.

  8. #8
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by erdemuysal View Post
    Do you have any advice for improving myself in the area of electronic PCB design?
    Start with a Teensy board. Or start with an Arduino board. But get an already-working board and learn how to use it. Use solderless breadoards or other "easy" construction techniques. Learn how these system work, and learn how to add your own circuits and make them work. Do this *before* you attempt to design your own PCB based on Teensy or Arduino.

    That is my advice. If you choose to ignore it, of course that's your choice to make.

  9. #9
    Senior Member brtaylor's Avatar
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    The ATmega 328 and similar are great through-hole packages as well - very straightforward to design a working PCB and you can stick with hand-soldering through-hole parts. The reference manual is relatively short and there are a ton of videos and other information online. I would use a solderless breadboard first to try building a working ATmega and then design a PCB for it.

    Moving into the world of building custom Teensy boards, I would start with the Teensy 3.2 reference design (https://github.com/thewknd/teensy-bo...0board%20clone) and see if you can fabricate that. You would be starting from a known working PCB design and cart of parts and simply working on fabrication skills. There's a lot of resources on this forum about custom Teensy boards, but I think the bottom line is that for you to be successful, you need to understand why the schematic is the way it is, rather than simply copying it. That requires some understanding of circuit design and building up experience designing and fabricating PCBs.

  10. #10
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    Quote Originally Posted by brtaylor View Post
    you need to understand why the schematic is the way it is, rather than simply copying it.
    I am exactly agreeing with these ideas and my purpose is in this way. I will apply your suggestions. I have an Arduino, I will be busy with that and do some stuff and then with its reference manual I will try to understand what is going on at the background before start design a PCB. Thanks, both of you.

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