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    Cool. I didn't even know this was in the works. ...

    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!
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    Ok, I think I got it. The ISR code you have...

    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...
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    In your last set of code, it looks like you're...

    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...
  4. Check out my fork of the audio...

    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...
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    Hi Anthony, I don't know where USB audio is on...

    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...
  6. Cool, glad your proposal got accepted. I hope to...

    Cool, glad your proposal got accepted. I hope to make it down to attend, should be fun.
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    The max multiplication factor of the pll is 55,...

    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...
  8. The reason that the zener needs to be at the...

    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...
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    The FFT itself doesn't care what the sample rate...

    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....
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    Yeah, I've been trying to think of a good way to...

    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...
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    The crystal on the board is a 24.576MHz crystal,...

    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...
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    @mlu, Sorry, I thought of making a new thread,...

    @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...
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    It's working! Turns out I hadn't correctly...

    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...
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    Hey Charley, Thanks for taking a look and the...

    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...
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    I'm trying to get some new I2S library objects...

    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...
  16. I can't say for sure without the code for both...

    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...
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    I do want to sell populated boards at some point....

    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...
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    The actual capacitors need to be slightly less...

    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...
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    Octopart has a nice feature that looks at major...

    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. ...
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    @WMXZ, that's pretty much what I had in mind to...

    @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...
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    Paul, Have you had a chance to take a look at the...

    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...
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    That's great! I'm excited to have someone else...

    That's great!

    I'm excited to have someone else take a look at it.
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    Hi Robin, The FB parts are all surface mount...

    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...
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    According to the datasheet, the last digit is the...

    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 :)
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    I added the code I used for loopback sine wave...

    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...
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    I just wanted to make sure that you guys weren't...

    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...
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    It's probably overkill for most people :D ...

    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...
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    Chrome wanted to post twice for some reason. See...

    Chrome wanted to post twice for some reason. See below.
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    Hey Paul, sorry I couldn't get back to you...

    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.
    ...
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    The "Cookbook for SAR ADC Measurements" app note...

    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.
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    I haven't tested anything, but the reference...

    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...
  32. I'd be a bit wary of going back to a larger...

    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...
  33. I wouldn't worry about the 220uF capacitor change...

    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...
  34. Hmm, it still looks like the lm386 output is...

    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...
  35. Nantonos, wouldn't the line out level method only...

    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...
  36. I'm pretty sure that the compiler will completely...

    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...
  37. The DAC output may still be overdriving the LM...

    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. It looks like the lm386 wants a ground referenced...

    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...
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    I'm really glad they caught it; that would have...

    I'm really glad they caught it; that would have been a real pain to find and troubleshoot.
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    Doh! Sorry, Paul. One of the few things...

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

    It's fixed. Thanks for catching that.
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    Paul, I'm completely ok with that. Let me know...

    Paul, I'm completely ok with that. Let me know if you have any issues with the files, or if anything is unclear.
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    192kHz sample rate works! The mk20 chip doesn't...

    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...
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    Thanks, kpc. I finally got around to putting...

    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...
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    Hey kpc, That sounds like a pretty interesting...

    Hey kpc,

    That sounds like a pretty interesting application. Here are some more results:

    Left channel with open inputs:
    4234

    -1dBFS loopback with synchronous fft:
    4235
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    kpc, I had planned on playing around with some...

    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...
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    I need to make a few tweaks to the silkscreen and...

    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),...
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    @kpc, I did screw up the scaling (I was up too...

    @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...
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    An update at last! I finally got the rest of...

    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'...
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    Freescale has plenty of app notes that reference...

    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...
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