# Course : BUEL456C - Introduction to Raspberry Pi (VTU)
# Wokwi  : NTC Temperature Sensor on GP26 simulates LDR ADC
# Click the NTC sensor slider to change temperature and
# observe how the raw ADC value and voltage change

from machine import ADC, Pin
import math
import time

# ---- ADC setup on GP26 (NTC OUT pin) ------------------------
adc  = ADC(Pin(26))     # NTC analog output --> GP26 (ADC0)

# ---- NTC constants (Steinhart-Hart / Beta equation) ---------
BETA  = 3950            # NTC Beta coefficient
R_REF = 10000           # Reference resistor = 10 kOhm
R_NOM = 10000           # NTC nominal resistance at 25 C
T_NOM = 298.15          # 25 C in Kelvin

# ---- Classification thresholds (temperature based) ----------
HOT  = 35              # above this --> HOT
COLD = 15              # below this --> COLD

# ---- Convert raw ADC to temperature (Celsius) ---------------
def raw_to_temp(raw):
    if raw <= 0 or raw >= 65535:
        return None
    voltage    = raw * 3.3 / 65535
    resistance = R_REF * voltage / (3.3 - voltage)
    kelvin     = 1.0 / (math.log(resistance / R_NOM) / BETA
                        + 1.0 / T_NOM)
    return kelvin - 273.15

# ---- Classify temperature -----------------------------------
def classify(temp):
    if temp is None:  return "ERROR "
    if temp > HOT:    return "HOT   "
    if temp < COLD:   return "COLD  "
    return "NORMAL"

# ---- ASCII bar graph (0 C = empty, 50 C = full) -------------
def bar(temp):
    if temp is None: return "[" + "?" * 20 + "]"
    filled = int(max(0, min(20, (temp / 50) * 20)))
    return "[" + "#" * filled + " " * (20 - filled) + "]"

# ---- Main program -------------------------------------------
print("=" * 58)
print("   NTC Sensor + Pico ADC  |  BUEL456C  Wokwi")
print("   Click the NTC sensor to change temperature")
print("=" * 58)
print(f"  Cold < {COLD} C  |  Hot > {HOT} C")
print("-" * 58)

while True:
    raw  = adc.read_u16()
    volt = raw * 3.3 / 65535
    temp = raw_to_temp(raw)
    pct  = (raw / 65535) * 100

    if temp is not None:
        print(f"  Raw:{raw:6d} | {volt:.3f}V | "
              f"{pct:5.1f}% | {temp:6.2f}C | "
              f"{bar(temp)} | {classify(temp)}")
    time.sleep(1)