121 lines
4.8 KiB
Python
121 lines
4.8 KiB
Python
import minimalmodbus
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import serial
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import time
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class Sensor():
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# MODBUS constants
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holding_register_start = 40001
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holding_register_end = 49999
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input_register_start = 30001
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input_register_end = 39999
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# Sensor specific config
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baudrates = [ 4800,9600,14400,19200,28800,38400,57600,76800,115200 ] # allowed baudrates
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input_registers = { \
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'CO2': 30010, \
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'T_SHT4x': 30011, \
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'RH_SHT4x': 30012, \
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'T_SCD4x': 30013, \
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'RH_SCD4x': 30014, \
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'T_SHT4x_signed': 30015, \
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'T_SCD4x_signed': 30016 }
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holding_registers = { \
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'LED_on': 40001, \
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'LED_brightness': 40002, \
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'LED_smooth': 40003, \
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'CO2_alert_limit_1': 40004, \
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'CO2_alert_limit_2': 40005, \
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'SCD4x_temperature_offset': 40006, \
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'MODBUS_address': 40007, \
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'baudrate': 40008 }
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# readout and error counters
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readout_total = 0
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readout_error_invalid_response = 0 # checksum error: bus transmission corrupted?
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readout_error_no_response = 0 # no response - sensor device was busy
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# methods
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def __init__(self, address=247, baudrate=19200, dev_file='/dev/rs485'):
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self.dev_file = dev_file
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self.address = address
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self.baudrate = baudrate
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self.open()
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def open(self):
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self.serial = minimalmodbus.Instrument(self.dev_file, self.address, close_port_after_each_call=True)
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self.serial.serial.baudrate = self.baudrate
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self.serial.serial.bytesize = 8
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self.serial.serial.parity = serial.PARITY_EVEN
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self.serial.serial.stopbits = 1
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self.serial.serial.timeout = 0.05 # seconds
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self.serial.mode = minimalmodbus.MODE_RTU # rtu or ascii mode
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self.serial.clear_buffers_before_each_transaction = True
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def close(self):
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self.serial.serial.close()
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self.serial = None
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# High level read functions
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@property
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def CO2(self):
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return int(self.read_register(self.input_registers['CO2']))
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@property
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def T(self):
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# TODO maybe use rather signed version?
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return self.T_SHT4x
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@property
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def RH(self):
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return self.RH_SHT4x
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@property
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def T_SHT4x(self):
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return self.read_register(self.input_registers['T_SHT4x']) / 10
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@property
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def T_SHT4x_signed(self):
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return self.read_register(self.input_registers['T_SHT4x_signed'], signed=True) / 10
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@property
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def RH_SHT4x(self):
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return self.read_register(self.input_registers['RH_SHT4x'])
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@property
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def T_SCD4x(self):
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return self.read_register(self.input_registers['T_SCD4x']) / 10
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@property
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def T_SCD4x_signed(self):
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return self.read_register(self.input_register['T_SCD4x_signed'], signed=True) / 10
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@property
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def RH_SCD4x(self):
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return self.read_register(self.input_registers['RH_SCD4x'])
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# generic read register function
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def read_register(self, register_number, retries=10):
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if self.input_register_start <= register_number <= self.input_register_end:
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function_code = 4
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register_offset = register_number - self.input_register_start
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elif self.holding_register_start <= register_number <= self.holding_register_end:
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function_code = 3
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register_offset = register_number - self.holding_register_start
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else:
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# wrong register number
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raise ValueError
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while retries:
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retries -= 1
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try:
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self.readout_total += 1
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# minimalmodbus divides received register value by 10
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return self.serial.read_register(register_offset, 1, functioncode=function_code) * 10
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except minimalmodbus.NoResponseError as e:
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last_exception = e
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self.readout_error_no_response += 1
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continue
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except minimalmodbus.InvalidResponseError as e:
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last_exception = e
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self.readout_error_invalid_response += 1
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continue
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# retries failed, raise last exception to inform user
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raise last_exception
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# generic write register function
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def write_register(self, register_number, register_value, retries=10):
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if not self.holding_register_start <= register_number <= self.holding_register_end:
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raise ValueError
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register_offset = register_number - self.holding_register_start
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while retries:
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retries -= 1
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try:
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return self.serial.write_register(register_offset, register_value, functioncode=6)
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except (minimalmodbus.NoResponseError, minimalmodbus.InvalidResponseError) as e:
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last_exception = e
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continue
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raise last_exception
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