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Maker Dave Madison has put collectively a “Minimalist USB Host Defend,” designed to reap the benefits of the Teensy 4.0’s built-in capability to behave as a USB Host — creating an add-on that’s “as bodily small as potential.”
“One of many superior options of [the Teensy 4.0] is its built-in USB Host functionality,” Madison explains. “This permits the microcontroller to speak to different USB units corresponding to human interface units (mice, keyboards, joysticks), MIDI controllers, and even different growth boards over USB serial. Whereas some earlier boards such because the Teensy 3.6 had this function, that is the primary Teensy board to incorporate USB host performance in a small format package deal.”
This compact protect makes it straightforward to make use of the Teensy 4.0’s USB Host capabilities. (📷: Dave Madison)
Whereas the performance is built-in, nonetheless, not the entire {hardware} is current — and it isn’t simply the USB Kind-A socket that is lacking: There isn’t any present limiter, that means that hot-plugging a USB gadget might brown-out the Teensy — or draw an excessive amount of energy and overload the upstream USB port.
“To resolve these issues, the design provides a present restrict swap with a smooth begin function,” Madison says. “This slowly ramps up the present for the Teensy’s host port, and permits using a big (100µF) capacitor to deal with smaller surges. The present restrict swap additionally permits units to be ‘scorching plugged,’ that means related and disconnected whereas the microcontroller is operating. As a bonus, the precise IC I used additionally offers some electrostatic discharge (ESD) safety on the USB knowledge pins.”
The compact PCB is designed to imitate the footprint of the Teensy 4.0 board itself, plus the USB Kind-A port required to just accept a USB gadget. There’s additionally a second row of general-purpose enter/output (GPIO) headers, which permits a Teensy-and-shield sandwich to be related to a breadboard, alongside two mounting holes.
The design recordsdata, Gerbers, and BOM have been launched into the general public area. (📷: Dave Madison)
“Related USB units could be interfaced with utilizing the USBHost_t36 library,” Madison writes. “To this point I’ve examined the protect with a Logitech mouse, a MIDI keyboard, and a handful of controllers (PS3, PS4, Xbox 360, Xbox One, and so on.). All carried out nice and with out challenge. The protect has no digital logic and thus no particular configuration is required when programming. It is totally plug and play with any present Teensy 4.0 USB host packages.”
Extra particulars on the challenge can be found on Madison’s Elements Not Included web site, whereas the design recordsdata, Gerbers, and invoice of supplies have been revealed to GitHub beneath the a public-domain license.
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