Design Con 2015

EEvolution of an idea: Innovative inline USB power analyzer

-July 12, 2013

This is a first in a series of stories called “EEvolution of an idea” showing how a good idea got its start and evolved into a viable product in the electronics industry. I would ask our faithful EDN readers to comment on this series idea and if there is a good positive response which views this as something useful and educational to our readers, then I would like to continue with more interesting and innovative stories like this.

I was recently alerted to an innovative new product called the PortPilot in a comment to an article on EDN.

PortPilot Pro is an inline USB power analyzer, designed by J. Loren Passmore. Passmore describes himself as “an entrepreneur who consults with companies in a variety of industries to envision innovative products and speed their path to market.

Passmore grew up tinkering with electronics at an early age like most of us did. He studied physics and engineering at Swarthmore College and after receiving his degree, moved on to hardware and software system development. Working in a variety of engineering and management roles at startups and large companies, Passmore has seen firsthand how having the right tools for the job can be critical for getting a product to market on time.

He initially made the PortPilot Pro because he needed a tool to measure the power a USB device uses, speeding his development a USB product for a client with particularly stringent power requirements.  He describes the device as a simple tester for USB power -- inexpensive yet indispensible given the increasing prevalence of USB power sources.

Passmore says, “These days, a lot of the designs I'm working on are powered from a USB port. Even if the final product isn’t USB powered, the development system probably is. I ended up putting together an inline power meter to make it easier to keep tabs on the design's power consumption during development. It's powered by the USB bus, and measures the USB voltage and current draw as well as the total energy over time, and displays the results on a small screen.

PortPilot Pro in use on the bench, measuring the power consumed by a TI BTLE evaluation board.

In addition to measuring USB current and voltage, it can also identify the various charger types (DCP, Apple 0.5/1/2.1A, and PC) and can present a different charger type on the output port (useful when testing devices that need to charge from different USB ports).”

Finding the device so useful in his work, Passmore launched a crowdfunded project to commercialize the design.

The evolution of the PortPilot design

The original PortPilot prototype (top) and the pre-production version of the PortPilot Pro shows the evolution of the design in both package and features (Image courtesy of Loren Passmore)

Passmore commented, “As you can see, I had initially made a larger unit with three buttons. The input was a USB mini-B connector. By the end of my prototyping, I had concluded that the real utility of this device is in its simplicity -- an inline unit (no extra cables to remember) with no complicated menus (it should tell you what you want to know when you plug it in).”

Here is how Passmore describes the tool:


Passmore told me, “Looking back at the original prototype reminded me of something else that may be interesting about the PortPilot Pro design -- because I initially made PortPilot as an internal tool, I didn't even consider making a custom enclosure, but also couldn't find an off-the-shelf enclosure that would work. I hit on the idea of encasing the unit in clear, heavy duty heat-shrink tubing, and was so pleased with the result that I decided to keep it for the Pro units. I like the fact that it exposes the design to view - PortPilot Pro is an engineering tool, and it somehow seems appropriate to me that you can look at it and see how it works.”

How PortPilot Pro Works

The block diagram below shows the way the PortPilot Pro handles the USB bus. 

Block diagram showing how PortPilot Pro handles the USB power and data signals. The Pro unit can switch the USB power on and off, and switch the USB data lines either straight through or to a charger analyzer (on the input) and charger emulator (on the output)

Because the Pro unit can switch the USB power on and off, and switch the USB data lines either through or to a charger analyzer (on the input) and charger emulator (on the output), the following modes of operation are possible:  

  • With  the output port data lines connected straight through to the input port, the  device can be used to measuring the power used by USB devices in normal operation. (See block diagram photo.)
  • On the output, the data lines can be switched to emulate any charger type (DCP, Apple 500mA/1A/2.1A). This is useful for those developing products that need to charge optimally from various chargers, or for increasing (or decreasing) the amount of current a device will draw from a given source. This is also a useful mode to prevent data transfer to/from a device while still allowing optimal charging.
  • On the input, the data lines can be connected to a circuit that analyzes and identifies the charger type and capacity, measuring the D+ and D- lines to determine if the unit is connected to a computer, or one of the various Apple or Android chargers.
  • When enabled, the Pro unit's configurable current limit will disconnected the output port if the current reaches a preset value, a useful feature for testing new designs.

There's also an auxiliary USB port which can be connected to a computer and used to collect data (current, voltage, total energy) measured by PortPilot Pro, as well as to connect, disconnect, or change the output port's charger emulation, and set the current limit.  Programmatically connecting and disconnecting the output USB port can be useful when developing firmware or drivers instead of manually un/plugging a device to get it to reenumerate.

More details can be found on PortPilot’s page at IndieGoGo, an innovative crowdfunding platform that empowers ideas and allows supporters to easily donate funds, generally receiving the product in return for their contribution. Indiegogo has a belief that “anyone, anywhere who is passionate and works hard should be able to raise money” for a good idea.

Crowdfunding platforms like IndieGoGo and Kickstarter are a particularly good match for hardware projects. Like many crowdfunded projects, PortPilot will be funded at the end of the campaign, a structure that allows entrepreneurs to gauge the interest in their idea before committing to production runs. If there’s not enough interest to reach the entreprenuer’s threshold, the project isn’t funded, and the entrepreneurs can move on to another idea. But if an idea catches on, as it has with PortPilot, the project funds the production runs. 

Crowdfunding is an interactive enterprise, and funders are often rewarded not only by being the first to receive a new product, but also by having some influence on evolution of the final product design. For example, PortPilot supporters weighed in last week on the best choice for the Pro LCD (they chose blue). Crowdfunding has launched some large hardware projects, with many notable successes exceeding $1M in funding.

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