The DFU uses the UART peripheral (with IRQ/ISR) for the debug output
console. Before starting the main application we should make sure
this configuration is reset to avoid interference (particularly the
IRQ/ISR).
This is not too important though since the main application
reconfigures the UART for console output.
Other peripheral could also be disabled (e.g. all other PIO used
by DFU), but most of them also get configured by the main application.
Change-Id: I8234d1b85938ad6393094c08183f613ad09ee01b
The stack size is fixed. The linker script puts the stack section
after the bss section. The initial stack pointer is not at the
end of the RAM (as often seen).
Thus the initial stack pointer address of the main application
is different than the one from DFU. When starting the main
application the stack pointer needs to be set to the new value.
If this is not done the main application stack may overwrite the
data in bss, even without exceeding the fixed stack size.
Change-Id: Ie354d603fe302d3d5bdfa9c31575411de722323b
fixes following warning:
libboard/common/source/board_cstartup_gnu.c:137:11: warning: assignment to 'void (*)(void)' from 'unsigned int' makes pointer from integer without a cast [-Wint-conversion]
appReset = pSrc[1];
The original board startup script is provided by Atmel.
It has been modified to handle application or DFU booting.
The copyright notice has been updated to reflect this change.
Using the USBDFU_OverrideEnterDFU() function, a board/application can
define extra conditions when the system should boot in DFU mode, even if
it was not explicitly switched to DFU mode from the application.
The app/dfu/main.c uses this mechanism to boot into DFU mode if the
stack + reset vector addresses are not plausible (i.e. some random junk
appears to be flashed in the application partition) or if the user
places a jumper accross the RxD+TxD lines of the debug UART. The idea
is that the system can be recovered by placing this jumper and then
re-installing the application from DFU.
It is utterly unacceptable that Atmel is shipping example code in 2011,
which doesn't support parts that are shipped still in 2016. They would
have had five years to fix their code to implement the chip errata :(
This way we can easily check with 'diff' for differences in our code and
Atmel softpack. Also, this layout is more suitable for building various
different firmware images (e.g. factory-test, dfu-loader, main
application) for a variety of different boards (simtrace, owhw, qmod).
