STM32 Blue Pill as an Hid USB Keyboard | Hacker News Reader

STM32 Blue Pill as an Hid USB Keyboard

instructables.com

45 pointsthealienthing33 comments

The F103 microcontroller on the blue pill is the epicenter of price hiking during the semiconductor shortage. I've seen prices upwards of 35 USD for each chip. It was more expensive to get one of these chip than to get a Raspberry Pi.

I think it is better to use the Nucleo series of evaluation boards from ST now as they have first party support from ST.

I ordered a NUCLEO-G474RE directly from ST yesterday. I could only add one to the cart, whereas I wanted two. When I recently bought two NUCLEO-F334R8 I didn't encounter this.

So apparently there is limited stock, and someone else that wants one can get it despite me. That's fine; I'll go back later and get another. It's great to see at least one damn company thinking this way.

BTW, they're providing free shipping for a limited time!

You can purchase some of their boards via Mouser directly who is the one fulfilling orders on STs behalf.

Jeez, I paid 1/3 of that for my black pills, and they're objectively better in every metric.

Those jumped up in price about the same time. Hell, I saw fly by night operations buying up black pill boards just to pull the SoCs off to sell as sketch second sourced chips.

Don't the Pis still go for 100 a pop or has that finally normalized now?

I just bought a 4G 4B for $75 Canadian. More expensive than before the pandemic, but not outrageous. Of course, once you add a case, PSU, cables, etc, you are over $100 again.

Prices started to fall during the last months, but they're still far from the pre-shortage years. It will be a slow process, and being the Pi produced by a single manufacturer, they could take more time compared to other similar products.

I can buy pill for $3 and nucleo for $50. I guess it depends on location, but for me nucleo is like a luxury item.

Can someone explain what this is actual for? Is this just a tutorial for creating your own DIY USB client device?

One example might be bridging an old dumb keyboard into working as a usb keyboard.

Could it also be used to bridge a BT keyboard to USB for the semi-rare cases where having a wired keyboard is necessary (BIOS access, boot loader, login screen etc.)? I expected this type of product to exist, but couldn't really find a good one after a cursory look.

In principle, yes, but you'd need something additional to act as a Bluetooth host. You'd probably be better off using a part that can do both, like an ESP32.

I don’t know of an off-the-shelf way to implement what you want. There’s a usb-usb converter in QMK which allows you to add QMK features to any keyboard, but QMK does not have Bluetooth support. ZMK is designed for Bluetooth but doesn’t seem to have anything like QMK’s protocol converters (tho I might have looked in the wrong place).

You might be able to DIY it with a Raspberry Pi Pico W, by gluing together the picow_bt_example_hid_host_demo and tinyusb_dev_hid_multiple_interface examples from https://github.com/raspberrypi/pico-examples

Could this be used as a rubber ducky type device? I remember last I researched making a DIY rubber ducky it was quite difficult for some reason.

It's an example using STM32CubeMx dev environment. ST supplies many examples, including this one. However, this walkthru helps beginners navigate some of the complexity in getting it running.

Yes, it looks like it's "just" a tutorial.

As someone who recently started dabbling into MCU programming, I can tell you that a tutorial that shows you all the steps, and has an end result that works and can still be tweaked, is valuable. The DX you may be used to in modern programming is something you can only dream of in the embedded world. Every manufacturer has their own bespoke frameworks, tools, and conventions. The development loop is long: you have to build the thing, flash it to the firmware, reboot the device... You're dealing with raw bytes 99% of the time, so compiler type safety is little help in checking that your program will behave as expected and mistakes are frequent. The global state is huge, and with so little computing/memory resources, you're discouraged from introducing complex abstraction that would help clarify the code or avoid mistakes.

> The DX

Developer Experience.

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.

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.

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.

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/

Nice project!

Blogspam. One of many Bluepill + DIY keyboard articles.

Are howto articles considered spam? I found it useful and wanted to share it as well as save the link so I could find it later. If this post violates some code of etiquette I’ll not do it again.

Blue Pills and Black Pills are popular with the DIY mechanical keyboard crowd as the brains of a keyboard circuit. The Arduino Pro Micro is also popular. I imagine that nowadays people also use the Raspberry Pi RP2040.

The common feature among these boards is that they have relatively full-featured USB client support in hardware. This is different from other hobbyist embedded boards, such as most Arduinos, for example, which have only a USB virtual serial interface via a discrete chip for the purpose of uploading and debugging firmware. So if you can make the board look like a USB keyboard, and it has enough I/O to handle a matrix of keyboard switches, then with the right firmware like QMK, you've got yourself the building blocks of a custom keyboard.

My info is stale as of the start of the pandemic, when I gave up my mechanical-keyboard hobby and pivoted to DSLR-based videoconferencing.

Yeah it’s just a tutorial. I don’t really have any kind of platform for saving links I find useful so figured I’d post it here to save it for myself and maybe someone else would like it. I expected it to be completely ignored.

Do these boards still have that design flaw that prevents them from working right with USB? Especially for programming.

I remember replacing a resistor on one four-ish years ago, so that I could use it in a usb2 port. (worked fine with a usb 1.1. hub)

On that note,, does anyone have some resources on using a phone as a USB keyboard? It would be pretty useful not to have to haul around my bulky keyboard when I'm, say, just working on my server. Requiring root is fine.

Android phones: https://github.com/tejado/android-usb-gadget

I have unfortunately not yet developed any mouse/keyboard app for this. I only use it for https://github.com/tejado/Authorizer

Thanks so much for that, I ended up making my own app using Android USB Gadget and some code I stole from Authorizer.

https://github.com/askiiart/android-usb-keyboard

It's my first app, and it definitely shows, but it works. Though, it's definitely missing a fair number of keys.

I've got one of these from way back and was meaning to do something similar in Rust. Yet another project that I just never got around to.

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