The Story Behind the BridgeDuo: Discover how EMP Designs developed the BridgeDuo, overcoming complex power management and USB challenges to create a dual-universe wireless DMX transmitter.

Some products begin with a specification sheet.

Others begin with a challenge.

The BridgeDuo firmly falls into the second category.

While EMP Designs had already developed wireless DMX transmitters in the past, the Bridge Duo was created in response to a very specific industry need: providing reliable dual-universe wireless DMX directly from modern lighting applications running on iPads and other mobile devices.

At first glance, that might sound relatively straightforward.

In reality, it became one of the most technically challenging products we have developed.

A Changing Way of Working

Over the last few years, lighting control applications for tablets and mobile devices have become increasingly powerful.

What was once the domain of large lighting consoles can now be achieved using an iPad running sophisticated control software. For film productions, theatre installations, and temporary event setups, this brings enormous advantages in portability and flexibility.

As these workflows became more common, we were approached by clients looking for a wireless DMX solution that could work seamlessly with an iPad while supporting two full universes of CRMX transmission.

The request sounded simple enough.

Develop a compact device that could connect directly to an iPad, transmit two wireless DMX universes, and be practical for use on professional productions.

As we soon discovered, the challenge was not the wireless transmission.

The challenge was power.

More Than Just Two Transmitters

From a wireless perspective, operating two transmitters within a single enclosure was relatively familiar territory.

Multiple radio systems require careful frequency management to prevent interference between channels, but this was something we had successfully addressed in previous products.

The real challenge emerged when we began looking at how the device would be powered.

The original concept relied on power being supplied directly from the connected iPad.

While this worked, there was an obvious downside.

Running two wireless transmitters while simultaneously communicating with lighting software places a significant load on the tablet's battery. Users understandably wanted longer operating times without constantly worrying about charging their device.

Existing solutions on the market often addressed this problem with external "Y-cables" that allowed power to be injected into the tablet while maintaining the USB connection.

Technically, it worked.

Practically, it felt clumsy.

We wanted something better.

Creating Seamless Pass-Through Charging

Our goal was to allow users to connect an external battery directly to the BridgeDuo, with power passing through the unit and charging the connected iPad.

In theory, this sounds straightforward.

In practice, modern USB power negotiation is anything but simple.

Whenever power is connected or removed, a series of communications take place between devices to determine who is supplying power, who is consuming power, and how much power is available.

The complication was that different iPad models behaved differently.

Some devices negotiated power in one way, while others introduced delays or variations in how they handled power handovers. Behaviour that appeared consistent on one device could be completely different on another.

The situation became even more complicated when external power was removed.

At that point, the BridgeDuo needed to stop supplying power to the iPad and instead begin receiving power from it — all without interrupting operation.

To the user, this transition needed to appear seamless.

To the engineers developing the product, it became one of the most difficult aspects of the entire project.

Solving the Power Switchover Problem

A significant amount of development time was spent evaluating different power-management architectures, processors, USB controllers, and charging chipsets.

The fundamental problem was maintaining power to the BridgeDuo during the brief period when the iPad and the device negotiated the transfer of power responsibilities.

The switchover time varied between devices.

Some responded quickly.

Others took considerably longer.

To overcome this, we developed a system capable of maintaining operation throughout the transition period, effectively bridging the gap while the iPad and BridgeDuo renegotiated power delivery.

The result is a device that can intelligently manage charging and power delivery without requiring users to think about what is happening behind the scenes.

Connect external power and the iPad charges.

Remove external power and the BridgeDuo seamlessly transitions back to being powered by the iPad.

No additional cables.

No rebooting.

No interruption to wireless transmission.

Just a system that quietly takes care of the complexity for you.

Beyond Wireless DMX

As development progressed, BridgeDuo evolved into much more than simply a wireless transmitter.

We wanted users to be able to configure the device quickly and easily without needing dedicated software.

To achieve this, we developed an integrated web interface that allows users to configure both wireless universes, select communication protocols, and manage network settings directly from a browser.

This provides a flexible setup environment while maintaining the simplicity required for on-set operation.

Rapid Prototyping In-House

One of the advantages of developing products entirely in-house is speed.

Throughout the BridgeDuo project, numerous PCB revisions were produced as we evaluated different layouts, processors, USB chipsets, and power-management solutions.

Because EMP Designs manufactures its own prototype PCBs, each new iteration could be assembled and tested rapidly without waiting for lengthy external production cycles.

This allowed the engineering team to maintain momentum and continuously refine the design until the final solution was achieved.

Designed Around the User

Interestingly, the physical design of the BridgeDuo was originally influenced by a slightly different vision.

The intention was for the unit to mount directly to the rear of an iPhone using Apple's MagSafe magnetic attachment system.

Although access to certain Apple communication protocols ultimately prevented that specific approach from being fully realised, the magnetic mounting concept remained.

Today, the BridgeDuo incorporates magnetic mounting, allowing it to attach neatly to compatible devices while maintaining a compact footprint.

The enclosure itself was custom-designed and manufactured using 3D-printed, sintered nylon, allowing us to produce robust housings while retaining flexibility during the early stages of production.

A rear membrane interface provides simple access to key functions, including transmitter synchronisation and status monitoring, while LEDs provide clear indication of power and data activity.

The Result: BridgeDuo

What began as a request for a dual-universe wireless DMX transmitter became a much deeper engineering project involving power negotiation, USB communication, battery management, wireless transmission, embedded networking, and industrial design.

The final BridgeDuo delivers two universes of wireless DMX in an incredibly compact package while solving one of the most frustrating challenges associated with mobile lighting control: keeping your device powered without compromising reliability.

As with many EMP Designs products, the technology hidden inside is often far more complex than the simple user experience it creates.

And that's exactly how we like it.