Pre-compiled u8.0 urboot bootloaders
This repository contains pre-compiled AVR bootloaders to be used with the avrdude -c urclock
uploader. They are all in the directory tree
mcus sorted by MCU name, eg,
autobaud bootloaders for the
ATmega328P.
The boards directory contains
urboot bootloaders sorted by board name. Here one can find, eg, autobaud bootloaders for the
venerable ATmega328P based
Uno
with a LED on PB5, the Arduino Pro
Mini
(same bootloaders), the
Jeenode
with a low-active LED on PB1, the ATmega1284P based Moteino
Mega
and the ATmega2560 Mega R3
board;
or, eg, some 16 MHz and 115,200 baud bootloaders for the ATtiny167 based Digispark
Pro,
the ATtiny85 based
Disgispark
and the ATtiny84 based
Luminet.
Finally, there are pre-compiled urboot bootloaders for popular Arduino cores in the
cores directory.
There is a subtle distinction between bootloaders for MCUs driven by an external oscillator, which tend to have a small (< 0.2%) deviation from the nominal FCPU, and MCUs running on an internal oscillator, which more often than not exhibit a deviation of 2% or more from the nominal clock frequency. For the former, the pre-compiled urboot bootloaders tend to be shorter and faster at the cost of potentially higher quantisation errors for the baud rate, up to 2.1%. For the latter the bootloaders tend to be slower but have a baud rate quantisation error of less than 0.5%; there are a number of bootloaders on offer in steps of 1.25% around the nominal FCPU so that a particular board can be furnished with a suitable bootloader for the actual internal clock frequency. All in all the aim is to ensure baud rate errors are below 2.5% to facilitate reliable serial communication.
The pre-compiled .hex bootloaders of the
boards and
cores directories are copies of
selected relevant bootloaders in the
mcus tree, typically engaging the
correct activity LED for visual feedback while the bootloader is active. With these bootloaders the
board LED comes on after an external reset of the board at the beginning of each character read
getch() routine and is switched off at the end of each getch(). When the bootloader times out
at the end of its engagement the LED is switched off (unless, of course, it is used thereafter in
the uploaded application). There is no need to select a bootloader with
blinkenlights: a silent bootloader from the
corresponding mcus tree which has
_no-led in the filename would equally be suitable for the board/core in consideration.
All in all, this repository contains 1,119,102 different current u8.0 bootloaders amongst the
8,044,668 bootloader files on offer in the
mcus tree (4,611,934), the
boards tree (1,080,684) and the
cores tree (2,352,050). One reason
why some bootloaders are copies of each other is because, eg, a bootloader on 115,200 baud for 16
MHz is exactly the same as a bootloader on 57,600 baud for 8 MHz. The copies under different
names and boards/cores directories are provided for convenience.
The 1,283,806 different bootloaders of the previous version in the
u7.7 directory tree are less
interesting as they are usually bigger for the same features; none of them has the update feature
introduced in u8.0. The u7.7 directory contains, however, a number of now deprecated s-type
bootloaders that follow a skeleton STK500v1 protocol; these bootloaders can be used with avrdude -c arduino and older avrdude versions instead of the avrdude -c urclock programmer that urboot
bootloaders otherwise require.
Click on the links below to get more information about
- The urboot project
- Its background
- Compiling your own bootloader using urboot make options
- Selecting the right bootloader for you
- Using them
- How they compare to optiboot
- And, finally, how to trouble-shoot them if things go wrong
Cloning this repository can take long and create a large directory (some 120 GB). Pro tip: Download a zip file instead from github or execute on the command line
curl -L https://github.com/stefanrueger/urboot.hex/tarball/master >urboot-hex.tar
This creates 3.4 GB gzip compressed tar file from the current snapshot.