[sdiy] Raspberry Pi 2 Synthesizer Project

[Scott Gravenhorst]

Phillip Harbison <alvitar at xavax.com> wrote:
 >Scott Gravenhorst wrote:
 >> I also have the Cirrus Logic/Element14 sound card (24 bit
 >> stereo up to 192 kHz. Line-in, line-out, S/PDIF and other
 >> features).
 >
 >Is this the card you're using?
 >
 >http://tinyurl.com/Element14CirrusLogic

That's it.

 >I'm currently evaluating I/O cards (shields) for RP, Arduino,
 >and other SBCs. I'm curious to know if you considered other
 >audio cards such as the Wolfson Audio card available on that
 >same site. What are you doing for MIDI? I've found some very
 >inexpensive Arduino MIDI shields, some in kit form.

The Wolfson card has a 26 pin connector and won't fit on the Rpi2. 
However, there are strong similarities in the hardware for both.  For 
MIDI I cobbled up a little 6N138 MIDI current loop to 3.3v logic output 
and connected that to the board's console UART port.  Software can set 
the port for 31250 baud.  I'm very happy with the audio quality.

 >> So far, using ALSA, I've made an organ type polysynth (32
 >> voices).  Each voice is computed arithmetically as
 >> y=sin(a)+sin(2a). [...]
 >
 >Would you mind sharing your code?

Heh - I may, but this is pretty lame code TBH :) ... literally tossed 
together from hello world stuff.  So the code needs work before I'd want 
it looked at.  For me, the major hurdle was getting code that worked 
properly with ALSA's needs.  The usual Linux code scrounge through 
tutorials with deprecated and otherwise broken source code.  Once I got 
ALSA and thread use under control, it was pretty smooth.

 >
 >> I'm quite impressed by the power of this little thing,
 >> especially for a $35 computer board.
 >
 >I'm currently evaluating SBCs similiar to the RPi including
 >some that have as many as 8 ARM cores. The Cubieboard4 is one
 >such board. In addition to 8 cores it also has 2GB RAM and
 >built-in WiFi. The price is around $100.
 >
 >I look forward to hearing more about your project. Thanks!

Of the things I like about the Raspberry community, very friendly and 
generous group.  I found a lot of good stuff in the fora.  What is 
frustrating, however, is how seldom people come back to the forum to 
post solutions to problems.  I read down thinking "perfect, my question 
too" and it piffles out.  And then I realized that there were often 
multiple threads addressing the same issue and if you're lucky, you 
might find the one with the solution.  So perseverance on fora is a virtue.

-- ScottG