Blackmagic Forum

I would like to connect a BMD GPI\Tally interface to my Hitachi Camera Control Unit CU-HD500. Any help or suggestions would be greatly appreciated.
The CCU has a 25pin D-sub communications connector.
Pin 17-Tally Common
Pin 18 G Tally in
Pin 19 R tally in
The CCU has the option of voltage or contact. It is currently set to contact.
I am using a ATEM 2me Prod Studio 4k.
Thanks in advance!

The tally outputs on the Blackmagic interface are mechanical relay contact closures to ground (with a maximum of 30V at 1A), so contact is the correct setting on the CCU.

However, there are only 8 outputs so you'll need a second interface if you want tally for more than 8 switcher inputs. You're also limited to program only tally (either for switcher inputs 1-8 or switcher inputs 9-16).

For fully configurable program and preview tally (amongst other things), I'm using Baz Leffler's excellent RMC2ATEM controller.

I made up a simple 8 source program and preview contact closure interface for our Sony CCUs using a couple of cheap as chips relay modules (i.e. like this :-

Hello Greg. The wiring is fairly simple and outlined on the back of the GPI/Tally Interface box. You didn't mention which crosspoint, but for example Input #1, you would wire pin 23 of the Tally box to pin 19 on your controller. Wire any of the ground pins like 11 near pin 19 on the GPI Tally Box to pin 17 or tally common on your box. Your end is configured correctly. The GPI tally interface needs to be configured with a computer using USB2. In the ATEM Manual there is a section called Using Tally with all the steps to make this work. It's really very simple. Hope this helps.

Regards, Gary

Thank you Mike and Gary for the responses. I guess another source of my confusion, and I'm probably overthinking it like always, is the difference between the GPI and Tally sides of the Tally interface. I really do not want to fry my CCU.
My assumption was that the GPI pins were the contact option and the Tally pins were the voltage option.
Looking forward to having tally lights again.

Hello Greg. Good question. Probably none of the pins will fry any circuits but it's always a good idea to be cautious. Grounding is usually the more important thing. So to answer your question. The ATEM only uses the "Tally" portion of the box. The Videohubs can use both "GPI" and "Tally". The "Tally side is relay contact closures inside the box. So all relays have a common side and each one is separately wired to a device that requires a "contact closure" rather than a voltage. They could be used in conjunction with a voltage device but would usually require some circuitry. You can simulate your CCU by simply shorting the two pins together on the CCU end and see the tally light work. That is all the BMD Tally box does. The important thing to know about the BMD Tally box is don't wire it to a high current device like turning on a 110 (or 220) Volt light

Hope this helps.

Regards, Gary

Thank you Gary and Mike. Your advise and information was right on. Working perfectly!

Hello everyone, this post has been quite informative. I also have 4 of the Hitachi CU-HD500 CCUs and I want Tally on them. I don't mind having tally on only 8 inputs as I only have one BMD GPI/Tally interface. I however, noticed that the CCUs have a Tally and a Communications port behind. So I am sort of confused, Do I connect to the 9-pin Tally port or the 26-Pin Communications Port?
Please your answers would be appreciated.