# imports
import machine
import math
import time
from machine import Timer

#######################################
# Pin and constant definitions
#######################################
Main_Button_PIN = 16
DISPLAY_Count = 4 
DECIMAL_places = 3
ADC_REF_VOLTAGE = 3.3
ADC_RANGE = 65535
DEBOUNCE_TIME_Per_ms = 200

digit_list_hex = [0x40, 0x79, 0x24, 0x30, 0x19, 0x12, 0x02, 0x78, 0x00, 0x10, 0x08, 0x03, 0x46, 0x21, 0x06, 0x0E, 0x7F]

#######################################
# Global variables
#######################################
display_value = 0
pin_list = []
volt_pin = None
select_pin_list = []
but_pin = None
display_signal = DISPLAY_Count - 1
display_timer = None
previous_analogue_voltage = -1
last_button_pressed = 0
debounce_timer = Timer()

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

# Function to read the ADC pin and
# to convert the digital value to a voltage level in the 0-3.3V range
# This function updates the value of the display_value global variable
def read_analogue_voltage(pin):
    global display_value, previous_analogue_voltage
    val = pin.read_u16()
    analogue_voltage = round((val / ADC_RANGE) * ADC_REF_VOLTAGE, DECIMAL_places)
    if analogue_voltage != previous_analogue_voltage:
        previous_analogue_voltage = analogue_voltage
        new_display_value = int(analogue_voltage * 1000)
        if display_value != new_display_value:
            display_value = new_display_value
            reset_display()
        return analogue_voltage

# 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=machine.Timer.PERIODIC, callback=scan_display)

# Function to handle scanning 7 segment displays
# Display the value stored in the display_value global variable
# on available 7-segment displays
def scan_display(timer_interrupt):
    global display_signal, display_value

    digit = int(abs(display_value) // math.pow(10, display_signal)) % 10
    display_digit(digit, display_signal, display_signal == DECIMAL_places)
    display_signal = (display_signal - 1) % DISPLAY_Count

# Function display the given value on the display with the specified index
# dp_enable specifies if the decimal pooint should be on or off
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 select_pin_list:
        pin.value(0)
    mask = digit_list_hex[digit_value]
    for i in range(7):
        pin_list[i].value((mask >> i) & 1)
    pin_list[7].value(not dp_enable)
    if digit_index == -1:
        for pin in select_pin_list:
            pin.value(1)
    elif 0 <= digit_index < DISPLAY_Count:
        select_pin_list[digit_index].value(1)

# Function to handle the button interrupt
def but_interrupt(pin):
    global last_button_pressed
    current_time = time.ticks_ms()
    if current_time - last_button_pressed > DEBOUNCE_TIME_Per_ms:
        last_button_pressed = current_time
        voltage = read_analogue_voltage(volt_pin)
        if voltage is not None:
            print(f'Voltage: {voltage} V')

# Function to setup GPIO/ADC pins, timers and interrupts
def setup():
    global pin_list, select_pin_list, volt_pin, but_pin, display_timer
    select_pin_list = [machine.Pin(i, machine.Pin.OUT) for i in range(8, 8 + DISPLAY_Count)]
    for pin in select_pin_list:
        pin.value(0)
    pin_list = [machine.Pin(i, machine.Pin.OUT) for i in range(0, 8)]
    for pin in pin_list:
        pin.value(1)
    volt_pin = machine.ADC(26)
    but_pin = machine.Pin(Main_Button_PIN, machine.Pin.IN, machine.Pin.PULL_UP)
    # Set up interrupt for the button
    but_pin.irq(trigger=machine.Pin.IRQ_FALLING, handler=but_interrupt)
    display_timer = machine.Timer()
    enable_display_timer()

# The following Function is declared to reset the display
def reset_display():
    global display_signal
    disable_display_timer()
    display_signal = DISPLAY_Count - 1
    display_digit(16, -1)
    time.sleep(0.1)
    enable_display_timer()

# Function to test avaiable 7-segment displays
def display_value_test():
    for i in range(16):
        display_digit(i, 0)
        time.sleep(0.5)

if __name__ == '__main__':
    setup()
    while True:
        time.sleep(1)