87 lines
4.5 KiB
Markdown
87 lines
4.5 KiB
Markdown
This is an implementation of the DFU mode of the [USB DFU Device Class Specification](https://usb.org/document-library/device-firmware-upgrade-11-new-version-31-aug-2004) for the Microchip SAM D5x/E5x micro-controller.
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It is meant to be used as bootloader to allow flashing the main application over USB.
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The code has been developed using a [SAM E54](https://www.microchip.com/wwwproducts/en/ATSAME54P20A) micro-controller.
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It should work on any chip of the SAM D5x/E5x device family by replacing the corresponding device-specific definitions (usually including the chip name in the file name).
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The code uses the [Atmel START](https://start.atmel.com/) ASFv4 library.
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Board
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=====
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The code can be compiled for specific boards:
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- Microchip [SAM E54 Xplained Pro](https://www.microchip.com/DevelopmentTools/ProductDetails/PartNo/ATSAME54-XPRO) development board, named *SAME54_XPLAINED_PRO*
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- sysmocom sysmoOCTSIM, name *SYSMOOCTSIM*
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The board name can be set in 'gcc/Makefile' *BOARD* variable, or provided while compiling (e.g. `make BOARD=SAME54_XPLAINED_PRO`).
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*SAME54_XPLAINED_PRO* is the default value.
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USB DFU
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=======
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This implementation support the following USB DFU capabilities:
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* can download: allowing to download the code over USB on the device (enabled per default)
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* manifestation tolerant: allowing to download after a previous download (disabled per default)
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* will detach: forcing the device the reset after a download, else it wit for a USB reset (enable per default)
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Set the corresponding attributes in the 'DFUD_IFACE_DESCB' macro definition in the 'usb/class/dfu/device/dfudf_desc.h' file.
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To force the DFU bootloader to start there are several possibilities:
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* if the application following the bootloader is invalid (e.g. MSP is not in RAM)
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* if a button is pressed (the button defined in *BUTTON_FORCE_DFU*)
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* if the magic value "DFU!" (e.g. 0x44465521) is set at the start of the RAM (e.g. by the main application when performing a USB detach)
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Compiling
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=========
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Use the 'Makefile' script to compile the source code using the ARM none EABI GCC cross-compiling toolchain:
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```
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cd gcc
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make
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```
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The board name can be set in 'gcc/Makefile' *BOARD* variable, or provided while compiling (e.g. `make BOARD=SAME54_XPLAINED_PRO`).
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*SAME54_XPLAINED_PRO* is the default value.
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The resulting firmware binary is `bootloader-$(BOARD)-$(GIT_VERSION).bin`.
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Flashing
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========
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The USB DFU bootloader should be flashed in a protected area of the flash memory to prevent for erasing it, as specified in data sheet section 25.6.2 Memory Organization.
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The bootloader size is configured in the NVM user configuration BOOTPROT field, as specified in data sheet section 25.6.9 NVM User Configuration.
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The bit position of the BOOTPROT field is documented in data sheet section 9.4 NVM User Page Mapping.
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We need to reserve as least 2 pages of 8192 bytes for the bootloader since it is a bit larger than 10 KB (e.g. over 8 KB).
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This setting will also tell the bootloader where to flash the application firmware to (e.g. after the bootloader reserved space).
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The LED will blink once per second if this size is not set.
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EDBG
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----
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To flash the bootloader using the [edbg tool](https://github.com/ataradov/edbg) over the EDBG interface of the SAM E54 Xplained Pro development board.
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To flash the USB DFU bootloader, perform the following actions:
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* remove reserved bootloader space so we can erase it: `edbg --target atmel_cm4v2 --fuse wv,29:26,15`
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* erase the whole flash: `edbg --target atmel_cm4v2 --fuse v,29:26,15 --erase`
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* program the bootloader: `edbg --target atmel_cm4v2 --fuse v,29:26,15 --program --verify --file bootloader-BOARD-XXXX.bin`
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* reserve bootloader space: `edbg --target atmel_cm4v2 --fuse wv,29:26,13`
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SWJ
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---
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The bootloader can also be flashed over SWJ (e.g. JTAG or SWD).
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You need to perform the following actions:
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* remove reserved bootloader space so we can erase it (and reset MCU for change to be effective)
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* erase the whole flash
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* program the bootloader
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* reserve bootloader space
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Using OpenOCD (with the [SAM E54 patch](http://openocd.zylin.com/#/c/4272/)) and a ST-LINK/V2 SWD adapter, run the following command:
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`openocd --file interface/stlink.cfg --command "transport select hla_swd" --command "set CHIPNAME same54" --command "set CPUTAPID 0x2ba01477" --file target/atsame5x.cfg --command "init" --command "reset halt" --command "atsame5 bootloader 0" --command "flash erase_sector 0 0 last" --command "reset halt" --command "program ./bootloader.bin" --command "atsame5 bootloader 16384" --command "reset run" --command "shutdown"`
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