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Thread: MINI54 and MK20DX256VLH7 use on other Teensyduino type projects?

  1. #1
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    MINI54 and MK20DX256VLH7 use on other Teensyduino type projects?

    Has anyone had any success using the MINI54 chip / MK20DX256VLH7 chip while making their own Teensyduino type of project?

    My hopes are to combine the audio board and Teensy into one board. Instead of having to mate the two with headers.

    Thanks for any insight into doing this!

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    Where did you look first? and however did you not find it? Mr Google is your best friend, Should you ever really wish to learn to how to learn. IMO

    D.
    Last edited by Docedison; 11-19-2014 at 05:15 AM.

  3. #3
    Senior Member Constantin's Avatar
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    Yup, have used them extensively, mostly because my needs were not quite met by the Teensy 3.x in its current form factor. Thankfully, Paul was nice enough to make three different versions of the Mini 54 available, I use the largest one. All my boards are dual-layer and when one is careful re: layout, pin assignments, etc. they do function well, even on a 2-layer board.

    Not sure why you'd want to reinvent the wheel re: the audio backpack, seems like a lot of work for very little gain. The current solution works, is relatively compact, etc. Your proposed solution would be relatively costly on a one-off basis but a good learning exercise, I suppose.

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    Trying to do this as we speak, but can't seem to get the chip to enumerate as a com port in the Arduino IDE even after pushing the bootloader button. it did see it on first boot up as a HID device but never attached a com port to it.....even after trying to load a serial related sketch to it.

    I've also reloaded teensyduino and everything works as a typical Teensy 3.1 would except for the fact that I can't enumerate a com port and therefore I can't open a com port to even get a Hello World reply...
    Last edited by rvogel; 11-19-2014 at 08:32 PM.

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    Senior Member Constantin's Avatar
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    Whenever I've struggled with behavior like this it was due to incorrect pin assignments like putting the Reset line on the wrong pin connector between the Mini 54 and the MK20. I'd go through Pauls troubleshooting guide and take a look at the power lines followed by watching reset with a scope to see what's going on there as you try to upload a program and/or press the reset button.

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    Quote Originally Posted by Constantin View Post
    Whenever I've struggled with behavior like this it was due to incorrect pin assignments like putting the Reset line on the wrong pin connector between the Mini 54 and the MK20. I'd go through Pauls troubleshooting guide and take a look at the power lines followed by watching reset with a scope to see what's going on there as you try to upload a program and/or press the reset button.
    I went through the MINI54 to MK20 sheet and verified the connections. I did add a reset button on the MK20 board and kept it high with a 10K resistor pulled up to VDD......do you think that pull-up might be having an effect?

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    Senior Member Constantin's Avatar
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    When in doubt, start with a working design. Then modify and cross your fingers.

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    Pulled the reset switch's 10K pull-up from the reset line and still no joy. This switch is tied to RESET on the MK20 and is not the program pushbutton for the MINI54. Here is the verbose reading I get from teensyduino when trying to load the teensy "Hello world" sketch from the teensy examples.

    Code:
    13:32:43: Device came online, code_size = 262144
    13:32:43: Board is: Teensy 3.1 (MK20DX256), version 1.03
    13:32:43: File "HelloWorld.cpp.hex". 14556 bytes, 6% used
    13:32:43: File "HelloWorld.cpp.hex". 14556 bytes, 6% used
    13:32:43: elf size appears to be 262144
    13:32:43: elf binary data matches hex file
    13:32:43: Code size from .elf file = 262144
    13:32:43: begin operation
    13:32:43: flash, block=0, bs=1024, auto=1
    13:32:43: flash, block=1, bs=1024, auto=1
    13:32:43: flash, block=2, bs=1024, auto=1
    13:32:43: flash, block=3, bs=1024, auto=1
    13:32:43: HID/win32: waiting for device
    13:32:43: HID/win32: waiting for device
    13:32:43: flash, block=4, bs=1024, auto=1
    13:32:43: flash, block=5, bs=1024, auto=1
    13:32:43: flash, block=6, bs=1024, auto=1
    13:32:43: flash, block=7, bs=1024, auto=1
    13:32:43: flash, block=8, bs=1024, auto=1
    13:32:43: flash, block=9, bs=1024, auto=1
    13:32:43: flash, block=10, bs=1024, auto=1
    13:32:43: flash, block=11, bs=1024, auto=1
    13:32:43: flash, block=12, bs=1024, auto=1
    13:32:43: flash, block=13, bs=1024, auto=1
    13:32:43: flash, block=14, bs=1024, auto=1
    13:32:43: sending reboot
    13:32:43: begin wait_until_offline
    13:32:44: offline, waited 12
    13:32:44: end operation
    13:32:44: redraw timer set, image 14 to show for 1200 ms
    13:32:44: HID/win32:  vid:045E pid:0772 ver:0113
    13:32:45: redraw, image 9

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    ....also verified on o-scope that I see communications on the USB lines at the mk20 pins 5 and 6, as well as, both sides of the resistors on those lines. Just to clarify, I do have an actual teensy 3.1 that works with the USB cable I'm using just fine.

    Reset line does go low when bootloader switch is depressed.

    Went through MK20 Teensy schematic again to compare. Only item omitted from my design is no VBAT connection since I'm using external RTC and the 16MHz crystal is not the same part number since I didn't locate that till recently

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    Recipe for the 'calamari' batter?.. <BFG>

    Doc

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    Pretty confident the issue is the crystal. O-scope on actual Teensy 3.1 has a nice 16MHz signal. Crystal I'm using does not.

    Instead of asking, I guessed on that part and used http://www.digikey.com/product-detai...83CT-ND/465171 instead. O-scope shows nothing. looks like the one used on teensy is a 8pF and the one I chose was a Series load. didn't see parallel caps like I'm used to seeing on an arduino crystal so I made the assumption that a series was what I needed.

    Schematic attached

    Click image for larger version. 

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    bootloader board that attaches to header....it is the TQFP-48

    Click image for larger version. 

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    Last edited by rvogel; 11-20-2014 at 11:55 AM. Reason: added bootloader drawing

  12. #12
    Senior Member Constantin's Avatar
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    Rvogel,

    Your post illustrated the issue - you did not start with known good design and experimented on your own from there. Rather, you put together something that you thought would work but didn't test in advance. Been there, done that, have a boxfull of PCBs to show for it. In short, you chose the wrong oscillator.

    You want this one with a 8pF capacitance You may or may not be able to make yours work if you modify the board and/or the software running the chip - the MK20 can be programmed to offer a range of load capacitances for crystals. By default, it expects to provide the capacitance associated with a nominal 8pF external crystal.

    As for DocEdison, the Calimari would be pretty chewy no matter how you prepared it.
    Click image for larger version. 

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    It was about 10' tall and 16' wide and contained about two months worth of newspaper. It glowed nicely at night thanks to flourescent paint and a battery of UV lights. Unfortunately, the auto-WB in the camera makes the paint simply bright, as opposed to glow-like. Still have to learn how to adjust the WB ahead of taking the pictures. The picture of our vampire pig (our first project) came out a bit better.

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    My Avatar features a head shot of this years' creature, a 20'+ long dragon. Fierce!

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    Need to find a way to integrate Teensy's into these projects. The dragon consumed a months worth of paper, 4+ gallons of glue, etc. and was my first return to welding since college.
    Last edited by Constantin; 11-20-2014 at 02:54 PM.

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    and just to verify. no external caps needed....? samples of the new crystal headed my way.

  14. #14
    Senior Member Constantin's Avatar
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    Quote Originally Posted by rvogel View Post
    and just to verify. no external caps needed....? samples of the new crystal headed my way.
    No external caps needed as long as the load capacitance for the crystal is 8pF

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    Interesting to note something.......

    Since The board I have is about to be changed anyway I thought I would look at something. I have some other 16MHz crystals, as well as the original one I was trying to use. Some are 20pf and some "Series". I noticed that all of them show a nice 16MHz signal when the bootloader button is depressed, but then they shut off when load is complete...??

    Is that normal or would that indicate a different issue?

    I used many different settings for the OSC0_CR in the mk20dx128.c file to try and set load capacitance accordingly. No matter what the settings, I always got the same signal...good during boot and then it shuts off.

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    attached is the board I'm building that is teensy 3.1 based. I've purchased quite a few of the actual teensy boards and wanted to make something that was versatile for adding sensors and other wired projects. I originally was going to use the separate bootloader CCA, but after all of the research and great support that I see throughout this site, I feel it only makes sense to add the MINI54 on the processor board in order to continue to give back to Paul and the community's efforts through the purchase of that chip for each board.

    Hopefully the correct crystal will solve my issues...Click image for larger version. 

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