V-USB – A Firmware-Only USB Driver for Atmel AVR Microcontrollers

https://www.obdev.at/products/vusb/index.html

by colinprince • 5 years ago

117 31 5 years ago

For those curious:

Atmel AVR Microcontrollers are commonly sold as Arduino.

Some chips (not ATMega 328P but ATMega 32U4) have native support for USB. This allows them to be used as USB HID devices: a keyboard and mouse.

Here is someone else's tutorial:

https://codeandlife.com/2012/02/11/v-usb-tutorial-continued-...

And a shameless plug for an app that I wrote that uses an Arduino to turn your laptop into a keyboard & mouse, so you don't have to carry around an external keyboard for your Raspberry Pi.

https://hackaday.com/2015/06/27/keymouserial-solves-your-ras...

In practice I now use CNLohr's EspUSB because it's even smaller. I dug out the old KeyMouSerial code last week to turn a mouse scrollwheel and iPod clickwheel into a rotary encoder.

https://www.youtube.com/watch?v=FPBzOaLbWhM

V-USB can do much more besides: actuators (power switch, DMX), sensors (thermo, hygro), chip programmers, LCD displays... there are 170 projects listed on the Obdev page.

https://www.obdev.at/products/vusb/projects.html

szc• 5 years ago

I highly recommend using Dean Camera's LUFA stack if you are going to use the Atmel AVRs that have on-board USB hardware.

<https://fourwalledcubicle.com/LUFA.php>

sgtnoodle4• 5 years ago

I recently built a force feedback steering wheel from scratch, and used a 32u4 as the MCU. I started the project a few years years ago, but lost interest in favor of picking up 3D printing. It was a lot easier to finish now that I can make arbitrary 3D shapes. I ended up printing an inline 80:1 two stage gear reduction. Thankfully someone in 2020 implemented the HID PID stack for the 32u4. That dropped the firmware work from probably a month to only a few days. The AVR is a bit long in the tooth; I only get a few hundred loops per second while the USB stack is running. It's plenty fast enough for all the haptic effects to feel good, though. It helped to offload the quadrature decoding to a dedicated IC.

Years ago I made a control panel for Kerbal Space Program, and I used a V-USB based MCU to drive two analog voltage meters as fuel gauges. I also had an Arduino Uno in the control panel, but I used up every single IO pin on it doing a button matrix and LEDs. Enumerating the V-USB MCU is touchy, but once it's up it seems reliable enough to gamble Jeb's life with!

aspenmayer• 5 years ago

Do you have any writeups, schematics, parts lists, and/or code you can share? I know folks in the flight sim community who would love to know more!

glassconclusion2• 5 years ago

Is HID PID fully implemented on Windows / Linux (i.e. does it load a generic driver like USB ACM or USB HID mouse / keyboard). I remember that I looked into this, but couldn't find any recent devices that use this.

guerrilla• 5 years ago

Thank you for puting the minimal circuit diagram right there. That was my first question.

Everyone else, make sure you check out the examples. Some of these are neat.

I have a feeling I'm going to have a lot of use for this later.

tzs• 5 years ago

Thank you for puting the minimal circuit diagram right there.

And I thank them for it being a proper schematic.

Far too many projects nowadays just give a drawing that is essentially a picture of how the circuit would be built on a solderless breadboard such as this [1].

[1] https://v6f7u6f8.rocketcdn.me/wp-content/uploads/2017/04/Mix...

arcticbull• 5 years ago

This has been around for a long long time now so it's super mature, and it's very cool! I've used it in the past to make some esoteric keyboard adapter.

You can do a lot with it, but you may run up against a ceiling once you've committed an AVR to V-USB use as the timing requirements even at low bit rates are very strict, and you might want to consider AVRs with built-in USB transceivers if this becomes limiting.

rkagerer• 5 years ago

Me too! It's great. And one of the few samples of this sort of thing that worked right out of the box.

linux_is_nice2• 5 years ago

Only somewhat related, but what are some other cheap(~$1) MCUs for a few-key USB keyboard?

analog31• 5 years ago

I made such a thing using a board called "Teensy LC." I'm a long time user of Teensy boards for prototyping in an R&D environment, and the LC is the cheapest. My interest was just PgUp and PgDn buttons for a foot pedal page turner.

In addition, I programmed an ESP32 board to do the same thing, but as a Bluetooth keyboard. Both the Teensy and ESP32 can be programmed via the Arduino development environment.

Now there's cheap and there's cheap. The stuff I use is cheap in terms of, it won't break the bank for a R&D or hobby project. Then there's cheap in terms of wringing cost out of a commercial product, which I know little to nothing about.

HeyLaughingBoy• 5 years ago

Then there's cheap in terms of wringing cost out of a commercial product

This is a very astute distinction that hobbyists wanting to go from Arduino to production often miss.

I went from the basically cost-unconstrained world of Medical Devices to wearable consumer sensors (e.g., heart rate monitors, etc.) and it was a bit of a shock to see just how much impact cost had. I mean, you know that in a "theoretical" sense, but it's completely different when you are dealing with it on a daily basis.

duskwuff• 5 years ago

1. Any ATmega32U4 development board. Most commonly sold as "Arduino Pro Micro". Developing a keyboard emulator in the Arduino IDE is pretty easy; if you don't want to do that, LUFA is a great little USB stack.

2. Raspberry Pi Pico. Newer, so it's less well documented, but much more powerful.

peterburkimsher3• 5 years ago

Yes, Arduino, Raspberry Pi, and ESP8266 are the best "cheap MCUs" for personal use, quick shipping, good documentation, for a one-off USB keyboard.

For the RPi Pico specifically, the TinyUSB driver is the way to go. This also supports USB host (plugging a keyboard into the Pico), but that didn't support the mouse scrollwheel when I tried.

https://github.com/hathach/tinyusb/blob/master/examples/devi...

If you're interested in larger-scale manufacturing, and are willing to invest more time and effort in once-off R&D to reduce the per-unit cost, then there's a lot more options of other MCUs (e.g. PIC, Cypress, STM32).

https://en.wikipedia.org/wiki/List_of_common_microcontroller...

Mitch Davis gave a great talk at the Embedded Online Conference this year (which my wonderful manager assigned us time to watch during working hours!), where he bridges the gap between hobbyist Arduino development and professional Embedded engineering. (It's closer than you might think)

https://www.youtube.com/watch?v=mI4FDp5crhE

Miro Samek also has a great series of lectures (which I learned about in the same Embedded Online Conference), which then levels up from an Arduino-style "superloop" to an RTOS, Active Object design pattern, and beyond.

https://youtu.be/o3eyz1gEqGU?t=363

Welcome to embedded development, I hope you enjoy creating new gadgets, and don't forget to share your adventures with the community so we can encourage you along!

rraghur• 5 years ago

Slightly tangential, but I recently wanted a mechanical keyboard converter dongle with QMK.. the pro micro was there only viable option due to supported stacks.

tyingq2• 5 years ago

There's a few variations of really cheap 8051 MCUs with USB support. https://hackaday.com/tag/ch554/

le-mark• 5 years ago

Are these ch554 family parts available in bulk? I don’t find them on mouser or Digikey for example.

peterburkimsher3• 5 years ago

Thank you for commenting to ask your question, Hacker News does have many skilled people around from a variety of backgrounds including embedded systems! So your question is related.

The Edit feature is also very useful, and I often go back to add more details, like you added the (~$1) afterwards. In future, please can you write "Edit" when doing that? It appears that duskwuff has been downvoted, because they assumed that "cheap" meant for a personal hobbyist level, not a professional mass-produced level, and now their comment makes less sense because Arduino & RPi are more expensive than $1. Please do continue to use the Edit feature, it's cleaner than writing a new comment! Just please keep in mind how that affects others.

As for me, I use Arduino, RPi, and ESP8266 for personal use, and NXP i.MX RT1050 chips at work, all of which are outside the price range, so there's not much more I can say. I imagine that the chip shortage is raising many prices these days though.

bpye• 5 years ago

I've found the EFM8UB series to be some pretty interesting USB micros.

floatboth• 5 years ago

I wouldn't go any cheaper than stm32f0. Specifically there's STM32F070 for USB.

colechristensen• 5 years ago

Wow, I never would have thought it would be possible to bit bang USB. Did it once for a serial port and that was a big effort in itself

zamadatix• 5 years ago

It's USB 1.1 low speed which is 1.5 mbps making it much more achievable than one might think on this class of hardware.

FounderBurr• 5 years ago

Not to put too fine a point on it, but how can it be “usb 1.1 compliant” while ignoring “communication errors”?

Most of the devils in the usb protocol, the kind people resort to usb analyzers for are usually related to communications error states and transitions in the protocol that aren’t being handled properly.

DarthNebo• 5 years ago

Pretty cool to revive a bunch of old Arduino's as plug n play HID input devices across platforms!

follower• 5 years ago

Many moons ago I "ported" V-USB to the Arduino platform (before any Arduino used an AVR with hardware USB support) & designed a small shield to enable the required hardware side:

* http://web.archive.org/web/20120204231721/http://code.rancid... (via http://web.archive.org/web/20200119053709/http://www.labrado... (No thanks to Google for screwing over Google App Engine early adopters.))

The project even got featured in a chapter in a book: http://web.archive.org/web/20120203210440/http://www.practic...

As I recall it, mine was not the first ever port of V-USB to the Arduino but was IIRC the first released with source & schematic.

Fun times & enabled some fun example projects (e.g. keyboards, "encryption" dongle, dynamic product/vendor ID driver fuzzing) before hardware USB support became more common & affordable.

I highly recommend the write-up of how they achieved the required throughput to make USB work: https://www.obdev.at/articles/implementing-usb-1.1-in-firmwa...

The write-up is the kind of engaging roller-coaster process of discovery narrative that I thoroughly enjoy reading. :)

V-USB – A Firmware-Only USB Driver for Atmel AVR Microcontrollers

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