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Thread: YATB - Yet Another Teensy Board :D

  1. #31

    Re: YATB - Yet Another Teensy Board :D

    Thanks for the information, will have to take a look.

    It will be curious how much of this is already handled within the Adafruit BNO055 board
    It no not only has the sensors, but also an m0 processor that does a bunch of the processing. I used one of these on the first board I assembled, and I used the sparkfun board on this updated board. My board is setup to mount either of them.
    Last edited by KurtEck; 01-28-2016 at 02:03 PM.

  2. #32
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    Re: YATB - Yet Another Teensy Board :D

    You've got some good ideas in the works!

    I feel your pain with the Odroid and the USB. I remember getting quite bothered with the PrimeSense troubles I had on the USB2.0 ports of the XU3 I had to switch to the USB3.0 port to get all the data I was requesting.
    01001001001000000100110001101111011101100110010100 10000001010010011011110110001001101111011101000111 0011

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  3. #33

    Re: YATB - Yet Another Teensy Board :D

    Thanks, Hopefully can get stuff to work well.

    Right now debugging the initial Gyro stuff. I first tried testing it by adding a simple test to my AXTest program that read in the 12 bytes from the controller and printed the values when they changed. So far I am not getting values that I expect, which I verified by plugging in the replacement Arbotix Pro, and checked the values that were coming out from it....

    So I think I will instead run a simple subset of the logical controller sketch that only does the gyro/plus output when things change and debug it first there...

    In either case it does not look like the values returned make it look like it is easy to use, to figure out things like the actual positions... So I can see why it would be very nice if I can add in the data fusion... Again looks like the Adafruit board has some nice going for it!


  4. #34

    Re: YATB - Yet Another Teensy Board :D

    Side Note: I want to get back to this, and build the new one with the Adafruit IMU. But have other projects both Robotics/electronics (Rebuild PhantomX, Serial communications to Arbotix Pro, update to new ROS hexapod stuff...) as well as other (plant trees, prepare garden), which will keep me busy for probably several weeks. Why I mention this, is I probably have time to make a new revision of board, before building the next one...

    And, I keep wondering about: AX-BUS, currently my Teensy is driving it at 3.3vs. The pins are 5v tolerant. So far I have not noticed problems with this, but earlier I have had the servo reset to 1 issue (although I don't think I saw any more with the Teensy driving it versus USB2AX or Arbotix-M). But I wonder if I would be better off converting this signal to 5vs? Note: Currently using the Teensy's half duplex support of the USART where I only connect up to TX pin.


    1) Punt: Obviously the easiest, after all it is only my board to play with, although others can use if they want.

    2) Convert single pin to 5vs (bi-directional). On the board I have a pin for the OLED that is output only that is converted using an SN74LV1T125 but I am pretty sure that is output only. Options for Bidirectional level shifters?

    a) Something like a TXB0104 or TXS0104? I used breakout boards with the TXB... example currently connecting ODroid to Arbotix Pro, and the ODroid level shifter board for XU4 uses the TXS... Have not looked yet what difference are. Also wondering if there is an
    equivelent for 1 or 2 bits...

    b) Something like the SN74LVC1T45? - Bidirectional, but uses a direction pin (high is output) - Could probably use the Teensy support (Set output pin) to do the switching... But in this case it does not update the direction in the USART... But my same code that switches the direction bit in the port could update this as well. Or as suggested on Teensy forum, maybe instead us the
    74HCT126, which may have the direction bit working better?

    3) Use both TX/RX pins, probably some circuit like what Robotis shows in the AX documents.

    4) Similar to 3) found circuit that some are recommending for RPI to AX Bus using an SN74LS241, which is a 20 pin octal buffer, which can do 4 channels, where if I am reading it correctly, the direction bit is opposite on some of the channels. Would be nice to find a similar chip that does fewer channels, as to reduce the size.

    Space considerations: If I add something like the SN74LS241, it would probably require me to make some room on the board. For me some of the options include: Remove 3.3v VR. I really don't need it as I have the option to use one built into Teensy. Also might drop the option for SParkfun IMU as I like Adafruit better. Note: Prefer parts that are reasonably easy to hand solder.

    Last edited by KurtEck; 02-20-2016 at 10:05 AM.

  5. #35

    Re: YATB - Yet Another Teensy Board :D

    Thinking of going with the SNLS241 I mentioned above, as it only needs one chip. Although I added decoupling capacitor...
    Still cleaning it up some, but 3d model currently looks like:

    Click image for larger version. 

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    Actually I am sort of curious about the use of this for the RPI. It only has one VCC pin, which they hooked up to +5v, which I believe would be good for coming out of the TX going to it and the AX-BUS, but on the RX side, wouldn't the output of the buffer be +5v? Not a problem for Teensy, but did not think RPI likes that...

    But just playing around.

  6. #36

    Re: YATB - Yet Another Teensy Board :D

    More like notes to myself, so I don't have to keep asking myself the same question above...

    Earlier with my latest smaller board, I used a different approach to control AX Buss, as I also want that board to support the Teensy LC, which is only 3.3v (i.e. not 5v tolerant). So back at posting 25 of this thread, I used a transister like a 2n7000, to hopefully do this translation, which I have not tested out yet, should order parts and try this board out! The portion of the schematic looked like:
    Click image for larger version. 

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    It would have been easier to update the Teensy Arbotix Pro board the same way, but jwatte's thread up on PJRC forum made me curious, about using the TX enable capability that Paul built into the Serial library, so I went with the SNLS241 approach. The DXL Portion of this schematic now looks like:
    Click image for larger version. 

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    Hopefully I did not screw up too badly as ordered a set from OSHPark.

  7. #37

    Re: YATB - Yet Another Teensy Board :D

    I don't get why you have R4 in the schematic. It seems like it will render the level translation moot.
    When JAX is 5V, the AX will see 3.3V + (5V-3.3V)*(10K)/(10K+150) or about 5V.

  8. #38

    Re: YATB - Yet Another Teensy Board :D

    Quote Originally Posted by jwatte View Post
    I don't get why you have R4 in the schematic. It seems like it will render the level translation moot.
    When JAX is 5V, the AX will see 3.3V + (5V-3.3V)*(10K)/(10K+150) or about 5V.
    Thanks jwatte,

    R4 - The idea was for T3.2 did not need other circuit so could just populate it (and not transistors plus PUs). For LC I need voltage going to processor to be 3.3v so use the transistor plus the two PU resistors and don't populate R4. But maybe better off for either processor to go that route.

  9. #39
    Join Date
    Sep 2010
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    Re: YATB - Yet Another Teensy Board :D

    I used the same 74_1G125/74_1G126 combination as the OpenCM9.04 for my assorted projects to do both the full-duplex to half-duplex and 3.3V/5V level translation. Pretty much the same buffer as the one you linked earlier, but available in a smaller footprint and not going all the way down to 1.2V.
    Attachment 6458

    Also mentioned elsewhere is the low-temp solder paste, $20 heatgun, and cheap stencil method of assembly that is ever so much easier than trying to solder SMD parts by hand.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
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  10. #40

    Re: YATB - Yet Another Teensy Board :D

    Thanks tician,

    I will take a look at those chips if I decide I need to change either of these boards. If I were to hand solder them, probably the 353 variety would be fine, like: and

    I may have to try out that paste you mentioned, I don't have the heat gun, but I do have one of the Sparkfuns hot air rework stations, Which I have used a couple times to remove parts. I should maybe try at some point to attach parts. I always wonder how you keep the parts in place when you blow hot air over them...

    Thanks again

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