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by dragontamer 1029 days ago
Windows HID interface is very flexible IIRC, and even added I2C support to the HID module or something... in Windows 8 or so?

I don't know all the details, but as I understand it, you don't necessarily need a USB License ($5000/year membership fee) to have a microcontroller running USB-HID across Windows.

Though I haven't figured out all the details of how all the mechanics work, its still interesting to work through even the most "toy" example of the USB-HID stack.
2 comments
Findecanor 1029 days ago
Windows will try to use the VendorID/ProductID pair on the device to look up which driver to load, but if there isn't any then a regular USB-HID device will default to using the generic HID driver.

You'd get assigned a VendorID if you have a USB license: That is a USB-IF thing, not a Microsoft thing. Then each licensee gets to assign its own ProductIDs.

There is no authentication in the core USB protocol: A device can declare any VendorID. Major microcontroller board manufacturers such as Sparkfun and PJRC provide specific VendorID/ProductIDs to be used by DIY projects using their boards ... but I've seen some of those being reused by other boards. I have also seen the VendorID 0xf055 used by free open source firmware.

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veyh 1029 days ago
If your project is open source, you can get a PID for free. [1]

I received one for a virtual usb keyboard [2] that I made to work alongside a desktop app. Having a dedicated VID/PID makes detecting the presence of the device easy.

[1] https://pid.codes/

[2] https://github.com/veyh/AutoPTT-sidekick/

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brokenmachine 1028 days ago
Nice project!
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connicpu 1029 days ago
I was very intrigued by that possibility, but it seems like the stack there is inverted from what it sounds like at first glance. It's for supporting HID devices that are connected to an I²C interface on the motherboard chipset without having to write any kernel-mode drivers. Think stuff like custom lighting or other devices built in to your system that don't need the speed to take up a whole USB endpoint.

I think if someone wanted to have a very simple interface to control I²C devices over USB, it looks like there's plenty of cheap chips around that expose an I²C bus as a simple USB serial port to your computer.

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