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Thread: Dual channel 16bit dac PT8211

  1. #126
    I am having trouble getting hold of this chip reliably. It seems perfect for my use though - package, functionality, size, price. Any similar alternatives that someone can recommend please?

    Thanks

  2. #127
    Senior Member+ Theremingenieur's Avatar
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    I read somewhere that this chip is becoming obsolete soon (or is already) and should not be used for new developments.

  3. #128
    Senior Member bmillier's Avatar
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    I have not found any other audio DACs in SOIC8 and DIP8 that are cheap, run on 3.3V, work with PJRC audio library and are still available- if those are the features you are looking for.
    I bought a batch of 10 from a Chinese vendor on eBay a few months back for about $5 as I recall. I only needed 1 at the time, and it worked fine when I wired it up. That was before I found out the Paul at PJRC sells them in a kit with PCB and a few passive parts for about $5. I would have gone that route had I known. Unless you need large quantities, PJRC is the way to go.

  4. #129
    Quote Originally Posted by alialiali View Post
    I am having trouble getting hold of this chip reliably.
    Try eBay: "35 results for PT8211"

  5. #130
    Senior Member+ defragster's Avatar
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    https://www.pjrc.com/store/pt8211_kit.html :: looks like $2.65 for chip with PCB and connection parts

  6. #131
    Thanks, I ordered the chip from ebay/china. My worry is that it won't be available in 1000s. But if I ever sell 1000 units, I guess I'll be happy to have that problem. Since my device is primarily MIDI, and the audio output is just on board for monitoring when not connected to a real synth, I guess I can fall back to the built-in DAC.

  7. #132
    Senior Member PaulStoffregen's Avatar
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    The chip is so cheap, you could probably just buy 1000 of them anytime. Just store in a sealed bag, maybe with a desiccant pack to keep any moisture from causing long-term storage issues.

  8. #133
    Can i use the PT8211 with the DC object of the Audio library to output DC voltage/LFO signals?

    Thanks in advance!

  9. #134
    Senior Member+ Theremingenieur's Avatar
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    Quote Originally Posted by manatee View Post
    Can i use the PT8211 with the DC object of the Audio library to output DC voltage/LFO signals?

    Thanks in advance!
    I fear that you'd have to try it out. Some DACs have an internal digital FIR filter which blocks DC. Even if not, you'd have to check out the useful (linear) DC range which can be obtained. IMNSHFO, a "normal" I2C or SPI DAC, which can be much slower since no full audio bandwidth (22kHz) is required for LFO applications, will make things simpler for you.

  10. #135
    Senior Member bmillier's Avatar
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    @ manatee. I use the PT8211 in some audio projects, but I haven't had time to re-program the Teensy to try DC out to be sure. However, I am sure they will work fine for LFO use. Looking at the PT8211 data sheet, they are an R-2R ladder DAC. So, there is no reason to use an FIR filter with that type of DAC, and none shows up in the datasheet. So DC should be fine.
    https://www.futurlec.com/Datasheet/Others/PT8211.pdf

    My recollection of measuring them in my project is that the DAC output is at Vcc/2 when they are fed a signed 16-bit value of zero. I believe the full-scale output signal is 1 volt peak to peak, centered on that Vcc/2 volt level, or 1.15 to 2.15 volts (@vcc = 3.3V)
    If you want the DC signal to use in an analog synth which uses 1V/octave for the note frequency control, then I think that the PT8211 might not be a good choice as you will have to offset it and amplify it to meet that standard. Since the PT8211's output voltage will vary with Vcc changes, your note accuracy might not be good enough. For that purpose, a conventional, i.e. not an "audio" DAC, would be better. For good note accuracy, I think a 16-bit SPI DAC might be needed, but you might get by with a 12-bit one, in which case Microchip makes some cheap ones.

  11. #136
    Thank you for the in put, really good information!
    I would use it for non-1v/oct modulations, events like LFOs, ADSRs, random voltages and such. I'm comfortable with the analog side, scaling the voltages should be fairly easy, a couple of opamps will do it. My main problem has allways been programming
    That's why i like the teensy audio library, makes it all so fun and easy.

    I was hoping to use this dacs because they are so cheap compared with other 16bit dacs that are around. I already ordered some to try it out, we'll see how it goes.

  12. #137
    Senior Member bmillier's Avatar
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    @manatee. Thanks. For those uses I think you’ll be fine. I bought 10 of the PT8211 from China for just a few dollars- before I realized i could get the little PT8211 board from Paul at PJRC.

  13. #138
    it's working fine with the DC object on teensy 3.2, Thanks for the help and in put!

    Now I'm trying to make it work on teensy 4 with no luck... :\
    based on in information on this topic https://forum.pjrc.com/threads/58197-PT8211-Teensy4 i swapped the following pins without any success:
    9 to 21
    22 to 8
    23 to 20

    I'm i missing something? just installed the latest aruino IDE an also the last teensyduino.

  14. #139
    Senior Member bmillier's Avatar
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    @manatee. I know that I've had the PT8211 working with Teensy 4 using the Audio lib's PT8211 output object. I am not at my computer, but try putting the PT8211's Din on Teensy io pin 7, not 8. IO07 is labelled as OUT1A, which I believe is what is needed to drive PT8211's Din pin.
    Cheers

  15. #140
    It's working now, many thanks bmillier!

  16. #141
    Senior Member bmillier's Avatar
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    Good to hear. Its an easy mistake to make, since the SGTL5000 codec on the Teensy Audio shield has its I2S pins labelled incorrectly. i.e. input to the SGTL5000 goes to its TX pin, and data out of the chip goes out from the RX pin. So , Paul made the Teensy audio shield labels to match that odd convention. So, if you look at the diagrams for the interconnect between Teensy and the audio shield, it might seem like the pt8211 should have its Din pin connected to pin 8, as you initially did.
    cheers

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