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  1. W

    Prop Shield Beta Test

    Cool. I didn't even know this was in the works. I don't have a lot of time to do much beta testing, but I'll be really excited to play around with one when it comes. Thanks!
  2. W

    Need help with FTM settings

    Ok, I think I got it. The ISR code you have doesn't clear the interrupt flag, so the interrupt code get's called over and over again in an infinite loop. If you've only enabled the timer overflow interrupt, you'll want the first line in the ISR to clear the flag by writing a 0 to the TOF bit...
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    Need help with FTM settings

    In your last set of code, it looks like you're leaving the clock source selection of the "FTM0_SC" register 0s (this is bits 3 and 4), which effectively disables the FTM counter. I'd guess that the ISR is effectively getting called again as soon as it completes. I'd also suggest that you do...
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    Using an I2S microphone with Audio library and no audio shield... Wiring help

    Check out my fork of the audio library:https://github.com/whollender/Audio I added a couple objects to work with a 24 bit codec. The code assumes that the teensy is the I2S slave, but it should be a good starting point for you.
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    Audio Library

    Hi Anthony, I don't know where USB audio is on Paul's list, but I'm looking into furthering the work done by MickMad to try to get USB audio working with my SuperAudioBoard project (see the forum thread or the hackaday project page). I've got MickMad's changes integrated into the current...
  6. W

    Hackaday Superconference Audio Workshop

    Cool, glad your proposal got accepted. I hope to make it down to attend, should be fun.
  7. W

    Overclocking to 96Mhz Question

    The max multiplication factor of the pll is 55, so you could theoretically go all the way to 220MHz with a 4MHz input clock. Looking at the data sheet, the quoted max output frequency of the pll is 100MHz, so I'd guess that the frequencies Paul mentioned earlier as being close to unstable are...
  8. W

    Overvoltage protection when interfacing an op amp to analog input

    The reason that the zener needs to be at the junction of the two resistors is because the zener only regulates the voltage across its terminals, so the input of R3 will not go above 3.3V. In the original diagram, the input of R3 is tied directly to the output of the opamp, so it will always...
  9. W

    KISS FTT Library Port

    The FFT itself doesn't care what the sample rate is, you just have to be careful how you interpret the output. For a 44kHz sample rate, the max frequency component (the last bin) is at Fs/2 = 22kHz. If you change the sample rate to anything else, the last bin will always have a frequency...
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    Audio Library

    Yeah, I've been trying to think of a good way to go about redefining the sample rate so that it can be selected by the user but still maintain the benefits of a defined constant. Maybe something similar to how the cpu frequency is selected? Or, maybe enclose the definition in AudioStream in...
  11. W

    Audio Library

    The crystal on the board is a 24.576MHz crystal, and the i2s isolators are unidirectional, so I had to either go with master or slave mode and chose master mode for best performance. If the crystal was 22.5792MHz instead, then it would do 44.1kHz. Edit: it looks like Digikey has one crystal...
  12. W

    Audio Library

    @mlu, Sorry, I thought of making a new thread, but this one seems to be the most official one for Audio lib stuff. I agree that it is easier to have multiple threads, so I'll make a new one next time. @Paul, I'm not quite sure that it's ready for primetime just yet. Here are a couple of...
  13. W

    Audio Library

    It's working! Turns out I hadn't correctly adjusted the DMA major loop iteration count for the 32 bit transfers, so the DMA would overwrite its buffers. I haven't tested all the other functionality (volume, dither, etc), but that should be pretty easy to test.
  14. W

    Audio Library

    Hey Charley, Thanks for taking a look and the suggestions. I have a working setup outside of the audio library and have been using that as a reference. The codec setup I can verify as exactly the same as in the working setup (left justified, etc), and I'm using nearly identical I2S setup...
  15. W

    Audio Library

    I'm trying to get some new I2S library objects working for my 24 bit audio board, but I'm having a lot of trouble. I'm trying to set up the new I2S objects such that the I2S and DMA transfers are all 32 bits (with the upper 24 bits containing signal), and copying only the 16 most significant...
  16. W

    AudioAnalyzeFFT1024.available() returns false

    I can't say for sure without the code for both libraries in front of me, but I'd guess that the ADC library constructor is changing the settings for both ADC0 and ADC1, which is interfering with the correct operation of the audio library ADC code. I just took a look at the ADC library code, and...
  17. W

    24 bit audio boards

    I do want to sell populated boards at some point. The up front costs of getting a manufacturing run together are pretty high (especially for this board), so I was investigating a kickstarter or similar crowdfunding type deal for people that were interested. As far as a timing goes, right now...
  18. W

    24 bit audio boards

    The actual capacitors need to be slightly less than double the crystal's spec'd load capacitance (ideally 40pF, but we use 39pF to take into account the board's parasitic capacitance). You can use any crystal in the same footprint that has a 20pF load capacitance.
  19. W

    24 bit audio boards

    Octopart has a nice feature that looks at major distributors and lists the available stock and prices at different quantities (link). Looks like avnet, digikey, and mouser all have stock in the US. RS seems to be the only place in Europe that stocks for small quantities: (link).
  20. W

    24 bit audio boards

    @WMXZ, that's pretty much what I had in mind to allow the codec to work with the rest of the audio library. I haven't thought to much about the actual implementation, but I think I'd have to extend the existing I2S objects to do full 32 bit transfers and the truncation back to 16 bits before...
  21. W

    24 bit audio boards

    Paul, Have you had a chance to take a look at the board yet? I just got the board working with Raspberry Pi (Hackaday project log). My next task was going to be setting up an audio lib object with the codec set up in 16 bit mode so that it would work with the audio library as is.
  22. W

    24 bit audio boards

    That's great! I'm excited to have someone else take a look at it.
  23. W

    24 bit audio boards

    Hi Robin, The FB parts are all surface mount ferrite beads. There should only be two different parts for these reference designators (I think there are two 0805 parts, and 6 0603s). All the 'Conn' parts, and the battery are all 0.1" pitch headers.
  24. W

    24 bit audio boards

    According to the datasheet, the last digit is the type of reel (or no reel at all), so you may want to be careful that you don't end up with a reel instead of a just a few parts :)
  25. W

    24 bit audio boards

    I added the code I used for loopback sine wave testing to the github repo: https://github.com/whollender/SuperAudioBoard/tree/master/SineTestCode I don't know how much real documentation I'll be able to get finished in the next few days, but I think (hope :)) that the assembly should be pretty...
  26. W

    24 bit audio boards

    I just wanted to make sure that you guys weren't having any issues getting it put together, because you seem to be the first to try (other than myself, of course :)). I've been meaning to do a bit more documentation, so hopefully I can get something put together by next week. I'll also get...
  27. W

    24 bit audio boards

    It's probably overkill for most people :D Paul, have you made any progress on getting a board built up? I really need to do better documentation, so please let me know if there's anything that is unclear. BTW, I put up a hackaday.io page for this with more of the results in one place, and...
  28. W

    24 bit audio boards

    Chrome wanted to post twice for some reason. See below.
  29. W

    24 bit audio boards

    Hey Paul, sorry I couldn't get back to you earlier. Coilcraft only sells through their website, but you can probably get something equivalent with the same inductance and footprint from digikey. The battery thing is just a two headers. This is the pn I got:SBH341AS-ND
  30. W

    Teensy 3.1 Analog pin/ADC impedance.

    The "Cookbook for SAR ADC Measurements" app note (AN4373) has really good information on the ADC input circuitry and how to drive it to avoid settling issues.
  31. W

    Multiple audio signal processing

    I haven't tested anything, but the reference manual for the MK20DX256 seems to indicated that it can do a 'TDM' type of I2S interface. In the SAI chapter (48), it mentions multiple times that there is a configurable number of words per frame (up to 32). This should allow you to use a single...
  32. W

    Connecting a Speaker to Teensy 3.1 DAC / A14 ?

    I'd be a bit wary of going back to a larger resistor in the voltage divider. The voltage waveform in your last post shows a minimum of 1V and a maximum of 4V, which is pretty much as far as the LM386 can go using a 5V supply. If you do try a larger resistor, you'll probably end up overdriving...
  33. W

    Connecting a Speaker to Teensy 3.1 DAC / A14 ?

    I wouldn't worry about the 220uF capacitor change too much, but the 0.1uF cap may be causing an issue with stability. If you have multiple 0.1uF caps, try putting another one in series with the ten ohm resistor and 0.1uF cap that's already there. Caps in series will combine like resistors in...
  34. W

    Connecting a Speaker to Teensy 3.1 DAC / A14 ?

    Hmm, it still looks like the lm386 output is clipping. I would try replacing the ground side of your resistor divider with a 1k resistor to see if that helps. That should reduce the gain through the divider enough to see if you can get a clean signal out to the speaker. Once you get the gain...
  35. W

    Connecting a Speaker to Teensy 3.1 DAC / A14 ?

    Nantonos, wouldn't the line out level method only change the output level if the audio board was being used? It doesn't seem logical for it to change the DAC output level. KurtE, in the last screenshot, it looks like you have either digital pulses going into the cap and divider, or the DAC is...
  36. W

    Incomprehensible Software Issue With An NRF24L01 Set-Up

    I'm pretty sure that the compiler will completely optimize away an empty if statement, so it won't ever read or compare the variables used in the if statement itself. In your first post you were able to run the code when there was a statement inside the outer if, but nothing in the inner if...
  37. W

    Connecting a Speaker to Teensy 3.1 DAC / A14 ?

    The DAC output may still be overdriving the LM 386. Try lowering the DAC volume (I think there is that capability in the audio lib)
  38. W

    Connecting a Speaker to Teensy 3.1 DAC / A14 ?

    It looks like the lm386 wants a ground referenced input. This means that it expects the input to vary around ground. The teensy DAC has outputs that vary around a fixed DC voltage that depends on the voltage reference used. In this case, it looks like the DAC is set up to use the 1.2v...
  39. W

    24 bit audio boards

    I'm really glad they caught it; that would have been a real pain to find and troubleshoot.
  40. W

    24 bit audio boards

    Doh! Sorry, Paul. One of the few things that I changed was an update to those pads to make the positive side of the output caps square instead of round to make the polarity clearer, but I must not have re-generated the planes afterwards. The files are updated in github and there's a new...
  41. W

    24 bit audio boards

    It's fixed. Thanks for catching that.
  42. W

    24 bit audio boards

    Paul, I'm completely ok with that. Let me know if you have any issues with the files, or if anything is unclear.
  43. W

    24 bit audio boards

    192kHz sample rate works! The mk20 chip doesn't specify it's I2S interface very well, so I wasn't sure if it would work with the isolator ICs slowing the interface down. Here are a couple of frequency response plots: @ 48kHz sample rate: @ 192kHz: @ 192kHz zoomed to show -6dB point (-3dB...
  44. W

    24 bit audio boards

    Thanks, kpc. I finally got around to putting the files up on github, and the project is released on oshpark as well. Edit: updated oshpark link to the fixed version of the board. I did make some changes to the board design that is provided which have not been tested, but the changes are very...
  45. W

    24 bit audio boards

    Hey kpc, That sounds like a pretty interesting application. Here are some more results: Left channel with open inputs: -1dBFS loopback with synchronous fft: -60dBFS loopback with synchronous fft: Isolation test (-1dBFS 1kHz sine wave on left channel, measuring left and right channels on...
  46. W

    24 bit audio boards

    kpc, I had planned on playing around with some averaging to do some spur hunting. I can do synchronous voltage domain averaging on the teensy pretty easily by just summing into a circular buffer (works as long as the buffer length is an integer multiple of the signal period). I might be able...
  47. W

    24 bit audio boards

    I need to make a few tweaks to the silkscreen and decide what license to use (I'm still deciding whether to try selling populated boards, which may have an impact on how I share the design files), but I should have it up soon.
  48. W

    24 bit audio boards

    @kpc, I did screw up the scaling (I was up too late and trying to get the plots off before my laptop battery died). The whole plot should be ~6dB higher (forgot to scale for max sin amplitude of -3dB and also grabbed the positive half spectrum without adding in the negative side for another...
  49. W

    24 bit audio boards

    An update at last! I finally got the rest of the board assembled and was able to do some preliminary testing this evening. Here's picture of the completed board along with my 'loopback cables' :) (taken with my terrible cell phone camera): I have some quick test results as well: Edit: All...
  50. W

    Interleaved PWM signals

    Freescale has plenty of app notes that reference motor control here: http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=K20_72&fpsp=1&tab=Documentation_Tab You may be able to find one that has an example of the settings needed for various dead time settings.
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