from machine import Pin, ADC, I2C
import ssd1306
from time import sleep

i2c  = I2C(0, sda=Pin(0), scl=Pin(1), freq=400000)
oled = ssd1306.SSD1306_I2C(128, 64, i2c)

btn_nav = Pin(11, Pin.IN)
btn_sel = Pin(12, Pin.IN)
adc     = ADC(Pin(26))

# resistor values — change to match your circuit
R1      = 30000   # voltage divider high side
R2      = 10000   # voltage divider low side
R_shunt = 1.0     # shunt resistor for current
R_known = 10000   # known resistor for resistance measurement

modes  = ["Voltage", "Current", "Resistance", "Capacitance"]
units  = ["V", "A", "Ohm", "uF"]
cursor = 0

def read_value():
    raw  = adc.read_u16()
    vout = raw * 3.3 / 65535

    if cursor == 0:                          # voltage
        val = vout * (R1 + R2) / R2

    elif cursor == 1:                        # current
        val = vout / R_shunt

    elif cursor == 2:                        # resistance
        if vout >= 3.3:                      # avoid divide by zero
            val = 99999
        else:
            val = R_known * vout / (3.3 - vout)

    elif cursor == 3:                        # capacitance placeholder
        val = 0.0

    return round(val, 3)

def draw_option():
    oled.fill(0)
    oled.text("Select mode:", 0, 0, 1)
    oled.hline(0, 12, 128, 1)
    oled.text(modes[cursor], 20, 30, 1)
    oled.text(str(cursor+1)+"/"+str(len(modes)), 50, 52, 1)
    oled.show()

def draw_measuring():
    while btn_nav.value() == 1:
        val = read_value()

        oled.fill(0)
        oled.text("Measuring:", 0, 0, 1)
        oled.hline(0, 12, 128, 1)
        oled.text(modes[cursor], 0, 20, 1)
        oled.text(str(val) + " " + units[cursor], 0, 38, 1)
        oled.text("NAV = back", 0, 54, 1)
        oled.show()
        sleep(0.3)

# ── MAIN ──
draw_option()

last_nav = 1
last_sel = 1

while True:
    nav = btn_nav.value()
    sel = btn_sel.value()

    if last_nav == 1 and nav == 0:
        sleep(0.05)
        cursor = (cursor + 1) % len(modes)
        draw_option()

    if last_sel == 1 and sel == 0:
        sleep(0.05)
        draw_measuring()
        sleep(0.05)
        draw_option()

    last_nav = nav
    last_sel = sel
    sleep(0.01)