First ARM Cortex-M0 firmware

// These are defined in the linker script extern unsigned __dataSrc; extern unsigned __dataDst; extern unsigned __dataDstEnd; extern unsigned __varStackTop; // Unimplemented interrupts void hdlStop(void) { while(1); } // Reset handler, which is the effective entrypoint void hdlReset(void) { // Copy data segment from flash to RAM (redundant in this example) unsigned *src = &__dataSrc; unsigned *dst = &__dataDst; while( dst < &__dataDstEnd ) *dst++ = *src++; // Sets PIO0_1 & PIO0_2 to output without pulldown/pullup *((volatile unsigned int*)0x40044010) = 0xc0; *((volatile unsigned int*)0x4004401c) = 0xc0; // Set bits 1 & 2 of Port 0 to output *((volatile unsigned int*)0x50008000) = 0x06; // Write 0x02 to Port 0 with bitmask disabled (lights one of the LED pins) // The lower 2 bytes can mask out bits that should not be affected by the write. *((volatile unsigned int*)0x50003ffc) = 0x02; // Infinate loop while(1); } // The linker will stick this at 0x0000000. It is a pointer to the top of the // call stack, and the linker provides __varStackTop which contains the value // that should be placed here. __attribute__((section(".stack"),used)) unsigned *ptrStackTop = &__varStackTop; // Exception jump table. __attribute__((section(".handlers"),used)) void (*vecHandlers[])() = { hdlReset, hdlStop, hdlStop, hdlStop, hdlStop, hdlStop, 0xefffee8a, /* Checksum */ hdlStop, hdlStop, hdlStop, hdlStop, hdlStop, hdlStop, hdlStop // Interrupts omitted };

MEMORY { NVM(rx) : ORIGIN = 0x00000000, LENGTH = 16k RAM(rx) : ORIGIN = 0x10000000, LENGTH = 4k } SECTIONS { __varStackTop = ORIGIN(RAM) + LENGTH(RAM); /* Top of stack */ __dataSrc = LOADADDR(.data); . = ORIGIN(NVM); .text : { KEEP( *(.stack) ); /* Top of stack first */ KEEP( *(.handlers) ); /* Interrupt jump table */ KEEP( *(.text) ); /* Other program code */ } >NVM /* Initialised global data (none in this example) */ . = ORIGIN(RAM); .data : { __dataDst = .; *(.data); . = ALIGN(4); __dataDstEnd = .; } >RAM AT >NVM /* Stored in NVM, later copied to RAM */ /* Uninitialised global data (none in this example) */ .bss : { *(.bss); } >RAM }

CC=arm-none-eabi-gcc LD=arm-none-eabi-ld CFLAGS=-Wall -mcpu=cortex-m0 all: first.elf first.o: first.c first.elf: first.o $(LD) $(LDFLAGS) -T first.ld $^ -o $@