When the DS2408 talks to a microprocessor, it is acting more as a character
device than a file, so fits a little awkwardly in OWFS's design.
We could send and receive fixed data blocks. Files like up8 for 8 bytes
read/written. The bus would hang if an imcomplete response, so there would
need to ba a sane timeout.
The machinery is there to do this 1 byte at a time (setting strobe, reading
latch on the alarm channel, writing/reading PIO.BYTE but it can't be called
elegant.
Paul Alfille
On 4/21/07, njh <[EMAIL PROTECTED]> wrote:
On Sat, 21 Apr 2007, Paul Alfille wrote:
> The problem isn't technical -- Louis Swart does it (PIC based) in his
LCD
> controller.
>
> Dallas/Maxim restricts 1-wire slaves (their patents, intellectual
property,
> and "quality assurance"), while making bus master design freely
available
> and unrestricted. I think it's a poor business decision, limitting their
> market, mindshare, etc, but they seem to have the right.
I agree, this seems rather stupid (and probably explains the lack of new
products built around it).
> The DS2408 can also talk to a microprocessor a byte at a time, with a
strobe
> line to coordinate data transfer. We'd have to do some additions to OWFS
to
> support that mode, but it's quite doable.
Yes, my friend is prototyping this approach. But it's ugly, uses up 9
port pins, requires the PIC to interrupt to handle data (rather than
reading from shared memory as with the 2404) and requires another layer of
checksumming. The 2404 based approach was very elegant (although allowing
bus mastering would make it the ultimate low cost sensor/actuator
networking interface).
I don't suppose dallas/maxim are amenable to listening to us mere
hobiests...
njh
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