Hi
Yes, you can absolutely use the control lines on a serial port as GPIO's
in Rivendell, this has existed for several years. You can have up to 4
inputs and 2 outputs per port. Inputs can trigger macros. Outputs can
be triggered by macros.
I've used this quite a bit over the years but I think one setup I had
the most fun with was several years back I built a remote control box.
At the time we had a remote location and I needed to have a way to turn
a studio channel "on / off" from that location but I didn't have any
budget to spend on the setup. I did have an old studio turret which had
4 buttons on it, and 2 of the buttons had LED's that could light up. I
set this up as a "remote audio on / remote audio off / next / whatever
we assigned to it" box in the remote location. I had a Rivendell box
that had its serial connected to the buttons for both GPI's and GPO's
controlling the LED's all using the serial control lines. When the
Remote Audio ON (or OFF) button on the box was pressed it triggered a
macro to send a command across the network to another Rivendell box in
the studio which triggered a GPO (also on the serial port) to turn that
channel channel on (or OFF). I was also monitoring the contact closures
on that channel for both ON and OFF status. When the Rivendell box in
the studio saw that channel turn either OFF or ON it would receive a
status on one of its inputs. It would send that status back to the
"remote" Rivendell box and light up the appropriate button's LED to
represent the status of that channel. It worked well - either end could
turn the channel on or off and see the status change, knowing if that
"remote" location was on the air or not. Furthermore there was no
noticeable delay either - pressing on or off from the remote location
and the console in the studio reacted just as quickly as if you were
pressing its buttons. All done with serial ports, some wiring and
buttons, a few low voltage power supplies (I actually used old phone
chargers I had kicking around), a few transistors and such, I can't
recall what else I used but it was all stuff I had on hand. All without
the need of any extra GPIO cards. It also came in at my budget of $0
(that is, unless you count the time I spent putting it all together).
The only real hiccups it had - if one (or both) ends got rebooted it
would lose track of whether the channel was "on" or "off" and leave both
lights in the remote location off. If this happened the fix was easy -
cycle the channel "on" and "off" again and it would be back to normal.
And of course if the network went down, but that's not really an issue
with the software itself. The talent loved it.
Anyways, getting it working is documented in the Wiki:
http://wiki.rivendellaudio.org/index.php/Serial_Port_/_Modem_Control_Lines_as_GPIO
Lorne Tyndale
An interesting discussion came up. Using just the handshaking pins of
the serial port as GPIOs instead of a device like a GPIO board. Is it
possible to configure the port pins themselves? Can I ultimately use a
macro to set/unset or read the DTR, DSR, RTS, and CTS lines?
Thanks for your ideas and thoughts.
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