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d6f_ph.py
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d6f_ph.py
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#coding:utf-8
#
# (c) 2023 ekspla.
# MIT license. https://github.com/ekspla/D6F-PH
"""A micropython module for differential pressure sensor, D6F-PH (OMRON).
"""
from time import sleep_ms
class D6F_PH:
"""
I2C driver for D6F-PH pressure sensor (OMRON)
"""
_I2C_ADDRESS = 0x6c
# Specific Model of D6F-PH
# e.g. for model 5050
# Where:
# the pressure range is from -500 to +500 Pa
_PRESSURE_RANGE = {
'0505': 100, # +/- 50 Pa
'0025': 250, # 0-250 Pa
'5050': 1000, # +/- 500 Pa
}
# Pressure transfer function per Datasheet
def _PRESSURE_MODE_P(self, output_decimal):
return (output_decimal - 1024) * self._pres_range / 60000
def _PRESSURE_MODE_PN(self, output_decimal):
return (output_decimal - 1024) * self._pres_range / 60000 - self._pres_range / 2
# Temperature transfer function per Datasheet
@staticmethod
def _temp_celsius(output_decimal):
return (output_decimal - 10214) * 100 / 3739 # // convert to degree-C
def __init__(self, i2c_obj, address=_I2C_ADDRESS, pressure_range='5050', en_crc=False, offset=0):
"""
:param i2c_obj: I2C class; I2C bus
:param address: int; Sensor I2C address, pls refer to the datasheet
:param pressure_range: int or str; Sensor pressure range, pls refer to the datasheet
:param en_crc: True/False; enable/disable crc8 for data validation
:param offset: int; pressure offset in raw decimal
"""
self._i2c = i2c_obj
self._addr = address
if isinstance(pressure_range, str):
self._pres_range = self._get_pres_range(pressure_range)
else:
self._pres_range = pressure_range
self._pres_func = self._get_pres_func(self._pres_range)
self._offset = offset
self._i2c.writeto(address, b'\x0b\x00') # /* EEPROM Control <= 00h */
if en_crc:
self.en_crc = True
self._i2c.writeto(address, b'\x00\xd0\x49\x18\x02') # /* [D049] <= 02h */
self._buffer = bytearray(3) # 2-byte data and 1-byte crc
else:
self.en_crc = False
self._buffer = bytearray(2) # 2-byte data
def _get_pres_func(self, pres_range):
if isinstance(pres_range, int):
if pres_range == 250:
func = '_PRESSURE_MODE_P'
elif pres_range in (100, 1000):
func = '_PRESSURE_MODE_PN'
return getattr(self, func)
else:
raise Exception('Error: Incorrect pressure range.')
def _get_pres_range(self, pressure_range):
if isinstance(pressure_range, str):
if pressure_range in self._PRESSURE_RANGE:
return self._PRESSURE_RANGE.get(pressure_range)
else:
raise Exception('Error: Incorrect pressure range setting.')
def crc8(self, byte_array, poly=0x131, init=0x00): # Polynomial: x^8 + x^5 + x^4 + x^0
"""
Calculate CRC8-Dallas/Maxim
:param byte_array: bytes or bytearray; sensor data
:return: int; crc8
"""
crc = init
for byte in byte_array:
crc ^= byte
for _ in range(8):
crc = (crc << 1) ^ poly if crc & 0x80 else crc << 1
crc &= 0xff
return crc ^ 0x00
def read_raw(self):
"""
Read raw decimal output
:return: tuple(int, int); raw pressure decimal output, raw temperature decimal output
"""
self._i2c.writeto(self._addr, b'\x00\xd0\x40\x18\x06') # /* [D040] <= 06h */
sleep_ms(33)
self._i2c.writeto(self._addr, b'\x00\xd0\x51\x2c') # /* [D051/D052] => Read COMP_DATA1_H/COMP_DATA1_L values */
self._i2c.readfrom_mem_into(self._addr, 0x07, self._buffer)
#print(self._buffer)
if self.en_crc and ((crc := self.crc8(self._buffer[:2])) != self._buffer[2]):
print(self._buffer, hex(crc))
return None
raw_pres = int.from_bytes(self._buffer[:2], 'big') - self._offset # Covert from 2-byte BE unsigned int.
self._i2c.writeto(self._addr, b'\x00\xd0\x61\x2c') # /* [D061/D062] => Read TMP_H/TMP_L values */
self._i2c.readfrom_mem_into(self._addr, 0x07, self._buffer)
#print(self._buffer)
if self.en_crc and ((crc := self.crc8(self._buffer[:2])) != self._buffer[2]):
print(self._buffer, hex(crc))
return None
raw_temp = int.from_bytes(self._buffer[:2],'big') # Covert from 2-byte BE unsigned int.
return raw_pres, raw_temp
def read(self):
"""
Read pressure in Pa & temperature in degree Celsius
:return: tuple(float, float); pressure reading in Pa, temperature reading in degree Celsius
"""
if not (raw_counts := self.read_raw()):
return None
raw_pres, raw_temp = raw_counts
temp = self._temp_celsius(raw_temp)
pres = self._pres_func(raw_pres)
return pres, temp
def read_pa(self):
"""
Read pressure in Pa
:return: float;
"""
pa, _ = self.read()
return pa
def read_psi(self):
"""
Read pressure in PSI
:return: float;
"""
return self.read_pa() / 6894.75729
def read_hpa(self):
"""
Read pressure in hPa
:return: float;
"""
return self.read_pa() / 100
def read_temp_c(self):
"""
Read temperature in degree Celsius
:return: float;
"""
_, temp = self.read()
return temp
def read_temp_f(self):
"""
Read temperature in Fahrenheit
:return: float
"""
return self.read_temp_c() * 1.8 + 32