.syntax unified                 @ Specify unified assembly syntax
.cpu    cortex-m0plus           @ Specify CPU type is Cortex M0+
.thumb                          @ Specify thumb assembly for RP2040
.global main_asm                @ Provide program starting address to the linker
.align  4                       @ Specify code alignment

.equ SLEEP_TIME, 500                    @ Specify the sleep time (in ms)
.equ    LED_GPIO_PIN, 0         @ Specify the pin that the onboard LED is connected to
.equ    ADC_GPIO_PIN, 26        @ Specify the pin that the potentiometer is connected to
.equ    LED_GPIO_OUT, 1         @ Specify the direction of the GPIO pin
.equ    LED_GPIO_IN, 0          @ Specify the direction of the GPIO pin
.equ    LED_VALUE_ON, 1         @ Specify the value that turns the LED "on"
.equ    LED_VALUE_OFF, 0        @ Specify the value that turns the LED "off"

.equ    ADC_BASE, 0x4004C000    @ Base address of the ADC registers
.equ    ADC_CS,   0x00          @ Offset of the Control and Status Register
.equ    ADC_RESULT, 0x04        @ Offset of the Result Register
.equ    ADC_CS_EN, 0x01         @ Bit 0: Enable ADC
.equ    ADC_CS_START_MANY, 0x08 @ Bit 3: Start Many conversion
.equ    ADC_CH0, 0x00           @ Channel 0 (GPIO26) selection bits
.equ    ADC_READY_BIT_MASK, 0x0100         

@ Entry point to the ASM portion of the program
main_asm:
  movs r5, #0
  init_gpio:
    movs    r0, #LED_GPIO_PIN    @ Load r0 with the value of LED_GPIO_PIN, which is 25
    adds    r0, r0, r5
    bl      asm_gpio_init        @ Call asm_gpio_init with r0=25 (GPIO 25)
    movs    r0, #LED_GPIO_PIN    @ Load r0 with the value of LED_GPIO_PIN, which is 25
    adds    r0, r0, r5
    movs    r1, #LED_GPIO_OUT    @ Load r1 with 1, indicating output direction
    bl      asm_gpio_set_dir     @ Call asm_gpio_set_dir with r0=25, r1=1
    adds    r5, r5, #1
    cmp r5, #10
    bne     init_gpio

    movs    r0, #ADC_GPIO_PIN
    bl      asm_gpio_init
    movs    r0, #ADC_GPIO_PIN    
    movs    r1, #LED_GPIO_IN     
    bl      asm_gpio_set_dir

    ldr     r1, =ADC_BASE       @ Load the base address of the ADC
    ldr     r0, [r1, #ADC_CS]   @ Load the current value of the CS register
    adds    r0, r0, #ADC_CS_EN  @ Set the EN bit to enable the ADC
    str     r0, [r1, #ADC_CS]   @ Write back the value to the CS register
    ldr     r1, [r0, #ADC_CS]     @ Load the current value of the CS register
    ldr     r2, [r0, #ADC_RESULT] @ Load the result from the RESULT register

    poll_adc:
    movs r7, #9
    movs r4, #0

  set_leds:
    cmp     r4, r7               @ Compare LED counter with scaled result
    bge     loop
    movs    r0, #LED_GPIO_IN     @ Load GPIO pin number
    adds    r0, r0, r4
    movs    r1, #LED_VALUE_ON    @ Set pin high
    bl      asm_gpio_put         @ Turn on LED
    adds    r4, r4, #1
    b set_leds
    

  loop:

  b loop

  @ Set data alignment
.data
    .align 4