import time
from machine import SoftI2C, Pin, ADC
from machine_i2c_lcd import I2cLcd

time.sleep(0.1) # Wait for USB to become ready

# LCD Setup
LCDAddress = 0x27
i2c = SoftI2C(scl=Pin(21), sda=Pin(20), freq=400000) # connect scl to GPIO 21, sda to GPIO 20
lcd = I2cLcd(i2c, LCDAddress, 4, 20)

SelectPin = Pin(2, Pin.IN, Pin.PULL_UP)
ScrollPin = Pin(3, Pin.IN, Pin.PULL_UP)
BackPin = Pin(4, Pin.IN, Pin.PULL_UP)

Ohm1 = Pin(10, Pin.IN, Pin.PULL_UP)
Ohm2 = Pin(11, Pin.IN, Pin.PULL_UP)
Ohm3 = Pin(12, Pin.IN, Pin.PULL_UP)
Ohm4 = Pin(13, Pin.IN, Pin.PULL_UP)

CapMeterPin = Pin(15, Pin.IN)

Volt1 = Pin(16, Pin.IN, Pin.PULL_UP)
Volt2 = Pin(17, Pin.IN, Pin.PULL_UP)
Volt3 = Pin(18, Pin.IN, Pin.PULL_UP)
Volt4 = Pin(19, Pin.IN, Pin.PULL_UP)

AmmeterPin = ADC(28)
VoltmeterPin = ADC(27)
OhmmeterPin = ADC(26)


VoltageReference = 3.3 # Voltage of Pico
ADCResolution = 65535 # ADC range of Pico

# Capacitance Meter Setup
RA = 1000
RB_VALUES = [100000, 10000, 1000]

# Voltmeter Setup
# Scaling factors
RANGES = {
"3.3V": 1.0,
"10V": 3.2,
"25V": 8.5,
"50V": 17.0
}

# Menu Setup
MenuOptions = {
    1: "Ammeter         ",
    2: "Capacitance Meter",
    3: "Voltmeter        ",
    4: "Ohmmeter         "
}


# Ammeter Functions
def Get_Current():
  ShuntResistor = 0.5

  RawCurrent = AmmeterPin.read_u16()
  voltageAcrossShunt = (RawCurrent * VoltageReference) / ADCResolution;
  Current = voltageAcrossShunt / ShuntResistor

  return Current

def Display_Current(Current):
  StrCurrent = "{:.2f}A".format(Current)

  lcd.move_to(0,0)
  lcd.putstr("Current:")
  lcd.move_to(0,1)
  lcd.putstr(StrCurrent)

def Ammeter():
    Current = Get_Current()
    Display_Current(Current)


# Capacitance Meter Functions
def measure_frequency(duration=1):
    count = 0
    start = time.ticks_ms()
    
    while time.ticks_diff(time.ticks_ms(), start) < duration * 1000:
        if CapMeterPin.value() == 1:
            while CapMeterPin.value() == 1:
                pass
            count += 1
    
    return count / duration
# Calculate capacitance
def calc_C(f, RB):
    if f == 0:
        return 0
    return 1 / (0.693 * (RA + 2 * RB) * f)
# Auto-range RB
def select_RB(f):
    if f > 2000:
        return 100000   
    elif f > 100:
        return 10000    
    else:
        return 1000 
# Format capacitance
def format_C(C):
    if C >= 1e-6:
        return "{:.2f}uF".format(C * 1e6)
    elif C >= 1e-9:
        return "{:.2f}nF".format(C * 1e9)
    else:
        return "{:.2f}pF".format(C * 1e12)
# Format frequency
def format_f(f):
    if f >= 1000:
        return "{:.1f}kHz".format(f / 1000)
    else:
        return "{:.0f}Hz".format(f)

def CapMeter():
    f = measure_frequency()
    RB = select_RB(f)
    C = calc_C(f, RB)
    
    lcd.move_to(0, 0)
    lcd.putstr("F:" + format_f(f))
    
    lcd.move_to(0, 1)
    lcd.putstr("C:" + format_C(C))
    
    time.sleep(1)


# Voltmeter Functions
def Voltmeter_read_voltage():
      raw = VoltmeterPin.read_u16()
      return (raw / ADCResolution) * VoltageReference

def get_range():
    if not Volt1.value():
        return "3.3V"
    elif not Volt2.value():
        return "10V"
    elif not Volt3.value():
        return "25V"
    elif not Volt4.value():
        return "50V"
    else:
        return None  # nothing selected (bad wiring)

def Display_Voltage(Range, v_actual):
    lcd.move_to(0,0)
    lcd.putstr("Voltage")
    lcd.move_to(0,1)
    lcd.putstr("Range: " + str(Range) + "       ")
    lcd.move_to(0,2)
    lcd.putstr("Vout: " + str(v_actual) + "   ")

def Display_Voltage_No_Range():
    lcd.move_to(0,0)
    lcd.putstr("Voltage")
    lcd.move_to(0,1)
    lcd.putstr("No range selected  ")
    lcd.move_to(0,2)
    lcd.putstr("         ")

def Measure_Voltage():
    current_range = get_range()
 
    if current_range is None:
        Display_Voltage_No_Range()
        time.sleep(0.5)
        return
 
    v_out = Voltmeter_read_voltage()
    v_actual = v_out * RANGES[current_range] # Final Voltage Measurement
    Display_Voltage(current_range, v_out)
    time.sleep(0.5)

def Voltmeter():
    Measure_Voltage()
    time.sleep_ms(200)


# Ohmmeter Functions
def Ohmmeter_read_voltage():
      raw = OhmmeterPin.read_u16()
      return (raw / ADCResolution) * VoltageReference

def get_r_known():
    if not Ohm1.value():
        return "100 Ohms"        # 0–100Ω range
    elif not Ohm2.value():
        return "1k Ohms"       # 100Ω–1kΩ
    elif not Ohm3.value():
        return "10k Ohms"      # 1kΩ–10kΩ
    elif not Ohm4.value():
        return "100k Ohms"     # 10kΩ–100kΩ
    else:
        return None

def measure_resistance():
    r_known = get_r_known()
    if r_known is None:
        return None, None

    v_out = Ohmmeter_read_voltage()

    # invalid region checks (avoid divide errors / saturation)
    if v_out <= 0.001 or v_out >= (VREF - 0.001):
        return r_known, None

    r_unknown = r_known * (v_out / (VREF - v_out))
    return r_known, r_unknown

def Ohmmeter_display(r_known, r_unknown):
    lcd.clear()

    # Line 1: Resistance
    lcd.move_to(0, 0)
    if r_unknown is None:
        lcd.putstr("Resistance:")
    else:
        lcd.putstr("Resistance: " + str(int(r_unknown)))

    # Line 2: Range
    lcd.move_to(0, 1)
    if r_known is None:
        lcd.putstr("Range: NONE")
    else:
        lcd.putstr("Range: " + r_known)

def Ohmmeter():
    r_known, r_unknown = measure_resistance()
    Ohmmeter_display(r_known, r_unknown)
    time.sleep(3)


# Menu Function
def Display_Menu(Selected):
    Selected = MenuOptions[Selected]
    lcd.move_to(0,0)
    lcd.putstr("Menu:")
    lcd.move_to(0,1)
    lcd.putstr(Selected + "    ")

def Menu():
    Selected = 1
    while True:
        Display_Menu(Selected)
        if ScrollPin.value() != 1:
            Selected += 1
            if Selected == 5:
                Selected = 1
            time.sleep(0.2)
        elif SelectPin.value() != 1:
            return Selected
        time.sleep(0.1)

def Main():
    while True:
        time.sleep(1)
        lcd.clear()
        Selected = Menu()
        lcd.clear()
        if Selected == 1:
            while BackPin.value() == 1:
                Ammeter()
                time.sleep(0.1)
        elif Selected == 2:
            while BackPin.value() == 1:
                CapMeter()
                time.sleep(0.1)
        elif Selected == 3:
            while BackPin.value() == 1:
                Voltmeter()
                time.sleep(0.1)
        elif Selected == 4:
            while BackPin.value() == 1:
                Ohmmeter()
                time.sleep(0.1)
        else:
            print("Something's wrong")

Main()