At my church, we have 4 of these cameras: Marshall CV503
We use them during services to capture shots of the instruments (drums, keys, etc.) and whatever is happening on stage. They are great little action-style cameras, and they have SDI out on them so they are super easy to integrate into our video system.
They have a lot of adjustment options to them via a local joystick-style controller at the camera, but obviously, that’s challenging to use during a service if we needed to adjust the camera’s exposure. The menu is OSD and shows up on the live output. Plus they’re all over the stage and we can’t walk there during the service!
While I wish they were IP-controllable directly, this particular model does not have that option. They do, however, come with RS-485 serial connectors.
So we decided to create a remote shading system using a stream deck running Bitfocus Companion. The Marshall cameras support the VISCA protocol over RS-485. In fact, if you’re a Windows user, Marshall provides free software to control the cameras over RS-485.
We don’t use a lot of Windows computers around here, and that program requires that the computer running their software be the one physically connected to the cameras via serial. Not ideal for us because the cameras are on a stage and our computers typically are not. Marshall also actually makes a nice hardware RCP – but we didn’t want to pay for that.
So we did what you probably already guessed – put in a Raspberry Pi with a USB to RS-485 adapter that we could control remotely.
We have several wallplates across the stage with network tie lines on them that feed back to the rack room in a patchbay. So we made cables that connect to the RS-485 ports at each camera that then go back to a wall plate into a RJ45 port. We utilized the blue/white-blue pair on CAT6 cable. We used that pair because these are data pins in a normal network connection, which means if someone ever accidentally connected it straight to a switch or something, there would not be any unintended voltage hitting the cameras.
Each camera is set to its own camera ID (1-4), and the matching baud rate of 9600 (the default). Then in the rack room, we made a custom loom to take the 4 connections and bring them into a jack, which then feeds into the USB to RS-485 adapter on the Pi.
The Pi is a 4 model with 4GB of ram. Honestly, for what this thing is doing, we probably could have just run it off of a Pi Zero, but I wanted it hardwired to my network, and the bigger Pi’s come with ethernet ports built in.
I bought this adapter off Amazon:
When connected, it represents itself as serial port
/dev/ttyUSB0. We originally planned to use the
socat program in Linux to listen for UDP traffic coming from Companion:
sudo socat -v UDP4-LISTEN:52381 open:/dev/ttyUSB0,raw,nonblock,waitlock=/tmp/s0.locak,echo=1,b9600,crnl
To actually send the UDP data, we’re using the Sony VISCA module already built into Companion. The Marshall cameras use the same protocol over RS-485.
socat method, we quickly found that it would only listen to UDP traffic coming from one instance of the module. We need 4 instances of the Companion module because we have 4 cameras, each with a different camera ID.
However, nothing a small Node.JS program can’t solve. So I wrote a program that opens the specified UDP port, opens the specified serial port, and sends any data received at that UDP port straight to the serial port. You just configure a new instance in Companion for each camera with the same IP of the Pi running the
udp-to-serial program, and the camera ID that you configured at the Marshall camera.
Here’s a video that shows it all in action:
If you want to try this out for yourself, I’ve made the udp-to-serial repository available here: