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lab2barnestr/src/main.s

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+# main.s
+# Trevor Barnes
+# CE2801-031
+# Lab 2: Knight Rider Lights
+# Description: This 
+
+# Lights are on PB5-PB15 except PB11
+
+.syntax unified
+.cpu cortex-m4
+.thumb
+.section .text
+
+    # Base RCC
+    .equ RCC_BASE, 0x40023800
+    .equ RCC_AHB1ENR, 0x30
+    .equ RCC_GPIOBEN, 1<<1
+
+    .equ GPIOB_BASE, 0x40020400
+    # GPIO Mode Register
+    .equ GPIO_MODER, 0x00
+    # GPIO Output Data Register
+    .equ GPIO_ODR, 0x14
+
+.global main
+
+main:
+
+    # Turn on GPIOB in RCC
+    ldr r1, =RCC_BASE
+
+    # Read, Modify, Write
+    ldr r2, [r1, #RCC_AHB1ENR]
+    orr r2, r2, #RCC_GPIOBEN
+    str r2, [r1, #RCC_AHB1ENR]
+
+    # Enable PB5-PB10, PB12-PB15 to be outputs
+
+    ldr r1, =GPIOB_BASE
+
+    ldr r2, [r1, #GPIO_MODER]
+
+    movw r3, #0x5400
+    movt r3, #0x5515
+    orr r2, r2, r3
+
+    movw r3, #0xA800
+    movt r3, #0xAA2A
+    bic r2, r2, r3
+
+    str r2, [r1, #GPIO_MODER]
+
+turn_on:
+    # Turn on all lights
+    ldr r2, [r1, #GPIO_ODR]
+    movw r3, #0xF7E0
+    orr r2, r2, r3
+    str r2, [r1, #GPIO_ODR]
+
+    # Wait
+    bl delay
+    
+    # Turn of all lights
+    ldr r2, [r1, #GPIO_ODR]
+    movw r3, #0xF7E0
+    orr r2, r2, r3
+    str r2, [r1, #GPIO_ODR]
+    # Wait
+
+    # Go back to turn on al lights
+    b turn_on
+
+delay:
+    ldr r12, =0x002000000
+1:
+
+    subs r12, r12,#1
+    # Bracnch backward to local label if not equal to 0
+    bne 1b
+    bx lr
+end:
+    b end