Monday, February 11, 2008

Arduino and SP0256-AL2 MIDI hardware speech module

one side

the other side

A completely hardware-implemented version of a previous idea. In a way, it is sort of like what they call an 'Arduino Shield' in that it can connect directly to an Arduino board via a set of male headers that attach to the digital i/o pins and ground, and then a separate line for 5V.

The MIDI signal is conditioned and inverted via a 4n25 optoisolator. I also use a 3.57954MHz instead of the value specified in the datasheet (which is 3.12MHz). Mainly because i had a colorburst crystal lying around. Some other values of components for the SP0256 also differ a little bit from other circuits i have seen. I have used a 1n914 instead of a 1n4148 and two 27pF instead of 22pF.

I have also not added the two-pole low pass filter that is normally used to smooth out the PWM digital audio output. I don't really mind the raw sound, and anyway, a lowpass filter can always be added later very easily.


Anonymous said...

Nice, thanks!

machinesdontcare said...

Cool! Can we hear it in action?

vontux said...

Hearing it in action would be great....