Re: Alternate network and local storage for the Dreamcast

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

lausgans@ wrote:

> David Brownlee <abs <at> absd.org> writes:
> 
> > Just found a very interesting Russian site discussing Dreamshell - a
> > homebrew OS for the Dreamcast.
> > 
> > They have some very nice hardware pages, including schematics for:
> > 
> > - serial to SD adaptor:
> > http://translate.google.com/translate?sl=ru&tl=en&u=http%3A%2F%2Fwww.dc-swat.ru%2Fblog%2Fhardware%2F14.html
> > easily available pre-built (google "dreamcast dreamshell sd") online
The original JJ1ODM page is here (in Japanese):
http://jj1odm.qp.land.to/dcserial_ft232bm.php#sdcard

> I love how simple SD adapter schematics is (well it's always simple
> in case of SD :)

Unfortunately full manual bitbang ops for SPI is too slow for
multi task OSes. On the other hand, NetBSD/evbsh3 has SDMMC driver
using SCIMCI on SH3/SH4:
http://nxr.netbsd.org/xref/src/sys/arch/evbsh3/t_sh7706lan/scimci.c
http://nxr.netbsd.org/xref/src/sys/arch/evbsh3/conf/T_SH7706LAN#96
http://d.hatena.ne.jp/nonakap/20090504/p2
It's also slow (~20kbyte/sec?), but SH SCI serial also supports DMA
so it might be possible to use it as a root fs.

> What wonders me is whether NetBSD has support for this device?
> Or anyone plans to add it soon? Would be great to have r/w rootfs
> on a card.

Just FYI, here is my dumb past trial of SD on SCI (not SCIF) on dreamcast:
http://www.youtube.com/watch?v=v80kyFoSAx8
It's PIO only, still very slow and fragile, write op is very unstable,
though.

> The next thing of interest will be ethernet. Well, as serial port will
> be busy with SD, what will be a best way to attach ethernet? BBA
> adapters aren't the option, as they cost too much.

The above JJ1ODM page also mentioned LAN adapter (mbe(4)) compatibles
and BBA compatible:
http://jj1odm.qp.land.to/g2bus.php#hit0300_clone

---
Izumi Tsutsui