AREA    GPIO, CODE, READWRITE
    EXPORT lab4
    IMPORT read_from_push_btns
    IMPORT illuminate_RGB_LED
    IMPORT illuminate_LEDs
    IMPORT write_to_7_segs
    IMPORT read_character
    IMPORT output_character
    IMPORT output_string
    IMPORT read_string
    IMPORT div_and_mod

PIODATA EQU 0x8 ; Offset to parallel I/O data register

prompt = "Welcome to lab #4  ",0       ; Text to be sent to PuTTy
menu = "Choose what to do: \n\r1: Display 4-bit binary value on LEDs\n\r2: Input 4-bit binary value using push buttons\n\r3: Display single hex digit on 7-segment display\n\r4: Illuminate RGB LED with a color \n\r5: Quit \n\r\n\r\n\r", 0
instruction_LEDs = "Type the number to be displayed, in lowercase hex, can be between 0 and f \n\r", 0
instruction_buttons = "Press buttons corresponding to '1' bits and hold them down, then press SpaceBar while holding \n\r", 0
instruction_hex = "Type number of desired display (0,1,2,3), followed by digit to display\n\r", 0
instruction_RGBLED = "Type the character corresponding to the desired color (r|g|b|y|p|w)", 0
result = "The value entered is: ", 0

    ALIGN

lab4
    STMFD SP!,{lr}  ; Store register lr on stack


    MOV r0, #0x6F                   ;
    BL illuminate_RGB_LED           ; Turn RGB LED off

    MOV r0, #0x0                    ;
    BL illuminate_LEDs              ; Turn off LEDs
loop
    ; Display menu and read user selection
    LDR r4, =menu
    BL output_string
    BL read_character

    ; Branch to correct code section
    CMP r0, #0x31
    BEQ LEDs
    CMP r0, #0x32
    BEQ buttons
    CMP r0, #0x33
    BEQ hex_on_seven_segs
    CMP r0, #0x34
    BEQ RGBLED
    CMP r0, #0x35
    BEQ done

    ; Subroutine handling LED function
LEDs
    ; Display instructions and read input
    LDR r4, =instruction_LEDs
    BL output_string
    BL read_character
    CMP r0, #0x39
    SUBGT r0, r0, #87

    ; display number on LEDs
    BL illuminate_LEDs
    B loop


    ; Subroutine handling buttons function
buttons
    ; Display instructions
    LDR r4, =instruction_buttons
    BL output_string
    BL read_from_push_btns

    B loop

    ; Subroutine handling displaying hex digit on 7 segs
hex_on_seven_segs
    ; Display instructions and read input
    LDR r4, =instruction_hex
    BL output_string
    BL read_character
    MOV r1, r0
    BL read_character
    BL write_to_7_segs
    B loop


    ; Subroutine handling RGBLED function
RGBLED
    ; Display instructions and read input
    LDR r4, =instruction_RGBLED
    BL output_string
    BL read_character
    BL illuminate_RGB_LED
    B loop



done
    LDMFD SP!, {lr} ; Restore register lr from stack
    BX LR
    END