The interrupt-driven audio player is part of ez328monitor. It's a program
for 'ez328 boards that runs without an OS, intended to provide a quick way
to test hardware. You can get the code to that at:
For the sound samples, i had been using mpg123 and sox to convert .mp3
files to raw 32khz 8-bit sound samples.
This uncompressed sound can fill up an 8mb DRAM chip pretty quickly
though. As I was just trying to test the hardware I didn't mess with any
As for the hardware, let me try my hand at ascii graphics :)
PWM (from ez328) |\ 100uf
.______ | \ +| | _
|______>--------| >--------| |-------<*> Headphone connector
| / | | |
Buffer * -----
This method works ok (check the current specs on the buffer! Headphones I
tested use about 20ma) for headphones but for anything more powerful you'd
need an amplifier. The capacitor is probably a good idea either way,
because it strips off the DC part of the signal, reducing current
requirements and improving the sound.
On Thu, 20 Jul 2000, David Beckemeyer wrote:
> A long time ago, you said:
> > I had connected the PWM output (not of a ucSimm but of
> > my Kiwi) to a buffer chip to increase the current. The output from the
> > buffer chip connected through a 100uf capacitor (to remove the DC) to
> > headphones. It plays 32khz audio nicely, and I can fit a good portion of
> > a song in my 8MB DRAM uncompressed.
> Can you provide the circuit example and/or code samples showing
> how you did this? What did you use for source data format?
> - david
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