On 2017-08-04 13:51, Noel Chiappa via cctalk wrote:
> From: Paul Koning
>> do industrial SD cards exist?
> If you have a ready-made SD interface, these cards work nicely. If you
> need to build one from scratch it gets tricky, because the interface is
> fairly high speed serial (packet based) signaling, and the
> initialization sequence before you can do any I/O is fairly convoluted.
I'm not clear, reading this, if they use the standard SD-interface?
Yes.
Actually, whatever "standard" you just refer to. But the old 3v3 level,
spi-derivative is very simple to implement. The 4-bit mode takes a
little longer, the full speed 4-bit mode needs a nice layout.
If so, yes, it's non-trivial to interface to (as I previously mentioned, Dave
and I wound up defining a uengine, and writing a uassembler to produce code
for it, after Dave decided trying to do the init with a state machine was too
much pain).
Bit-Bang the setup, then think about DMA.
> It is reasonably well documented in the SD standard, but still, it
> takes a while to get all the code working. BTDT.
Tell _us_ about it! :-) (Of course, that issue we had with noise, and the
wierd latching inputs, made it even more painful...)
Really? Did you wire-wrap this thing?
;-)
Cheers
