Sony BRC-300
23 October 2008, 08:36 by Chad Reynoldson
The Sony BRC-300 uses a daisy-chained Visca In/Out wiring topology. Generally with AMX, it is required to use a single 232 cable to each unit and we abandon the daisy-chaining.
Last week, I was on a jobsite with 2 of these cameras and they were already wired with the Visca daisy-chain in place and it was impossible to add another dedicated run to the second camera. So I tackled it with some limited success.
First off, on the bottom of the unit is a dip-switch bank to assign the Visca address. The valid assignments are 1-7. This took longer to discover than I’d like to admit, so I add it here first.
Next, the pin-out of the In/Out terminals are identical (Tx on pin 3, Rx on pin 5). So on the Visca Out, we had to swap the Tx/Rx that went to the next unit. We also wired the DTR pin to the DSR pin (1-2) on the Visca In of each unit. The cable is pretty straight-forward, but the mini-din soldering on an 8’ ladder can be tedious work.
What I wasn’t aware of with this daisy-chaining example (amx-cam1-cam2) was that we actually needed the return Visca Out back (amxOut-cam1-cam2-amxIn). Everything worked fine without it (pan/tilt/zoom/focus/onboard presets 1-6). However, I could not get positional information back from cam2 (it worked fine with positional data back from cam1).
That was a bummer because I had written a bunch of code to provide additional presets stored within amx for pan/tilt/zoom position. I also had implemented a nice routine to automatically set the pan/tilt speed based upon the zoom position, so that with tight zooms the pan/tilt speed slowed down and vice versa.
For the record, the EVI-D30, EVI-D70, and EVI-D100 all seem to share the same protocol and it is similar to the BRC-300. However, the BRC-300 uses a 5 byte pan position (the others used a 4 byte pan position) so polling for pan position will be different among the models.
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