# imports
from machine import Pin, ADC, Timer
import math
import time

#######################################
# Pin and constant definitions
#######################################
SEVEN_SEGMENT_START_PIN = 0
ANALOGUE_INPUT_PIN = 26
DISPLAY_COUNT = 4
MEASUREMENT_COUNT = 16
DECIMAL_PRECISION = 3
ADC_RANGE = float((math.pow(2, 16) - 1))
button_1 = Pin(16, Pin.IN, Pin.PULL_UP)

# HEX values for 7 segment display values
digit_list_hex = [
    0x40,  # 0
    0x79,  # 1
    0x24,  # 2
    0x30,  # 3
    0x19,  # 4
    0x12,  # 5
    0x02,  # 6
    0x78,  # 7
    0x00,  # 8
    0x10,  # 9
    0x08,  # A
    0x03,  # B
    0x46,  # C
    0x21,  # D
    0x06,  # E
    0x0E,  # F
    0x7F   # Empty
]

#######################################
# Global variables
#######################################
display_value = 0
segment_pins = []
display_select_pins = []
analogue_voltage_pin = None
current_display_index = DISPLAY_COUNT - 1
display_timer = None
prev_analogue_voltage = -1

#######################################
# Function definitions
#######################################

# Function to read the ADC pin and convert the digital value to a voltage level
def read_analogue_voltage(pin):
    global display_value, prev_analogue_voltage, DECIMAL_PRECISION

    total_value = 0
    for _ in range(MEASUREMENT_COUNT):
        total_value += pin.read_u16()
    average_value = total_value // MEASUREMENT_COUNT

    analogue_voltage = round((average_value / ADC_RANGE) * 3.3, DECIMAL_PRECISION)

    new_display_value = int(analogue_voltage * math.pow(10, DECIMAL_PRECISION))

    if display_value != new_display_value:
        print(f'voltage: {analogue_voltage} mV')
        display_value = new_display_value
        disable_display_timer()
        current_display_index = DISPLAY_COUNT -1
        display_digit(16, -1)
        time.sleep(0.1)
        enable_display_timer()

# Function to disable timer that triggers scanning 7 segment displays
def disable_display_timer():
    global display_timer
    display_timer.deinit()

# Function to enable timer that triggers scanning 7 segment displays
def enable_display_timer():
    global display_timer
    display_timer.init(period=4, mode=Timer.PERIODIC, callback=scan_display)

# Function to handle scanning 7 segment displays
def scan_display(timer):
    global current_display_index, display_value

    digit = int((abs(display_value) // math.pow(10, current_display_index))) % 10
    display_digit(digit, current_display_index,
                  current_display_index == DECIMAL_PRECISION and 0 != DECIMAL_PRECISION)

    current_display_index = (current_display_index - 1)
    if current_display_index < 0:
        current_display_index = DISPLAY_COUNT - 1

# Function to display the given value on the display with the specified index
def display_digit(digit_value, digit_index, dp_enable=False):
    if digit_value < 0 or digit_value > len(digit_list_hex):
        return

    for pin in display_select_pins:
        pin.value(0)

    mask = digit_list_hex[digit_value]
    for i in range(7):
        segment_pins[i].value((mask >> i) & 1)

    segment_pins[7].value(1 if dp_enable == False else 0)

    if digit_index == -1:
        for pin in display_select_pins:
            pin.value(1)
    elif 0 <= digit_index < DISPLAY_COUNT:
        display_select_pins[digit_index].value(1)

# Function to setup GPIO/ADC pins, timers and interrupts
def setup():
    global segment_pins, display_select_pins, analogue_voltage_pin, display_timer

    for i in range(SEVEN_SEGMENT_START_PIN + 8, SEVEN_SEGMENT_START_PIN + 8 + DISPLAY_COUNT):
        pin = Pin(i, Pin.OUT)
        pin.value(0)
        display_select_pins.append(pin)

    for i in range(SEVEN_SEGMENT_START_PIN, SEVEN_SEGMENT_START_PIN + 8):
        pin = Pin(i, Pin.OUT)
        pin.value(1)
        segment_pins.append(pin)

    analogue_voltage_pin = ADC(ANALOGUE_INPUT_PIN)

    display_timer = Timer()
    enable_display_timer()

button_pressed = False

# Interrupt handler for the button press
def int_handler(pin):
    global button_pressed
    button_pressed = True

button_1.irq(trigger=Pin.IRQ_FALLING, handler=int_handler)

if __name__ == '__main__':
    setup()

    while True:
        if button_pressed:
            read_analogue_voltage(analogue_voltage_pin)
            button_pressed = False

        time.sleep(0.1)