The STM32F103 Audio Test Board

Allow me to introduce my DIY ARM based Audio Test Board. On the following pages you'll find a description of the board, how I came to it, what tools I used and in the end, all available downloads.

The idea for this board came to me a little over two years ago. I was working on my DIY guitar amp, and I was having trouble getting the right levels out of the guitar, into the preamp, the level of distortion, etc. Basically, the preamp was a big question mark on the design of the amp.

Brothers in ARMs

Then it came to me, just like Doc Brown when he fell off he toilet and invented the flux capacitor! What if I replace the preamp with a DSP?! I could do EQ and some distortion and change it on the fly (or with a few lines of code) if I wasn't satisfied. I had also read a book called "Digital Audio Effects" by Zölzer where some examples of overdrive and tube simulation algorithms where shown.

However, a DSP was not meant to be. I work home with Linux, and use Windows only if I have to do my tax returns. Development tools for TI or ADC on Linux were not well known to me at the time. What if I used a microcontroller instead? I had an Atmel lying around on a dev board, 66 MHz or so I think, but adding hardware to it would prove too complicated. Finally, after a conversation with a work mate, he recommended an ARM processor from STM to me, they ran at 72 MHz, and gave me an USB dev board from Olimex, since he didn't have the time to play around with it.

After a bit of fiddling on the dev board for some time, adding ADC's, DAC's and a serial interface, I decided it was time to build my own audio processing board.

Speakers: AFC Mk I

Last year (2011)I decided I'd build a pair of speakers. Last time I'd built a pair of speakers, it was 1999 during the students protests and strike in Valparaiso. I got a pair of tweeters and a pair of woofers, two capacitors, an 8 Ohm potentiometer and made a box around them. Ah, yes, I drilled a hole in the front. Sadly/luckily, there are no pictures of those monsters, but they kept me company until around 2005 when I moved to Germany.

This time, I'd do it right. I decided to build a "Picolino 2" from the german "Hobby Hifi" magazine, to replace the E 90 Northridge from JBL, which I never liked to be very honest. I'd have to give it a try.

Wireless and Lenovo S12 (Linux Mint 12)

I had some trouble getting the wireless interface to work. After following several instructions, as well as the out-of-the-box installation, this is what did the trick for me.
This solution is hardware specific, it worked on a Lenovo S12 using Linux Mint 12.