88 lines
2.1 KiB
Python
88 lines
2.1 KiB
Python
'''
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Script to get CO2 values
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need parameter: CO2_port
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/usr/bin/python3 /var/www/moduleair_pro_4g/MH-Z19/get_data.py ttyAMA4
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'''
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import serial
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import requests
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import json
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import sys
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import subprocess
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import time
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parameter = sys.argv[1:] # Exclude the script name
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#print("Parameters received:")
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port='/dev/'+parameter[0]
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ser = serial.Serial(
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port=port,
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baudrate=9600,
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parity=serial.PARITY_NONE,
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stopbits=serial.STOPBITS_ONE,
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bytesize=serial.EIGHTBITS,
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timeout = 1
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)
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# Command to read CO2 concentration
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# Contains 9 bytes (byte 0 ~ 8)
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# FIRST byte: fixed to 0xFF
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# SECOND byte: sensor number (factory default is 0 x01)
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# THIRD byte: 0x86 Gas Concentration
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# end with proof test value Checksum
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READ_CO2_COMMAND = b'\xFF\x01\x86\x00\x00\x00\x00\x00\x79'
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def read_co2():
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# Send the read command to the MH-Z19
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ser.write(READ_CO2_COMMAND)
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# Wait for the response from the sensor
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time.sleep(2) # Wait for the sensor to respond
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# Read the response from the sensor (9 bytes expected)
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response = ser.read(9)
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# Print the response to debug
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# print(f"Response: {response}")
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# Check if the response is valid (the first byte should be 0xFF)
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if len(response) < 9:
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print("Error: No data or incomplete data received.")
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return None
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if response[0] == 0xFF:
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# Extract the CO2 concentration value (byte 2 and 3)
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co2_concentration = response[2] * 256 + response[3]
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return co2_concentration
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else:
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print("Error reading data from sensor.")
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return None
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def main():
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try:
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co2 = read_co2()
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if co2 is not None:
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# Create a dictionary to store the data
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data = {
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"CO2": co2
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}
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# Convert the dictionary to a JSON string
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json_data = json.dumps(data)
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print(json_data) # Output the JSON string
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else:
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print("Failed to get CO2 data.")
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except KeyboardInterrupt:
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print("Program terminated.")
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finally:
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ser.close()
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if __name__ == '__main__':
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main()
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