[sdiy] Microcontrollers for eurorack use... What to use?

rsdio at audiobanshee.com rsdio at audiobanshee.com
Sun Jan 4 01:41:18 CET 2015


Guy,

There are many choices. You'll want DMA for the audio looper, or specialized sampler chips. I recommend against on-board audio (analog domain), but you certainly want digital audio streaming (SPI or I2S). USB support will probably come in handy.

The XMOS chips have multiple cores, and supposedly allow quick response to multiple inputs (USB, front-panel buttons, CV inputs), but you have to handle most of the peripherals in software using their powerful hardware building blocks (a little like FPGA, but less difficult). They can support digital audio streams for the A/D and D/A, but it's software protocols with hardware support. The USB is fully hardware. XMOS has developer platforms that are geared towards audio, so check out their DJ and audio developer kits. It can be easier to write the separate core programs because each deals with a single input and/or output.

The MSP430 is extremely low power, but easy to program. Not suited for DSP.

I like the TMS320 C5000 series for the combination of low-power, USB support, and very powerful DSP on a single chip.

The PIC and AVR are roughly equivalent in price and capabilities. Their assembly languages are completely different, though. The PIC offers more options to fine-tune the cost of the chip based on feature combinations, but in your quantities that might not matter. The AVR is more popular due to the Arduino.

Your C/C++ experience will come in handy, but I'm almost certain that you'll need to learn some assembly for any chip that you select. That's because the low-power embedded world usually requires a little optimization here and there, especially for interrupt processing, audio signal processing, or anything that's really doing a lot of calculations and/or needs to response quickly.

Brian Willoughby
Sound Consulting


Guy Taylor <geekon at gmail.com> wrote:
> Hi everyone!
> My first post after observing for many years... :)
> 
> I have been making some eurorack modules lately, all analog which has
> been a lot of fun, but now want to try some micro-controller based
> stuff. And there are two levels of cpu power i'm considering.
> 
> Something simple, like for a CV recorder and something more complex,
> like a multi channel audio looper.
> 
> I realize there are many options but what do you guys think would be a
> good starting point for projects like the two above?
> 
> Ideally factoring in:
> Chip types/families, ram, flash etc
> Built in features: audio io?
> Power consumption - the less the better
> Maturity of existing libraries for audio etc
> 
> I have decades experience with c/c++/c#, so the code doesn't worry me
> too much, I really would like to select hardware which is appropriate,
> rather than just guessing (i tried some test with netduino boards but
> there seemed slow and not great for realtime stuff)
> 
> Thanks in advance
> Guy




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