AVRUSBBoot - USB bootloader for Atmel AVR controllers
AVRUSBBoot is a bootloader for the Atmel AVR controllers. It uses a
firmware-only USB driver to transfer binary data from the PC to the
flash of the controller. Once the AVR is flashed with the bootloader,
no other ISP programmer is needed; then the microcontroller can be reprogrammed over
Software works under multiple platforms. Linux, Mac OS X and Windows are tested.
Tested with ATMega8-16
No special USB controllers or smd components are needed.
Bootloader fits into 1024 word bootloader block
Basically AVRUSBBoot can be used with all circuits which are supported by the AVR USB driver.
To switch between the bootloader and the application, an aditional jumper is necessary.
Here is an example (Here the levels on the data lines are 5V which doesn't meet the
USB specification! The supply voltage should be regulated to 3,3V - 3,6V):
Firmware and adaptation
The firmware has to be adapted to your hardware. All necessary changes has
to be done in the following two files:
bootloaderconfig.h: Define the condition when the bootloader should be started, e.g. if
a special pin is put to ground with a jumper, and the initialisation of the hardware.
usbconfig.h: Define the used data line pins. You have to adapt USB_CFG_IOPORT,
USB_CFG_DMINUS_BIT and USB_CFG_DPLUS_BIT to your hardware. The rest should be left
Compile the firmware. You need avr-gcc, avr-binutils and avr-libc:
$ cd firmware
The bootloader firmware has to be written to the controller with a ISP programmer.
Once the bootloader is flashed, you don't need a programmer and you can download the
binary data over USB. Don't forget to set the fuses for the external clock source when
flashing the bootloader for the first time!
A C++ tool for downloading hex files is provided.
To compile the program, you need libusb.
$ cd software
When the device is connected and
the bootloader is started (set the jumper before connecting the device), hex files can
be written to the flash of the microcontroller: