Micronucleus is a bootloader designed for AVR ATtiny microcontrollers with a minimal usb interface, cross platform libusb-based program upload tool, and a strong emphasis on bootloader compactness. To the authors knowledge this is, by far, the smallest USB bootloader for AVR ATtiny
The V2.0 release is a complete rewrite of the firmware and offers significant improvements over V1.x:
Due to the many changes, also the upload tool had to be updated. The V2.0 upload tool is backwards compatible to the V1.X tool, though.
The last release of the V1.x can be found here:
The bootloader allows uploading of new firmware via USB. In its usual configuration it is invoked at device reset and will identify to the host computer. If no communication is initiated by the host machine within a given time, the bootloader will time out and enter the user program, if one is present.
For proper timing, the command line tool should to be started on the host computer before the bootloader is invoked.
Windows machines will need to install the libusb drivers found in the /windows_drivers folder. Clean Micronucleus devices without uploaded userprogram will not time out and allow sufficient time for proper driver installation. Linux and OS X do not require custom drivers.
Windows 10: Installing unsigned drivers became more difficult in Windows 10. Please use the Zadig driver installer as provided in the /windows_driver_installer folder.
Please invoke the command line tool with "micronucleus -help" for a list of available options.
The bootloader resides in the same memory as the user program, since the ATtiny series does not support a protected bootloader section. Therefore, special care has to be taken not to overwrite the bootloader if the user program uses the self programming features. The bootloader will patch itself into the reset vector of the user program. No other interrupt vectors are changed.
The latest release version can be found here: https://github.com/micronucleus/micronucleus/releases
Archives with snapshots of the latest binaries of commandline tool and firmware can be accessed here: https://github.com/micronucleus/micronucleus/releases/tag/master-LATEST
Micronucleus can be configured to support all devices of the 'classic' ATtiny series, with the exception of the reduced core ATtiny 4/5/9/10/20/40.
To allow maximum flexibility, micronucleus supports a configuration system. To compile micronucleus with a specific configuration, please invoke the AVR-GCC tool-chain with:
The makefile makes use of the gnu binutils and some unix commands such as 'mv' and 'rm'. If you are using Windows, make sure you have proper binaries installed. For example by using the 'Atmel Studio command prompt' or msys/mingw32.
Currently, the following configurations are included and tested. Please check the subfolders /firmware/configurations/ for details.
|t84_default||ATtiny84A default configuration||1476 bytes|
|t841_default||ATtiny841 default configuration||1522 bytes|
|t45_default||ATtiny45 default configuration||1510 bytes|
|t85_default||ATtiny85 default configuration||1510 bytes|
|t85_aggressive||ATtiny85 smaller size - critical||1358 bytes|
|t88_default||ATtiny88 default configuration||1432 bytes|
|t167_default||ATtiny167 default (uses xtal)||1338 bytes|
|Nanite841||Nanite841 firmware||1546 bytes|
|m328p_extclock||ATMega328p external clock||1490 bytes|
|t4313_default||Attiny 4313 default configuration||1456 bytes|
Please note that the configuration "t85_aggressive" may be instable under certain circumstances. Please revert to "t85_default" if downloading of user programs fails.
Precompiled hex files of the bootloader can be found in /firmware/releases. The files can be directly programmed using AVRDUDE or other programmers. The folder /firmware/upgrade contains hex files that can be used to upgrade devices with existing version of micronucleus with a newer version. These can be uploaded using an older version micronucleus.
You can add your own configuration by adding a new folder to /firmware/configurations/. The folder has to contain a customized "Makefile.inc" and "bootloaderconfig.h". Feel free to supply a pull request if you added and tested a previously unsupported device.
If changes to the configuration lead to an increase in bootloader size, it may be necessary to change the bootloader start address. Please consult "Makefile.inc" for details.
Other make options:
make CONFIG=<config_name> fuse # Configure fuses make CONFIG=<config_name> flash # Upload the bootloader using AVRDUDE
There is also an option to disable the reset line and use it as an I/O. While it may seem tempting to use this feature to make an additional I/O pin available on the ATtiny85, we strongly discourage from doing so, as it led to many issues in the past.
Please "make clean" when switching from one configuration to another.
Micronucleus is widely installed on thousands of open source hardware devices. Please find an incomplete list here: https://github.com/micronucleus/micronucleus/blob/master/Devices_with_Micronucleus.md
This project is released under the GPLv2 license. Code uploaded via the bootloader is not subject to any license.
In addition, we'd like you to consider these points if you intend to sell products using micronucleus:
Please make your hardware open source. At least the schematic needs to be published according to the license inherited from V-USB.
Your documentation should mention Micronucleus and include a link to the main repository (https://github.com/micronucleus/)
Please do not "rebrand" micronucleus by renaming the USB device.
Feel welcome to submit a pull request to include your product in the "Devices using Micronucleus"-list.
v2.0b June 6th, 2015 This pull request documents changes leading to V2.0: https://github.com/micronucleus/micronucleus/pull/43
v2.01 July 26th, 2015 This pull request documents changes leading to V2.1: https://github.com/micronucleus/micronucleus/pull/66
v2.02 August 3rd, 2015
v2.03 February 13th, 2016
v2.04 Dec 8th, 2018
v2.5 March 5th, 2021
v2.6 November 5th, 2021
--infoflag for micronucleus executable.
OSCCAL_HAVE_XTALfor t88 to support MH-ET LIVE Tiny88 boards.