Chris Aquino uses multiple laptops at the same time, and while this apparently works for his him, needing to take his hands off the keyboard to switch between the two does not. However, he also has a pair of interface devices called ‘feet’ that, like most of us, tend to be under-used. Taking a page out of an electric guitarist’s playbook, he designed a footswitch to go between control of one laptop and the other without lifting his fingers from the keyboard.
The similarity to a guitar pedal is, in fact, more than skin deep, as he’s utilizing a 4PDT (4-pole double throw) latching footswitch normally used for that role. Since USB 1.1 and 2.0 standards only use four lines for power, ground, transmit, and receive, this type of switch makes a perfect method for switching between two controlled devices (perhaps it could even be used as a phone input?) in a snap. In reality, only swapping the transmit and receive lines is really necessary, but switching everything seemed like the simplest solution here.
Though the footswitch is fairly straightforward, perfecting its implementation did take some effort. In addition to figuring out a good 3D-printed housing design, Aquino had to improve his soldering technique, and learned more about how USB works during the process. The project write-up includes links for the STL files, as well as a discussion about switch configurations.
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Author: Jeremy S. Cook