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Thread: PhantomX using a Teensy 3.1

  1. #251

    Re: PhantomX using a Teensy 3.1

    Thanks I will have to try out the regulator again and see if anything is responding...
    UPDATE: Connected up to 3s lipo, verified +12.4v to terminal. Checked output of VR at 4.9v Actually it is a DC/DC switching regulator... And Teensy appeared to work.

    Since Radio shack carries LM386 chips, I may try breadboard circuit, maybe their minimal setup with two caps and a resistor and maybe a variable resistor. If it works OK, may update my circuit with this or decide some fixed resistor value for the variable one...

    Thanks again
    Last edited by KurtEck; 05-10-2015 at 02:51 PM.

  2. #252

    Re: PhantomX using a Teensy 3.1

    A 4.7/4.7 kOhm resistive divider is usually a fine input stage for an amplifier like this.
    Hope it works out for you!

  3. #253

    Re: PhantomX using a Teensy 3.1

    Thanks, I have been playing with it. Been posting more about it on Teensy site:

    With the hookup I was receiving nothing. I looked at signal using Saleae LA (with analog) and saw that the signal coming into the voltage divider centered on about .6v (half of the 1.2 internal voltage reference). Was advised to put a 10u Cap in series between DAC and voltage divider, which bring the signal to be centered at 0v...

    Good news is currently can get some sound, but currently mostly sounds like noise. I am wondering about the hookup as I hooked 2 probes up this time one at input to divider and 2nd to + pin of speaker. And it looks like I am only getting plus side?

    Click image for larger version. 

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    Will play more later...


  4. #254

    Re: PhantomX using a Teensy 3.1

    I now have a working circuit. A couple of problems, one the Analog hookup for speaker showed truncated. The issue is that LA does not show negative values, so changed probe point to output of LM386. Also found I needed a decoupling capacitor on the chip. Datasheet did not show one, but should have done so on GP...

    So now with the Audio library test program, I can get a Gong sound

    Click image for larger version. 

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    Also played a little with Diptrace to see if I could put the extra parts on including speaker instead of buzzer (15mm instead of 12)

    Still need to play around some more, but looks like it could fit:
    Click image for larger version. 

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    Again just doing this for fun...

  5. #255

    Re: PhantomX using a Teensy 3.1

    Good for you! Did you solve the noise problem? Was that the de-coupling capacitor?

  6. #256

    Re: PhantomX using a Teensy 3.1


    Yep it was the lack of the DE-coupling capacitor. Also I am not sure how much this mattered, but the schematics in their datasheet showed a .05uf cap in it. Radioshack did not have these they had some .1uf, which I used. Over on pjrc I was reminded of some stuff I learned back in my last circuit analyses class that I took back in college many many years ago. That if I put two of the .1uf caps in series, you end up with a .05uf cap equivalent, which I did as well.

  7. #257

    Re: PhantomX using a Teensy 3.1

    In general, more is usually better (unless this is part of a low-pass filter circuit) so you could probably also put them in parallel for four times the goodness :-)

  8. Re: PhantomX using a Teensy 3.1

    Hello All,

    I recently purchased a Lynxmotion Phoenix hexapod and been doing a deep dive on all the IK calculation math. I really had a desire to code everything from scratch so I could fully understand the math. I've spent a fair amount of time studying KurtE's code (Thanks!). My hardware setup is Phoenix frame, HS645-MG servos, SSC-32 servo driver and a Teensy 3.1 MCU running at 96Mhz clock.

    I came up with an idea for to try and improve the efficiency of the BodyFK / Leg IK calculation and still use floating point variables. To me it seems like the most CPU intensive task is calculating all the rotation matrices. In my code I've tried to keep all trig function calls to a bare minimum by calculating rotation matrices to ram. This is very early work and there is opportunity for improvement for sure. With a 96 MHz clock its taking about ~1920 uS (1.9 ms) to calculate the IK for all 6 legs using no lookup tables. I've put my code up on github in case it might benefit the community.

    Here is a youtube vid from the other night executing the code:
    My wire management needs some work

    Last edited by ANTMAN; 06-06-2015 at 12:35 PM.

  9. #259

    Re: PhantomX using a Teensy 3.1

    Welcome ANTMAN,

    You are welcome. Note with the Teensy 3.1s, I have also had good luck running at 120mhz, so if you need some extra speed that is always an option. Will try to take a look later. Also pictures and videos are always great.


  10. #260

    Re: PhantomX using a Teensy 3.1

    Quick update: Yesterday I received my updated smaller Teensy carrier boards back from OSHPARK, that should have the ability to add the enhanced Sound capabilites using the DAC through small built in amp. Also if I did this properly, I can also build the board to just have a simple RC circuit like before, which I may try out with a Teensy LC...

    So in the next few days, I will probably take a diversion, of my diversions of my previous diversion and assemble one of these to see if it works... Maybe two if I get inspired and want to try out LC...


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