Jinx wrote:

> Roman, do you have any idea what bandwidth your 1-bit system
> will work up to ? And is it possible to replicate your method in
> hardware only, ie without a micro, perhaps using logic to drag
> data from an EPROM for instance ?

Hi Jinx,
I take it you mean frequency response? It depends
on your sample rate, and that generally depends on your
storage size vs sound length etc. For cheap apps you can
get decent speech at 15625 bits/sec (1953 bytes/sec).

Playback is the standard 1bit system into a filter
with equal time per bit. I'm sure you could do it with
eprom and counter to get bytes, and a shift register
to sequence the bits, but it's going to get big and ugly
real quick. :o) Why not use a 12c508 with internal osc to
do the lot, at 4MHz you get 64 instructions per bit
and all you need do is to get one bit from I2C eeprom
and set/clr the output pin. I think it's even easier
with SPI eeprom. By the time you factor board costs etc
the 12c508 is probably cheaper too.

> Has anyone hacked a talking toy to see how they do it ?

Yes, many low end talking products use the standard
1bit into a filter solution. My free BTC software
gives an easy way to encode files into 1bit format
ready for playback. It also provides a new 1.5bit format
that gives MUCH BETTER sound for the same data size,
but requires 2 playback pins.

I can email you the new windows version of the encoder
if you like, but I don't want to put it up on my page
until i've finished tidying the windows help file. :o)
-Roman

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