This project is still in early development.
USB DFU Bootloader is a second-stage bootloader (SSBL) that acts as a Device Firmware Update (DFU) USB device. It allows you to load application firmware onto an on-board Flash chip via a USB connection to a host computer. Planned improvements are to support loading firmware onto an SDMMC card.
The host computer must run a DFU host such as dfu-util. The user runs a terminal command to transfer a uimg file from the computer to the flash chip on a custom board. The command is something like this:
dfu-util -a 0 -s 0x70080000 -D myfirmware.uimg
The given address (0x70080000) is an address on the flash chip plus 0x70000000. So an address of 0x70090000 means flash address 0x90000, etc. The address must be aligned to 4k sectors. The flash driver assumes the chip has uniform 4k sectors. This can be easily changed to accomodate other chips with different sector layouts.
A recent version of MP1-Boot allows for setting a pin to determine which application to boot. If the pin is detected as pulled-down, firmware from 0x60000 on the flash chip will be loaded and executed. Otherwise, if the pin is detected as pulled-up, firmware from 0x80000 on the flash chip will be loaded and executed.
This was done with USB DFU in mind. A typical use would be to load the USB DFU bootloader firmware to address 0x60000 and the main application to 0x80000 (using an SPI flash loader, or some other means such as J-Link or TRACE32). A button or jumper can be setup so that MP1-Boot jumps into the main application by default. Holding the button down will make it jump to the USB DFU bootloader. From there, the user can flash new application firmware.
The board configuration is currently for the MetaModule PCB version p11. If you
need to adapt this to your own project, edit the file in src/board_conf/.
If you need to change the writeable area of Flash, edit this in
src/usb_dfu/usbd_dfu_media.cc by changing the NORFLASH_DESC_STR string. The
value 3456*4Kg means 3456 sectors of size 4kb each, which is 13.5MB.
The value 0x70080000 is the starting address to allow writing.
You also will need to change the NORFlash constexpr variables below that line.
On Linux, if you see this error:
$ dfu-util -l
...
dfu-util: Cannot open DFU device 0483:df11 found on devnum 29 (LIBUSB_ERROR_ACCESS)
Create a new file inside /etc/udev/rules.d/ and give it a name like metamodule.rules. Enter this into the file:
ACTION=="add", SUBSYSTEM=="usb", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="df11", MODE="664", TAG+="uaccess"
Then, unplug and replug device.