[sdiy] My first big project

[Neil Johnson]

David Brännvall wrote:
> The largest external memory size for AVRs is 64k right?
>
> if so, then this is a big limitation, hmm lets think about it:
>   128 patterns = 128 * 16 steps * 16 step = 32kb
>   3 songs = 3 * 512 rows * 16 channels = 24kb
>   8 kb for other stuff and furure use and.

Why not do bank-switching?  Since you're only playing one song at a time,
that would be the best thing to bank switch, which would free up 16kB, or
allow each song to use 24kB each.  Better still, give each song a 16kB
bank (makes decoding easier) and have as many as you like.

Song selection is then merely selecting one of many banks.  E.g. suppose
you use a 64kB SRAM for song data, then the top two address bits are your
bank select and would go to a couple of pins on the micro.

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
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