import struct
from machine import UART, Pin
import time

# --- Configuration ---
UART_ID = 1  # Use UART 1 on Pico (GPIO 4/5 are UART1 TX/RX)
TX_PIN = 4
RX_PIN = 5
BAUD_RATE = 9600
# ---------------------

def read_pms_data(uart):
    """Reads a single, valid data packet from the PMS5003T sensor."""
    while True:
        # Read the start bytes (0x42, 0x4D)
        if uart.any():
            if uart.read(1) == b'\x42':
                if uart.read(1) == b'\x4d':
                    # Read the rest of the 30 bytes for a full 32-byte packet
                    data_bytes = uart.read(30)
                    if len(data_bytes) == 30:
                        # Unpack the data using the struct module
                        # >H: big-endian unsigned short (2 bytes)
                        # HHH: 3x PM mass conc. (CF=1)
                        # HHH: 3x PM mass conc. (Atmospheric environment)
                        # HHHHHH: 6x particle count (0.3um to 10um)
                        # HH: Reserved
                        # h: Temperature (signed short)
                        # h: Humidity (signed short)
                        # H: Checksum
                        unpacked_data = struct.unpack('>HHHHHHHHHHHHHhhH', data_bytes)

                        # Calculate checksum to verify data integrity
                        checksum = sum(b'\x42\x4d' + data_bytes[:-2])
                        if checksum == unpacked_data[-1]:
                            return {
                                "pm1_0_cf1": unpacked_data[0],
                                "pm2_5_cf1": unpacked_data[1],
                                "pm10_0_cf1": unpacked_data[2],
                                "pm1_0_atm": unpacked_data[3],
                                "pm2_5_atm": unpacked_data[4],
                                "pm10_0_atm": unpacked_data[5],
                                "pc_0_3um": unpacked_data[6],
                                "pc_0_5um": unpacked_data[7],
                                "pc_1_0um": unpacked_data[8],
                                "pc_2_5um": unpacked_data[9],
                                "pc_5_0um": unpacked_data[10],
                                "pc_10_0um": unpacked_data[11],
                                # Temperature is value / 10, Humidity is value / 10
                                "temperature_c": unpacked_data[13] / 10.0,
                                "humidity_percent": unpacked_data[14] / 10.0,
                            }
                        else:
                            print("Checksum failed. Discarding packet.")
                    else:
                        print(f"Incomplete packet received: {len(data_bytes)} bytes instead of 30.")
                else:
                    # Not a valid start, continue searching for 0x4D
                    continue
            else:
                # Not a valid start, continue searching for 0x42
                continue

# Initialize UART
uart = UART(UART_ID, baudrate=BAUD_RATE, tx=Pin(TX_PIN), rx=Pin(RX_PIN))
# Ensure sensor is awake by keeping SET pin high or floating (it floats high by default if not connected)

print("PMS5003T Sensor Reader Active. Waiting for data...")

try:
    while True:
        data = read_pms_data(uart)
        if data:
            print("-" * 25)
            print(f"PM1.0 (Env): {data['pm1_0_atm']} ug/m³")
            print(f"PM2.5 (Env): {data['pm2_5_atm']} ug/m³")
            print(f"PM10.0 (Env): {data['pm10_0_atm']} ug/m³")
            print(f"Temperature: {data['temperature_c']:.1f} °C")
            print(f"Humidity: {data['humidity_percent']:.1f} %")
            print("-" * 25)
        
        # The sensor outputs data every 200-800ms in active mode, 
        # so a small delay is sufficient to avoid buffer overflow
        time.sleep(1) 

except KeyboardInterrupt:
    print("Program terminated by user.")
except Exception as e:
    print(f"An error occurred: {e}")
finally:
    uart.deinit()