simple pyserial script to send commands encoded as weather data over LoRa

lora_weather_encoder.py

import serial
import time

# Configure the serial port.
# Replace '/dev/ttyUSB0' with your actual port:
# Windows: 'COM3', 'COM4', etc.
# Mac/Linux: '/dev/ttyUSB0', '/dev/ttyAMA0', etc.
SERIAL_PORT = '/dev/ttyS4'
BAUD_RATE = 115200
target_addr = 10
local_addr = 12
network_id = 18
network_band = 915000000

try:
    ser = serial.Serial(
        port=SERIAL_PORT,
        baudrate=BAUD_RATE,
        bytesize=serial.EIGHTBITS,
        parity=serial.PARITY_NONE,
        stopbits=serial.STOPBITS_ONE,
        timeout=1.0
    )
except Exception as e:
    print(f"Error opening serial port: {e}")
    exit()


# Simple mapping dictionary to encode hex characters into plausible weather metrics.
# We will use the decimals of different weather readings to encode our payload data.
HEX_MAP = {
    '0': (15.1, 45.1), '1': (15.2, 45.2), '2': (15.3, 45.3), '3': (15.4, 45.4),
    '4': (15.5, 45.5), '5': (15.6, 45.6), '6': (15.7, 45.7), '7': (15.8, 45.8),
    '8': (16.1, 46.1), '9': (16.2, 46.2), 'a': (16.3, 46.3), 'b': (16.4, 46.4),
    'c': (16.5, 46.5), 'd': (16.6, 46.6), 'e': (16.7, 46.7), 'f': (16.8, 46.8)
}

# Reverse mapping for decoding
REV_MAP_TEMP = {v[0]: k for k, v in HEX_MAP.items()}
REV_MAP_HUMID = {v[1]: k for k, v in HEX_MAP.items()}


def encode_to_weather(hex_payload):
    """
    Encodes a hexadecimal payload string into a series of mock weather telemetry packets.
    For demonstration, each hex character pair is mapped to simulated Temp (T) and Humidity (H) decimals.
    """
    encoded_packets = []
    # Ensure lowercase hex
    clean_hex = hex_payload.lower().strip()

    # Process the hex string in pairs
    for i in range(0, len(clean_hex), 2):
        char1 = clean_hex[i]
        char2 = clean_hex[i + 1] if i + 1 < len(clean_hex) else '0'

        t_val = HEX_MAP.get(char1, (15.0, 45.0))[0]
        h_val = HEX_MAP.get(char2, (15.0, 45.0))[1]

        # Format the fake weather string
        fake_packet = f"ID:WS915;T:{t_val}C;H:{h_val}%;P:1013.2hPa;W:2.4m/s"
        encoded_packets.append(fake_packet)

    return encoded_packets

def send_command(command_str):
    """Formats and sends an AT command to the module."""
    full_command = f"{command_str}\r\n"
    ser.write(full_command.encode('utf-8'))
    print(f"[Sent]: {command_str}")


# Basic initialization sequence
time.sleep(1)
send_command("AT")  # Test if the module responds with "+OK"
time.sleep(2)
send_command(f"AT+ADDRESS={local_addr}") #  Set Address
time.sleep(2)
send_command(f"AT+NETWORKID={network_id}") #  Set Network
time.sleep(2)
send_command(f"AT+BAND={network_band}") #  Set Band
time.sleep(2)

# Example Usage
if __name__ == "__main__":
    # Simulated command to send: "CMD: RUN WHOAMI" converted to hex
    original_data = "CMD: WHOAMI"
    hex_data = original_data.encode('utf-8').hex()

    print(f"Original String: {original_data}")
    print(f"Hex Representation: {hex_data}\n")

    # Encode payload as benign weather data
    weather_packets = encode_to_weather(hex_data)
    print("--- Transmitted Weather Packets ---")
    time.sleep(1)
    start_msg = f"START:{len(weather_packets)}"
    len_start_msg = len(start_msg)
    send_command(f"AT+SEND={target_addr},{len_start_msg},{start_msg}")
    time.sleep(1)
    for pkt in weather_packets:
        length = len(pkt)
        send_command(f"AT+SEND={target_addr},{length},{pkt}")
        time.sleep(1)
    send_command(f"AT+SEND={target_addr},3,END")