Page 1 of 1

ACS with freeRTOS on Goldilocks - Arduino (AVR ATmega)

PostPosted: Thu Dec 04, 2014 8:03 pm
by feilipu
I've been testing the Audio Codec Shield against a 12bit MCP4822 DAC on a Goldilocks Analogue prototype.
http://feilipu.me/2014/11/25/goldilocks-analogue-part-5/
http://feilipu.me/2013/05/07/making-waves-open-music-labs-dsp-shield-arduino-freertos/
http://feilipu.me/?s=Goldilocks+Analogue

Image

Comparing the two implementations the ACS is better using the same source material. Obviously, the 24 bit DAC on the ACS could do far better with better material than the 16bit 44.1kHz source that I'm feeding it.

I've been building some digital music implementations using the 8 Bit Algorithmic Symphonies examples.
http://countercomplex.blogspot.com.au/2011/10/algorithmic-symphonies-from-one-line-of.html
The ACS sounds significantly more musical than the MCP4822 on Goldilocks Analogue, probably because of the hardware digital de-emphasis filter. The MCP4822 has very square signal response that generates a lot of high frequency noise, which has to be removed by software digital source filtering.

It is possible to run a quasi-real-time RTOS during use of the ACS, but with an AVR platform (Arduino) there is little time available if 44.1kHz sampling is maintained.

I'll write a full article and link it here soon.
The code is available on Sourceforge.
https://sourceforge.net/projects/avrfreertos/

Re: ACS with freeRTOS on Goldilocks - Arduino (AVR ATmega)

PostPosted: Fri Dec 05, 2014 5:22 am
by guest
good work on this. i had seen your writeup last week.