Note: this is preliminary information

The TdPCT 16i/20io-BMD is a software programmable interface that provides contact closure inputs and outputs for use in conjunction with Blackmagic Design (BMD) Videohub video routers and/or ATEM Constellation video switchers.

The input section transmits switching commands to a video router or ATEM switcher following the closure of momentary external contacts, memorizing the order of contact closure by means of a First In Last Out (FILO) stack, so as to subsequently restore the router states in the reverse order of contact closure. It is specifically designed to be used for broadcast camera colour matching & technical control – a feature sometimes referred to as “Touchdown Preview” (when using dedicated contact buttons), while other times “Joystick Preview” or “Joystick Override” (when using the iris control lever contact closure mechanism).

The output section receives the actual status of an ATEM switcher and closes relay contacts in accordance with the video source selection on the PGM and/or PVW bus. It is therefore suitable for situations where a broadcast equipment requires a simple contact closure for its own tally system.

Unlike the Blackmagic Design GPI & Tally interface, both sections can coexist and can operate simultaneously and independently of each other and the output section can be configured to follow a combination of PGM (red) and PVW (green) tallies for where such use is preferred.

Note: the input section always use the Blackmagic Videohub Ethernet Protocol and so – when referring to ATEM switchers – it can only work in conjunction with those ATEM models that have also implemented the Videohub protocol, such as the Constellation series.

In the basic configuration there are 16 inputs provided, while in the full configuration there are 20 inputs and 20 outputs provided. The inputs and outputs are individually software configurable, so they can be organized in any arbitrary order in relation to the video crosspoints.

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Note: this is preliminary information

Highlights

• Two GPI connectors, each DB-25 female type
  • each GPI connector defaults to 1:1 pin to pin compatible with the Blackmagic Design GPI & Tally interface, thus featuring 16 GPI I/O connections in a single unit
  • each GPI connector can be further configured for up 10 I/O connections, thus increasing the overall GPI I/O connections to up to 20
• (input section) True restoration of any sequence of button or joystick presses, all the way back to the router source that was there previously selected from the panel
• (input section) High quality hardware contact debouncers, making it suitable for use with any quality of mechanical switches
• For ATEM switchers that implements also the Videohub protocol, touchdown preview functionality and tally GPI interface for up to 20 I/O connections are thus possible using a single interface
  • regardless if Videohub or ATEM, a hardware Videohub control panel is usually also required for proper camera technical preview workflow (if not mandatory)
• Robust 1U rackmount enclosure with internal power supply and IEC power connector, thus avoiding loose wires and hanging equipments in rack installations, an useful feature especially when used within an O.B. Van, where everything must be compact and fixed as rigidly as possible

Regarding the GPI input mode of operation, for those unaware of or just to recap, I quote here a concise and relevant description from an old manual of a Leitch GPIO interface that could be used for the same purpose:

When a joystick is operated on a given CCU, the contact closure is made and that CCU’s router input is selected. When the joystick is released, the contact closure opens and the router automatically returns to the previously selected input, usually a studio program video.
(ref.: RCP- Series: RCP-GPI64/32p ... Operation/Installation Manual)

Note: Depending on manufacturer, the same camera remote control product category may have different names and abbreviations – eg. remote control panel (RCP), operational control panel (OCP), remote control unit (RCU), etc.

Unlike standard switching within a video router, the peculiarity of this mode of operation requires storing the exact order in which joysticks or switches are pressed and then released, especially since this usually happens in a completely random order.

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Note: this is preliminary information

Features summary

• Input section:
  • Is compatible with the Blackmagic Videohub Ethernet Protocol
    • based on the officialy documented protocol description
  • Any input can be configured to serve any video router output, thus being able to be organized in any arbitrary order
  • Uses a First In Last Out (FILO) stack in order to restore any random order of contact closures
  • All inputs are floating, using bidirectional optical isolators
  • All return inputs share a common rail, which can be configured in such a way that the input contacts can use either an internal floating power source (thus requiring only a simple dry contact closure), or an external power source provided by user (the latter being meant to accommodate a situation where the contact implicitly provides a voltage source by its own)
  • The interface internal circuitry uses high quality hardware debouncers per each input, in order to adapt to any mechanical switch quality
  • Hardware debouncers added delay per input is between 20ms to 60ms from contact closure to command send to the video router; actual delay depends on the mechanical switch contact bouncing
    • overall delay may further increase slightly if the video router actively uses its video reference input for vertical interval synchronous switching
  • Momentary switching only
• Output section:
  • Is compatible with the ATEM Switcher protocol
    • based on the PyATEMMax library
  • Any output can be configured to serve any video input selected at anytime on the switcher PGM (red) and/or PVW (green) buses
    • the combination of the number of contacts allocated for PGM and those for PVW cannot exceed the maximum number of output contacts of the interface
  • All outputs are floating, using mechanical relay contacts
  • All return outputs share a common rail, completely isolated even from the input section
• Overall control logic is driven by a Raspberry Pi microcomputer, running Raspberry OS (i.e. Linux)
• Configuration of credentials and all parameters are protected against unauthorized access based on standard Linux user rights levels
• For now, configuration of credentials and all involved parameters has to be done in terminal mode, either by attaching a monitor with HDMI input and a USB keyboard directly to the unit, or via serial remote session over USB serial connection, or via SSH remote session over network
• An alphanumeric 20×2 LCD display is provided on front panel for a few basic information – like the current IP or MAC address
• Is build in a robust 1U rackmount enclosure, with internal power supply and IEC power connector
• The product falls within the EMC boundaries for a Class A product (= commercial and industrial usage)
• All components and constructive parts are RoHS compliant certified

The TdPCT interface is available in two versions:

• 16i-BMD basic model, input section only, factory equipped for 16 inputs; there are two DB-25 female connectors, 1:1 pin to pin compatible with the input section of the Blackmagic Design GPI & Tally interface connector
• 20io-BMD extended model, factory equipped for maximum 20 inputs and 20 outputs; the two DB-25 female connectors may be intentionally limited to 16 input and/or 16 outputs in order to maintain 1:1 pin to pin compatibility with the Blackmagic Design GPI & Tally interface connector, or can use all 20 inputs and/or 20 outputs by sacrificing 2 + 2 GND pins from each connector by means of an internal jumper block

Provisions are made for the 16i model to be field upgradeable to the 20io version, by installing an upgrade kit.

Product technical datasheet will be shortly available.

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Note: this is preliminary information

The list price of one TdPCT unit will probably be 1340€ for the 16i-BMD model and 1490€ for the 20io-BMD model, whereas the field installable upgrad kit for 16i-BMD model to be around 300€. However, these are only estimated amounts at this time.

Although almost all the technical details of the project are already established, the availability of the product depends on the public interest shown and my financing possibilities.

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Background: the input section of the TdPCT interface presented here can be viewed, broadly speaking, as the successor of the JOyVerride 20i-BMD interface, which is now discontinued.

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