Add options for generating UF2 image for bootloader, and set up linker symbol for bootloader config

Makefile

@@ -5,13 +5,26 @@ BMP_PORT        ?= /dev/ttyBmpGdb
 
 COMFLAGS=-g -Os -pedantic -Wall
 
-CFLAGS=$(COMFLAGS) -std=c99 -D_POSIX_C_SOURCE=200809L
+LIBNAME     = opencm3_stm32f4
+FP_FLAGS   ?= -mfloat-abi=hard -mfpu=fpv4-sp-d16
+ARCH_FLAGS  = -mthumb -mcpu=cortex-m4 $(FP_FLAGS)
+DEVDEFS     = -DSTM32F4 -DSTM32F4CCM -DSTM32F405RG -D_ROM=1008K -D_RAM=128K -D_CCM=64K -D_CCM_OFF=0x10000000 -D_ROM_OFF=0x08004000 -D_RAM_OFF=0x20000000
+CFLAGS=$(COMFLAGS) $(DEVDEFS) -std=c99 -D_POSIX_C_SOURCE=200809L
 CXXFLAGS=$(COMFLAGS) -std=c++17
 
+LDSCRIPT = linker.ld
+
 OBJS = usb.o adc.o ringbuffer.o uart.o buttons.o printf.o encoder.o
 BINARY ?= main
-DEVICE=STM32F405RG
 
 printf.o: CFLAGS:=$(CFLAGS) -Wno-parentheses -Wno-char-subscripts -Wno-sign-compare -Wno-implicit-fallthrough
 
 include ../rules.mk
+
+uf2: main.uf2
+
+main.uf2: main.bin
+	uf2conv.py -c -b 0x4000 -o $@ $<
+
+
+.PHONY: uf2

linker.ld

@@ -0,0 +1,78 @@
+EXTERN(vector_table)
+ENTRY(reset_handler)
+
+_estack = ORIGIN(ram) + LENGTH(ram);
+_board_dfu_dbl_tap = _estack;
+
+MEMORY
+{
+ ram (rwx) : ORIGIN = 0x20000000, LENGTH = 128K - 4
+ rom (rx) : ORIGIN = 0x08004000, LENGTH = 1024K - 16K
+ ccm (rwx) : ORIGIN = 0x10000000, LENGTH = 64K
+}
+SECTIONS
+{
+ .text : {
+  *(.vectors)
+  *(.text*)
+  . = ALIGN(4);
+  *(.rodata*)
+  . = ALIGN(4);
+ } >rom
+ .preinit_array : {
+  . = ALIGN(4);
+  __preinit_array_start = .;
+  KEEP (*(.preinit_array))
+  __preinit_array_end = .;
+ } >rom
+ .init_array : {
+  . = ALIGN(4);
+  __init_array_start = .;
+  KEEP (*(SORT(.init_array.*)))
+  KEEP (*(.init_array))
+  __init_array_end = .;
+ } >rom
+ .fini_array : {
+  . = ALIGN(4);
+  __fini_array_start = .;
+  KEEP (*(.fini_array))
+  KEEP (*(SORT(.fini_array.*)))
+  __fini_array_end = .;
+ } >rom
+ .ARM.extab : {
+  *(.ARM.extab*)
+ } >rom
+ .ARM.exidx : {
+  __exidx_start = .;
+  *(.ARM.exidx*)
+  __exidx_end = .;
+ } >rom
+ . = ALIGN(4);
+ _etext = .;
+ .noinit (NOLOAD) : {
+  *(.noinit*)
+ } >ram
+ . = ALIGN(4);
+ .data : {
+  _data = .;
+  *(.data*)
+  *(.ramtext*)
+  . = ALIGN(4);
+  _edata = .;
+ } >ram AT >rom
+ _data_loadaddr = LOADADDR(.data);
+ .bss : {
+  *(.bss*)
+  *(COMMON)
+  . = ALIGN(4);
+  _ebss = .;
+ } >ram
+ .ccm : {
+  *(.ccmram*)
+  . = ALIGN(4);
+ } >ccm
+ /DISCARD/ : { *(.eh_frame) }
+ . = ALIGN(4);
+ end = .;
+}
+PROVIDE(_stack = ORIGIN(ram) + LENGTH(ram));