forked from jappel/VersaMCU
Julian Appel
f60a29137c
Hardware-tested the UF2 bootloader end to end on a real VersaPad v2 board. Found and fixed a real bug: the bootloader's jump into the app (__set_MSP -> SCB->VTOR -> bx) hard-faulted on every standalone boot, even with the debugger fully disconnected; identical register/VTOR values injected directly by a halted debugger ran fine, which pointed at the missing __DSB()/__ISB() barriers ARM's own guidance requires for this exact pattern. Also fixed a USB PID collision (0x0011 is Adafruit's own Gemma M0 bootloader PID, misidentified by Windows as a Circuit Playground COM port instead of exposing VERSABOOT). This board has no dedicated reset/boot button, so add a hardware boot entry that doesn't need one: holding the bottom-right Cherry MX key (key_id 24) during reset/power-on drives its matrix row and reads its column directly in the bootloader, before the app is even validated. Also corrected the app-side flash_with_bootloader.ld (was missing the NVM carve-out flash_without_bootloader.ld already has) and boards/versapad.json (wrong flash/RAM size, wrong MCU macro, stale PID), and enabled the previously-commented-out env:versapad_usb. Documented findings in bootloader/README.md, bootloader/TESTING.md, and doc/09_known_limitations.md. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
101 lines
2.2 KiB
Text
101 lines
2.2 KiB
Text
/* Linker script for ATSAMD21G17D – with 8KB bootloader (flash starts at 0x2000) */
|
||
|
||
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
|
||
OUTPUT_ARCH(arm)
|
||
SEARCH_DIR(.)
|
||
|
||
MEMORY
|
||
{
|
||
rom (rx) : ORIGIN = 0x00002000, LENGTH = 0x0001D900 /* 118.25K – Firmware (128K - 8K bootloader - 1.25K NVM) */
|
||
nvm (rx) : ORIGIN = 0x0001FB00, LENGTH = 0x00000500 /* 1.25K – Makros + Config, same layout as flash_without_bootloader.ld */
|
||
ram (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00004000 /* 16K */
|
||
}
|
||
|
||
__StackTop = ORIGIN(ram) + LENGTH(ram);
|
||
__StackLimit = __StackTop - 0x1000;
|
||
|
||
SECTIONS
|
||
{
|
||
.text :
|
||
{
|
||
__text_start__ = .;
|
||
. = ALIGN(4);
|
||
KEEP(*(.isr_vector))
|
||
KEEP(*(.vectors .vectors.*))
|
||
*(.text .text.* .gnu.linkonce.t.*)
|
||
*(.glue_7t) *(.glue_7)
|
||
*(.rodata .rodata* .gnu.linkonce.r.*)
|
||
*(.ARM.extab* .gnu.linkonce.armextab.*)
|
||
|
||
. = ALIGN(4);
|
||
KEEP(*(.init))
|
||
__preinit_array_start = .;
|
||
KEEP(*(.preinit_array))
|
||
__preinit_array_end = .;
|
||
|
||
__init_array_start = .;
|
||
KEEP(*(SORT(.init_array.*)))
|
||
KEEP(*(.init_array))
|
||
__init_array_end = .;
|
||
|
||
KEEP(*crtbegin.o(.ctors))
|
||
KEEP(*(EXCLUDE_FILE(*crtend.o) .ctors))
|
||
KEEP(*(SORT(.ctors.*)))
|
||
KEEP(*crtend.o(.ctors))
|
||
|
||
. = ALIGN(4);
|
||
KEEP(*(.fini))
|
||
__fini_array_start = .;
|
||
KEEP(*(.fini_array))
|
||
KEEP(*(SORT(.fini_array.*)))
|
||
__fini_array_end = .;
|
||
|
||
KEEP(*crtbegin.o(.dtors))
|
||
KEEP(*(EXCLUDE_FILE(*crtend.o) .dtors))
|
||
KEEP(*(SORT(.dtors.*)))
|
||
KEEP(*crtend.o(.dtors))
|
||
|
||
. = ALIGN(4);
|
||
} > rom
|
||
|
||
PROVIDE_HIDDEN(__exidx_start = .);
|
||
.ARM.exidx :
|
||
{
|
||
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
|
||
} > rom
|
||
PROVIDE_HIDDEN(__exidx_end = .);
|
||
|
||
. = ALIGN(4);
|
||
__etext = .;
|
||
_etext = .;
|
||
|
||
.data : AT(__etext)
|
||
{
|
||
. = ALIGN(4);
|
||
__data_start__ = .;
|
||
_srelocate = .;
|
||
*(.ramfunc .ramfunc.*);
|
||
*(.data .data.*);
|
||
. = ALIGN(4);
|
||
__data_end__ = .;
|
||
_erelocate = .;
|
||
} > ram
|
||
|
||
.bss (NOLOAD) :
|
||
{
|
||
. = ALIGN(4);
|
||
__bss_start__ = .;
|
||
_sbss = .;
|
||
_szero = .;
|
||
*(.bss .bss.*)
|
||
*(COMMON)
|
||
. = ALIGN(4);
|
||
__bss_end__ = .;
|
||
_ebss = .;
|
||
_ezero = .;
|
||
} > ram
|
||
|
||
. = ALIGN(4);
|
||
end = .;
|
||
_end = .;
|
||
}
|