High quality audio recording with MCU

Thread Starter

Just Bucket

Joined Jul 22, 2017
3
Hi everyone. I am something like a musician, but I also like to experiment with electronics a lot.

I own a BOSS looper pedal, but it kinda doesn't fit my needs as well as I firstly thought. Recent days I was thinking abou whether is possible to somehow utilize some sort of MCU or just some ARM solution, doesn't really matter, that would be able to real-time record a high quality audio (16bit depth, <40KHz sample rate, mono, ideally up to 16 seconds) and then playing it back instantly at the same speed. My idea is to have like 8 of those modules and record separate loops that would be triggered at some point by the sequencer.

My idea is to have some processor with sufficient frequency to record the audio and store it in it's RAM and then just burst it out, either with it's own or some external DAC.

So my final question is: Do you think this is even possible or Am I just too silly thinking that I can do this thing more cheapely than BOSS for example with their giant loop pedals that will cost you both of your kidneys?
Thank you for any kind of response, if somebody has any experience with what I'm trying to do, just let me know, I will appreciate any materials provided.
 

BobTPH

Joined Jun 5, 2013
2,587
16 seconds of audio at 16 bits and 44KHz is 1.4 MB of memory, far more than microcontrollers have. You would need at least a Raspberry Pi type board to do this.

Bob
 

Thread Starter

Just Bucket

Joined Jul 22, 2017
3
The problem with RPi is it's latency because the code would run at two existing software layers, but I guess I don't have a choice, since 1.4M is quite a lot for something like a MCU
 

peterdeco

Joined Oct 8, 2019
250
I read on a forum somewhere that this was done using an SD card. Sounds a bit complicated to me but if you can sacrifice CD quality and still have usable music, you can do it with an ISD chip. We use both a standalone ISD1620 for 20 seconds of single music play and an ISD4003-05 for 5 minutes of storage addressable by a microcontroller.
 
Just a thought... some PICs like 18f87j50 have built in external memory busses to connect to external parallel RAM. Maxim's MAX135 is a parallel interface ADC (15 bit). Analog Device's CAC8562 is a parallel interface 12 bit DAC. I'm not saying those are ideal parts, but the concept is easily doable. A couple extra logic gates could be used to select whether you're accessing the external RAM, ADC, or DAC.

I did create an eight bit logic recorder at one time using a 44 pin device to interface with some RAM. It didn't have the built in external memory capabilities and so everything was done by program. It wasn't an ideal setup, but I was still able to capture in the neighborhood of 250kHz. The limiting factor was how fast I could run the program and still have a couple instruction cycles here and there to spare for other things.
 
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MrChips

Joined Oct 2, 2009
22,096
The nice thing about STM32 MCUs is you can run the ADC and DAC entirely from hardware. The MCU processor is available 100% of the time. That is not to say that other manufacturers' MCUs are not capable of doing this as well.
 
I've never looked in to the STM32 before, but after a quick look I have to say it beats my idea. It looks like overkill as far as pins and overall capabilities, but will cost about the same in the end, be more capable, and not have all the design and build time along with other headaches involved. I think I found a new rabbit hole... thanks
 

Thread Starter

Just Bucket

Joined Jul 22, 2017
3
Please describe what function you want.
The only thing I want is to have (for simplicity) two buttons. I press one, it records about 16 seconds of audio and when it finishes and I press the second button, it spits all the audio back, every time I press the button. Those functions would really fit my needs
 
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