Electronics > Beginners

Ran out of DACs - need ideas producing audio output from MCU

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bitman:

--- Quote from: james_s on October 18, 2021, 10:36:15 pm ---Seems a bit silly to use a 555 if you've got a microcontroller. A digital pin on the micro can do pretty much anything a 555 can. On FPGAs I typically use a delta-sigma DAC but I don't know if that's feasible on a microcontroller.

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Yes and no. It would free up the MCU from having to loop/interrupt while updating a screen at 10-20FPS, and instead I would just have an "enable" digital pin that would turn on/off sound.  But yeah, it's a bit simple and not what I really want.

ve7xen:

--- Quote from: bitman on October 19, 2021, 04:46:44 pm ---
--- Quote from: ve7xen on October 18, 2021, 10:49:04 pm ---ESP32 has hardware PWM? I would use that.

HUB75 also seems to be a purely digital device so it likely wouldn't be hard to move it to other pins.

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That's what I'm coming to too - the only drawback is that I would need to customize a "standard library" but that's not a biggie. I'll update here once I've done some testing.  That said, the onboard DACs may not really be an option if they are 8 bit only (according to specs they are).

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8-bit is fine for basic sound effects; at least considerably better than the square wave that you were considering.

I believe the PWM peripheral offers up to 16-bit, but resolution will trade off against PWM frequency (which is typically the peripheral clock / <2^BIT_DEPTH>), and you probably don't have a fast enough clock available to run it at 20KHz. But maybe you can get 12-bit @ ~20KHz (80MHz / 2^12 = 19531) which should give you something like 8KHz of audio bandwidth depending on your filters etc.

If you want 'high fidelity' you will need a dedicated audio DAC. Either of the above options is probably fine for the use case you're describing though.

ledtester:
I've read that the ESP32 supports I2S (with DMA), so maybe you could use that and a I2S amp, e.g.:

https://www.adafruit.com/product/3006

james_s:
Another option if you want something simple and versatile is one of those ICs that can play back digitized sounds. I think some of them will play MP3 or WAV files right off a SD card and they are controllable via a simple interface. Then you can use whatever sounds you want, and update them easily at any time.

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