Oops, early send... Trying again, this time writing the full mail!
The LINK adapter has an extra AUX line which can be used as a general
I/O port (somewhat limited though).
Some background, from LinkUSB manual page:
---
The LinkUSBTM supports the standard RJ45 type 1-Wire bus connection
wherein the center two contacts of the RJ connector are the data and
ground connections to the 1- Wire bus. However, another pin in the RJ
connector is also brought into play. This line is, by default, driven to
the high impedance state and left un-powered. It can be an output
supplying a low level (0 VDC) or a high level (5 VDC), or it can be an
input sensing a 0- 5VDC logic level. When set to the 5V level by the “d”
command, this line can be used to provide power for DS2409 and DS2406/7
type 1-Wire switches. However, the current available from this output is
limited. The amount of current that the Aux line can provide is limited
to approximately 75 mA. ASCII commands used by the host can cause the
Auxiliary I/O pin to change its behavior as needed.
--
The other Link devices have the same, somewhat different details though,
mainly with regards to power levels.
Microsoft Word - LinkUSB Users Guide V1.3.doc Microsoft Word - LinkUSB
Users Guide V1.3.doc
I've added some code to control this line via owfs, commited in branch
link-aux:
https://sourceforge.net/p/owfs/code/ci/fca93b164f8b5f0fd0f97bb66d0be7081c751384/
It basically adds two new points in the filesystem:
/bus.N/interface/settings/ link/auxin
/bus.N/interface/settings/link/auxout
This is visible for Link devices only. Auxin allows putting the AUX pin
in hi-z mode, and reading the current value. auxout puts the pin in high
or low mode.
Is this a good solution? It isn't really a "setting", but it belongs
under /bus.0/interface.
Also, I didn't put auxin/out on the same node, since sending the "read
aux" command will actually put it in Hi-z mode rather than just read it.
Reading from auxout is not doable right now, it would only be able to
reply the latest written value, which may or may not be correct, so I
skipped support for reading.
Let me know how if you think this fits in with the rest of OWFS, or if
it should be solved differently.
Regards
Johan
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