Adafruit Holiday Shipping Deadlines 2018: Attention! Please place all UPS Next Day orders by Monday 12/17/2018 11 AM EST
0

USB Keyboard AVR Programmer

04b5ec54ea4691418b44d3b7e64893af.media.800x632

AVR Programmer Built From a USB Keyboard

Recently, my keyboard became louder and louder while typing, so I decided to buy a new one. But what to do with the old one? Ever since I saw the AVR programmer that uses a USB hub, I thought of abusing a USB keyboard for that.

Theory

Most keyboards have at least three indicator LEDs (Num-, Caps- and Scroll-Lock), which can be controlled from the host using a HID Set_Report request, and thus can be used as general purpose outputs. The inputs are a bit more tricky, since the keyboard uses a scan matrix divided in rows and columns. Most keyboards also do some debouncing and detect rows that are ‘stuck’, which means that we need to simulate the keypress of a single key. If a key has been pressed, the keyboard triggers an interrupt transfer with 8 bytes of data, containing the current state of all keys. The first byte reflects the state of the modifier keys (shift, ctrl, alt, etc.) which I’ll be using as inputs. Additionally, the keys can be polled using a Get_Report request to the control endpoint, but the interrupt transfers need to be handled either way, since my keyboard just locked up after the first keypress when I didn’t handle them first.


Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.

Join 9,200+ makers on Adafruit’s Discord channels and be part of the community! http://adafru.it/discord

CircuitPython – Python on Microcontrollers is here!

Have an amazing project to share? Join the SHOW-AND-TELL every Wednesday night at 7:30pm ET on Google+ Hangouts.

Join us every Wednesday night at 8pm ET for Ask an Engineer!

Follow Adafruit on Instagram for top secret new products, behinds the scenes and more https://www.instagram.com/adafruit/


Maker Business — Japanese word working and more in December’s issue of HackSpace magazine!

Wearables — Solder-less magic

Electronics — = != ==.

Biohacking — Finding Bliss with Anandamide

Python for Microcontrollers — sysfs is dead! long live libgpiod! libgpiod for linux & Python running hardware @circuitpython @micropython @ThePSF #Python @Adafruit #Adafruit

Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at AdafruitDaily.com !



No Comments

No comments yet.

Sorry, the comment form is closed at this time.