Bootloader Brings USB, Firmware Updating To The ATtiny85

[Jenna] sent in a very cool bootloader she thought people might like. It’s called Micronucleus and it turns the lowly ATtiny 85 into a chip with a USB interface capable of being upgraded via a ‘viral’ uploader program. Micronucleus weighs in at just over 2 kB, making it one of the smallest USB-compatible bootloaders currently available.

The USB support comes from V-USB, a project that puts a virtual USB port on a suite of AVR microcontrollers. With V-USB, it’s easy to turn a Tiny85 into a keyboard, custom joystick, data logger, or computer-attached LED display.

One very interesting feature of Micronucleus is the ‘viral updater’ feature. This feature takes a new piece of firmware, and writes it to a Tiny85, disabling the current bootloader. If you’re designing a project that should have a means of updating the firmware via USB instead of the usual AVR programmer, this might be the bootloader for you.

Not bad for a bootloader that emphasizes small code size. At just over 2 kB, it’s possible to use this bootloader on the similar, smaller, and somewhat cheaper ATtiny45.