@ mycode.s : @ Test code for STM32 and linking assembly to C

@ This is a comment. Anything after an @ symbol is ignored. @@ This is also a comment. Some people use double @@ symbols.

.code 16 @ This directive selects the instruction set being generated. @ The value 16 selects Thumb, with the value 32 selecting ARM.

.text @ Tell the assembler that the upcoming section is to be considered @ assembly language instructions - Code section (text -> ROM)

@@ Function Header Block .align 2 @ Code alignment - 2^n alignment (n=2) @ This causes the assembler to use 4 byte alignment

.syntax unified @ Sets the instruction set to the new unified ARM + THUMB @ instructions. The default is divided (separate instruction sets)

.global mytest @ Make the symbol name for the function visible to the linker

.code 16 @ 16bit THUMB code (BOTH .code and .thumb_func are required) .thumb_func @ Specifies that the following symbol is the name of a THUMB @ encoded function. Necessary for interlinking between ARM and THUMB code.

.type mytest, %function @ Declares that mytest symbol is a function (not strictly required)

@ Function Declaration : int mytest(int x) @ @ Input: r0 (i.e. r0 holds x) @ Returns: r0 @

@ Here is the actual function mytest:

push {r4-r7, lr} @ Put aside registers we want to restore later

mov r0, #1 @ r0 holds our argument for the LED toggle function @ So pass it a value

bl BSP_LED_Toggle @ call BSP C function using Branch with Link (bl)

ldr r1, =myTickCount ldr r0, [r1]

pop {r4-r7, lr} @ Bring all the register values back

bx lr @ Return (Branch eXchange) to the address held in the link register (lr)

.size mytest, .-mytest @@ - symbol size (not req)

@@ Function Header Block .align 2 @@ 2^n alignment (n=2) .syntax unified @@ Unified Syntax .global my_Tick @@ Expose my_Tick to the linker .code 16 @@ - 16bit THUMB code (BOTH are required!) .thumb_func @@ /

.type my_Tick, %function @@ - symbol type (not req)

@@ Declaration : void my_Tick( void ) @@ Uses nothing

my_Tick:

push {lr}

ldr r1, =myTickCount @@ Address of myTickCount stored in r1 ldr r0, [r1] @@ Load r0 with the address pointed at by r1 (myTickCount address) add r0, r0, #1 @@ Increment r0 str r0, [r1] @@ Store the current r0 value back to the address pointed at by r1

pop {lr}

bx lr @@ Return to the address stored in lr

.size my_Tick, .-my_Tick @@ - symbol size (not req)

@@ .align 2 @@ - 2^n alignment (n=2) .syntax unified .global my_Loop @@ - Symbol name for function .code 16 @@ - 16bit THUMB code (BOTH are required!) .thumb_func @@ / .type my_Loop, %function @@ - symbol type (not req) @@ Declaration : void my_Loop( void ) @@ Uses nothing my_Loop: push {lr} pop {pc} .size my_Loop, .-my_Loop @@ - symbol size (not req)

@@ .align 2 @@ - 2^n alignment (n=2) .syntax unified .global my_Init @@ - Symbol name for function .code 16 @@ - 16bit THUMB code (BOTH are required!) .thumb_func @@ / .type my_Init, %function @@ - symbol type (not req)

@@ Declaration : void my_Init( void ) @@ Uses nothing my_Init: bx lr @@push {lr} @@pop {pc} .size my_Init, .-my_Init @@ - symbol size (not req)

@ Program Data section - Items declared here are read/write

.data

.global myTickCount @ Expose the symbol to the linker

@ Actual declaration of the symbol myTickCount: .word 1 @ A 32-bit variable named myTickCount

@ Assembly file ended by single .end directive on its own line .end

Things past the end directive are not processed, as you can see here.

modify the code 1. Toggles all 8 LEDs using a loop. To make your life easier, they do not need to be in order. 2. Delays between LEDs toggling according to the delay passed by the user. 3. Repeats this cycle the number of times specified by the user