Skip to content

Instantly share code, notes, and snippets.

@BobBurns

BobBurns/blinky.s

Created July 31, 2015 16:45
Show Gist options
  • Star 7 You must be signed in to star a gist
  • Fork 2 You must be signed in to fork a gist
  • Save BobBurns/bb601d3432650073a8b4 to your computer and use it in GitHub Desktop.
Save BobBurns/bb601d3432650073a8b4 to your computer and use it in GitHub Desktop.
Download ZIP
blink led on stm32 L1 Discovery with ARM assembly
Raw
blinky.s
@ lets try to blink an LED on the discovery stm32 L1 board
@ uses LED on PB7
@ how to compile and flash:
@ arm-none-eabi-as -mcpu=cortex-m3 blinky.s -o blinky.o
@ arm-none-eabi-ld -v -T stm32.ld -nostartfiles -o blinky.elf blinky.o
@ arm-none-eabi-objcopy -O binary blinky.elf blinky.bin
@ then from st-link (https://github.com/texane/stlink)
@ ./st-flash write ../first_arm/blinky.bin 0x08000000
.thumb
.syntax unified
@ Equates
.equ STACKINIT, 0x20005000
.equ RCC_AHBRSTR, 0x40023810 @ reset register
.equ RCC_AHBENR, 0x4002381C @ enable clock
.equ GPIOB_MODER, 0x40020400 @ port B mode
.equ GPIOB_OTYPER, 0x40020404 @ type push-pull
.equ GPIOB_OSPEEDR, 0x40020408 @ port pin clock speed
.equ GPIOB_PUPDR, 0x4002040C @ pull-up pull-down
.equ GPIOB_ODR, 0x40020414 @ output data
.equ LEDDELAY, 800000
.section .text
.org 0
@ Vectors
vectors:
.word STACKINIT
.word _start + 1
.word _nmi_handler + 1
.word _hard_fault + 1
.word _memory_fault + 1
.word _bus_fault + 1
.word _usage_fault + 1
_start:
ldr r6, = RCC_AHBRSTR
ldr r5, [r6]
orr r5, r5, 0x02 @ set GPIOB reset bit
str r5, [r6]
ldr r5, [r6]
and r5, r5, 0xfffffffd @ clear GPIO reset bit
str r5, [r6]
@ next enable clock on GPIO port B
ldr r6, = RCC_AHBENR
ldr r5, [r6]
orr r5, r5, 0x02
str r5, [r6]
@ now set port B pin 7 to output
ldr r6, = GPIOB_MODER
ldr r5, [r6]
and r5, r5, 0xffff3fff @ clear bits 15 14
orr r5, r5, 0x00004000 @ set bits 15:14 0 1
str r5, [r6]
@ type = push-pull
ldr r6, =GPIOB_OTYPER
ldr r5, [r6]
and r5, r5, 0xFFFFFF7F
str r5, [r6] @ clear bit 7
@ speed 400kHz
ldr r6, =GPIOB_OSPEEDR
ldr r5, [r6]
and r5, r5, 0xFFFF3FFF
str r5, [r6]
@ pull up pull down none
ldr r6, = GPIOB_PUPDR
ldr r5, [r6]
and r5, r5, 0xFFFF3FFF
str r5, [r6]
@ start blinking
ldr r6, = GPIOB_ODR
loop:
ldr r5, [r6]
and r5, r5, 0xFFFFFF7F @clear bit 7 turns LED on
str r5, [r6]
ldr r1, = LEDDELAY
delay1:
subs r1, 1
bne delay1
@ turn off led
ldr r5, [r6]
orr r5, r5, 0x00000080
str r5, [r6]
ldr r1, = LEDDELAY
delay2:
subs r1, 1
bne delay2
b loop
@ if any int gets triggered, just loop
_dummy:
_nmi_handler:
_hard_fault:
_memory_fault:
_bus_fault:
_usage_fault:
add r0, 1
add r1, 1
b _dummy
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment