working demo

lab3subroutines/src/delay.s

@@ -0,0 +1,38 @@
+# delay.s
+# Trevor Barnes
+# CE2801-031
+# Description: A file for handling delay routines
+
+
+.global delay_ms
+# A subroutine to create a delay of a certain number of milliseconds
+# Input: 
+#       r0: Length of delay (ms)
+delay_ms:
+
+    push {r1,r2,r3}
+    mov r3,r0
+ms_delay:
+	# 250 iterations = 1/16 of a millisecond
+    mov r2, #0x10
+# Loop 16 times
+1:
+	# 250
+	mov r1, #0xFA
+# Loop 250 times
+2:
+    sub r1, #1
+    cmp r1, #0
+    bne 2b
+
+    sub r2, #1
+    cmp r2, #0
+    bne 1b
+
+	sub r0, #1
+	cmp r0, #0
+    bne ms_delay
+
+    mov r0,r3
+    pop {r1,r2,r3}
+    bx lr

lab3subroutines/src/led.s

@@ -23,3 +23,104 @@
     .equ GPIO_MODER, 0x00
     # GPIO Output Data Register
     .equ GPIO_ODR, 0x14
+
+.global num_to_LED_init
+# Initializes the GPIO port pins to be outputs
+num_to_LED_init:
+    
+    # Store registers before use
+    push {r1,r2,r3}
+
+    
+    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]
+
+    # Return the original register values
+    pop {r1,r2,r3}
+    # Branch back to link location
+    bx lr
+
+.global LED_test_loop
+
+LED_test_loop:
+
+    push {r0,r1,r2,lr}
+
+    bl num_to_LED_init
+    ldr r1, =GPIOB_BASE
+
+loop:
+
+    ldr r2,[r1,#GPIO_ODR]
+    orr r2,r2,#0x0020
+    str r2,[r1,#GPIO_ODR]
+
+    mov r0, #0x3E8
+    bl delay_ms
+
+    ldr r2,[r1,#GPIO_ODR]
+    bic r2,r2,#0x0020
+    str r2,[r1,#GPIO_ODR]
+
+    mov r0, #0x3E8
+    bl delay_ms
+
+    b loop
+
+    pop {r0,r1,r2,pc}
+
+.global num_to_LED
+# Takes in a 10-bit value and displays it on the LEDs in binary
+# Input:
+#       r0: Input binary value
+num_to_LED:
+
+    push {r1,r2,lr}
+
+    bl num_to_LED_init
+    # Extract "pre-PB11" bit field
+    ubfx r1, r0, #0, #6
+    # extract "post-PB11" bit field
+    ubfx r2, r2, #6, #4
+    # Clear input register
+    mov r0, #0
+    # Insert bit field PB5-PB10
+    bfi r0, r1, #5, #6
+    # Insert bit field PB12-PB15
+    bfi r0, r2, #12, #4
+
+    # Clear register values before use
+    mov r1, #0
+    mov r2, #0
+    ldr r1, =GPIOB_BASE
+
+    ldr r2,[r1,#GPIO_ODR]
+    bfc r2,#0,#16
+    str r2,[r1,#GPIO_ODR]
+
+    ldr r2,[r1,#GPIO_ODR]
+    orr r2,r2,r0
+    str r2,[r1,#GPIO_ODR]
+
+    pop {r1,r2,pc}
+    bx lr

lab3subroutines/src/main.s

@@ -12,4 +12,136 @@
 .global main
 
 main:
+	mov r0, #0
+	mov r1, #0
+	mov r2, #0
 
+main_loop:
+
+    mov r0, #1234
+    bl num_to_ASCII
+    mov r1, r0
+    # r1 is 4 character ASCII value
+    mov r0, #500
+    # Display 1
+   	ubfx r0, r1, #24, #8
+    bl num_to_LED
+    mov r0, #500
+    bl delay_ms
+    # Display 2
+    ubfx r0, r1, #16, #8
+    bl num_to_LED
+    mov r0, #500
+    bl delay_ms
+    # Display 3
+    ubfx r0, r1, #8, #8
+    bl num_to_LED
+    mov r0, #500
+    bl delay_ms
+    # Display 4
+    ubfx r0, r1, #0, #8
+    bl num_to_LED
+    mov r0, #500 
+    bl delay_ms
+    b main_loop
+
+
+end:
+    b end
+.global num_to_ASCII
+
+# Takes in a value from 0-9999 and converts it to ASCII
+# Input:
+#       r0: Input binary value
+# Output:
+#       r1: Output 4 ASCII characters
+num_to_ASCII:
+
+    # If outside of range, return ASCII "Err."
+    push {r1,r2,r3,lr}
+
+    cmp r0,#0
+    blt out_of_range
+    @ cmp r0,#9999
+    @ bgt out_of_range
+
+    # Normal conversion behavior
+    mov r1, #16
+    lsl r0, #3
+    sub r1, #3
+shift_cycle:
+
+    lsl r0, #1
+    sub r1, #1
+
+# Verify Each Nibble is less than or equal to 4
+    ubfx r2, r0, #16, #4
+    # If value is less than or equal to 4, then skip to next nibble
+    cmp r2, #4
+    ble 2f
+    add r2, #3
+    bfi r0, r2, #16, #4
+2:  ubfx r2, r0, #20, #4
+    # If value is less than or equal to 4, then skip to next nibble
+    cmp r2, #4
+    ble 3f
+    add r2, #3
+    bfi r0, r2, #20, #4
+3:  ubfx r2, r0, #24, #4
+    # If value is less than or equal to 4, then skip to next nibble
+    cmp r2, #4
+    ble 4f
+    add r2, #3
+    bfi r0, r2, #24, #4
+4:  ubfx r2, r0, #28, #4
+    # If value is less than or equal to 4 skip to end
+    cmp r2, #4
+    ble end_verify_nibbles
+    add r2, #3
+    bfi r0, r2, #28, #4
+end_verify_nibbles:
+
+    # If value hasn't been shifted 16 times, shift again
+    cmp r1, #0
+    bne shift_cycle
+    mov r3, #3
+# Encode BCD numbers to ASCII
+
+    # Extract ones nibble
+    ubfx r2, r0, #16, #4
+    # Insert ones nibble
+    bfi r1, r2, #0, #4
+    # Insert 3 in front of nibble for ASCII encoding
+    bfi r1, r3, #4, #4
+
+    # Extract tens nibble
+    ubfx r2, r0, #20, #4
+    # Insert tens nibble
+    bfi r1, r2, #8, #4
+    # Insert 3 in front of nibble for ASCII encoding
+    bfi r1, r3, #12, #4
+
+    # Extract hundreds nibble
+    ubfx r2, r0, #24, #4
+    # Insert hundreds nibble
+    bfi r1, r2, #16, #4
+    # Insert 3 in front of nibble for ASCII encoding
+    bfi r1, r3, #20, #4
+
+    # Extract thousands nibble
+    ubfx r2, r0, #28, #4
+    # Insert thousands nibble
+    bfi r1, r2, #24, #4
+    # Insert 3 in front of nibble for ASCII encoding
+    bfi r1, r3, #28, #4
+
+    b end_ASCII
+out_of_range:
+    # Insert ASCII "Err."
+    movw r1, #0x722E
+    movt r1, #0x4572
+
+end_ASCII:
+	mov r0, r1
+    pop {r1,r2,r3,lr}
+    bx lr