Screen Saver

Guy Dupont's USB touchscreen adapter hack saved him from having to spend $150 for a driver to use a device that he already owned.

Nick Bild
21 days agoDisplays
$150 to use my own display? No thanks! (📷: Guy Dupont)

There are some very heated debates on the topic of consumers’ rights to repair, reverse engineer, and modify the electronic devices they own. Advocates argue that these rights are essential to innovation, promoting sustainability, and empowering consumers to have control over their possessions. They contend that restrictive policies, such as those implemented by certain manufacturers that limit repairability and access to parts, hinder competition and lead to unnecessary electronic waste. Conversely, opponents, typically represented by some manufacturers and industry groups, raise concerns about safety, security, and intellectual property rights. They argue that allowing consumers to tamper with devices could compromise functionality, pose safety risks, and potentially infringe upon patents and copyrights.

The examples demonstrating why consumers should have a right to tinker with their own gadgets are numerous. One particularly blatant example of consumers being fleeced to use their own devices was recently highlighted by hardware hacker extraordinaire Guy Dupont. After purchasing an inexpensive touchscreen display, Dupont found that if you actually want to use it with a Mac, you will need to purchase a driver that costs $150 for each machine that you want to use it with.

That did not sound at all reasonable, so Dupont decided to build his own USB converter that could map touch events on the display to standard mouse and keyboard events that any computer could understand. And as it turned out, it was not all that difficult of a job — hardly worthy of a $150 driver.

After plugging the display into a Human Interface Device (HID) interceptor that was built by Dupont for a previous project, it was quickly determined that the screen reported itself as an HID device. The format that the data was being reported in was also immediately apparent — X and Y coordinates for up to five fingers.

With that knowledge, an Adafruit Feather RP2040 with USB Type A Host development board was used in conjunction with TinyUSB to emulate a mouse and keyboard. This setup allowed the inputs from the touchscreen to be read and converted into a simulated mouse and keyboard that can work with Dupont's Mac, or any other computer. An absolute positioning USB HID mouse library was also utilized such that a touch anywhere on the screen would correctly position the mouse on the host computer. Typically, mouse drivers move the cursor relative to its present position.

Not only did this setup save Dupont over $130, but it also has the advantage of not requiring that any drivers or other software be installed on the host computer. As far as that machine is concerned, it is working with nothing more than a standard mouse and keyboard.

This may be a simple hack, but it demonstrates how important it is for consumers to be able to reverse engineer and modify the devices that they own. A simple hack and a couple spare parts could save you some cash.

Nick Bild
R&D, creativity, and building the next big thing you never knew you wanted are my specialties.
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