Gaston Salazar-Silva / Mbed 2 deprecated assembly-example

This is a simple example of assembly-language programming inside of an MBED program. It is just a blink program with two functions: setup() and loop().

Dependencies:   mbed

functions.s@0:5446675502f2, 2020-04-22 (annotated)

Committer:
ghsalazar
Date:
Wed Apr 22 15:14:54 2020 +0000
Revision:
0:5446675502f2
Initial commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
ghsalazar 0:5446675502f2 1 ; @file main.S
ghsalazar 0:5446675502f2 2 ; @author Gastón SALAZAR <gaston_salazar@yahoo.com>
ghsalazar 0:5446675502f2 3 ;
ghsalazar 0:5446675502f2 4 ; @brief A blink program for the STM32F446re in assembly.
ghsalazar 0:5446675502f2 5 ; It implements a state machine. It requires a basic
ghsalazar 0:5446675502f2 6 ; C++ main function.
ghsalazar 0:5446675502f2 7 ;
ghsalazar 0:5446675502f2 8 ; This example is used as a didactical resource.
ghsalazar 0:5446675502f2 9
ghsalazar 0:5446675502f2 10 AREA functions_asm, CODE, READONLY
ghsalazar 0:5446675502f2 11
ghsalazar 0:5446675502f2 12 ; Interface
ghsalazar 0:5446675502f2 13
ghsalazar 0:5446675502f2 14 ; @def LED
ghsalazar 0:5446675502f2 15 ; @brief The bit address of pin 5 on port A.
ghsalazar 0:5446675502f2 16 LED EQU (1 << 5)
ghsalazar 0:5446675502f2 17
ghsalazar 0:5446675502f2 18 ; @def DELAY
ghsalazar 0:5446675502f2 19 ; @brief The number of loops to execute before changing th state of LED.
ghsalazar 0:5446675502f2 20 DELAY EQU 5000000
ghsalazar 0:5446675502f2 21
ghsalazar 0:5446675502f2 22 RCC_AHB1ENR EQU 0x40023830 ; Register for enabling the AHB1 clock for GPIOA
ghsalazar 0:5446675502f2 23 GPIOAEN EQU (1 << 0)
ghsalazar 0:5446675502f2 24
ghsalazar 0:5446675502f2 25 GPIOA EQU 0x40020000 ; Base address of port-A registers
ghsalazar 0:5446675502f2 26
ghsalazar 0:5446675502f2 27
ghsalazar 0:5446675502f2 28 GPIO_MODER EQU 0x00 ; Offsets of the registers for port X,
ghsalazar 0:5446675502f2 29 GPIO_PUPDR EQU 0x0c ; using as base the port address
ghsalazar 0:5446675502f2 30 GPIO_ODR EQU 0x14
ghsalazar 0:5446675502f2 31
ghsalazar 0:5446675502f2 32 RESET_MODER5 EQU (3 << 10) ; Bit addresses in the port registers, in order to configure the behaviour of the output pin
ghsalazar 0:5446675502f2 33 SET_MODER5 EQU (1 << 10)
ghsalazar 0:5446675502f2 34 RESET_PUPDR5 EQU (3 << 10)
ghsalazar 0:5446675502f2 35
ghsalazar 0:5446675502f2 36 EXPORT setup
ghsalazar 0:5446675502f2 37
ghsalazar 0:5446675502f2 38 setup ; Machine setup
ghsalazar 0:5446675502f2 39
ghsalazar 0:5446675502f2 40 ; Enable port A
ghsalazar 0:5446675502f2 41 LDR R0, =RCC_AHB1ENR ; R0 = RCC_AHB1ENR
ghsalazar 0:5446675502f2 42 LDR R1, [R0] ; R1 = *R0
ghsalazar 0:5446675502f2 43 ORR R1, R1, #GPIOAEN ; R1 = R1 | GPIOAEN
ghsalazar 0:5446675502f2 44 STR R1, [R0] ; *R0 = R1
ghsalazar 0:5446675502f2 45
ghsalazar 0:5446675502f2 46 ; A minimal initialization for PA5 as output (LED) on the STM32F446re
ghsalazar 0:5446675502f2 47 LDR R3, =GPIOA
ghsalazar 0:5446675502f2 48
ghsalazar 0:5446675502f2 49 LDR R1, [R3, #GPIO_MODER] ; R1 = R3[GPIO_MODER]
ghsalazar 0:5446675502f2 50 BIC R1, R1, #RESET_MODER5 ; R1 = R1 & ~RESET_MODER5
ghsalazar 0:5446675502f2 51 ORR R1, R1, #SET_MODER5
ghsalazar 0:5446675502f2 52 STR R1, [R3, #GPIO_MODER] ; R3[GPIO_MODER] = R1
ghsalazar 0:5446675502f2 53
ghsalazar 0:5446675502f2 54 LDR R1, [R3, #GPIO_PUPDR]
ghsalazar 0:5446675502f2 55 BIC R1, R1, #RESET_PUPDR5
ghsalazar 0:5446675502f2 56 STR R1, [R3, #GPIO_PUPDR]
ghsalazar 0:5446675502f2 57
ghsalazar 0:5446675502f2 58 ; State initilization
ghsalazar 0:5446675502f2 59 ; LED = 0
ghsalazar 0:5446675502f2 60 LDR R1, [R3, #GPIO_ODR]
ghsalazar 0:5446675502f2 61 BIC R1, R1,#LED
ghsalazar 0:5446675502f2 62 STR R1, [R3, #GPIO_ODR]
ghsalazar 0:5446675502f2 63
ghsalazar 0:5446675502f2 64 BX LR
ghsalazar 0:5446675502f2 65
ghsalazar 0:5446675502f2 66 ALIGN
ghsalazar 0:5446675502f2 67 EXPORT loop
ghsalazar 0:5446675502f2 68 loop
ghsalazar 0:5446675502f2 69 ; State update
ghsalazar 0:5446675502f2 70 LDR R3, =GPIOA
ghsalazar 0:5446675502f2 71 LDR R0, =DELAY
ghsalazar 0:5446675502f2 72 loop1
ghsalazar 0:5446675502f2 73 CBNZ R0, wait ; if (R0!=0) goto wait
ghsalazar 0:5446675502f2 74 LDR R1, [R3, #GPIO_ODR]
ghsalazar 0:5446675502f2 75 EOR R1, R1, #LED ; R1 = R1 ^ LED
ghsalazar 0:5446675502f2 76 STR R1, [R3, #GPIO_ODR]
ghsalazar 0:5446675502f2 77 LDR R0, =DELAY
ghsalazar 0:5446675502f2 78 wait
ghsalazar 0:5446675502f2 79 SUB R0, R0, #1 ; R0 = R0 - 1
ghsalazar 0:5446675502f2 80 B loop1 ; goto loop
ghsalazar 0:5446675502f2 81
ghsalazar 0:5446675502f2 82 BX LR ; end of function main, to never be reached
ghsalazar 0:5446675502f2 83 END