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ags10.py
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ags10.py
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# MIT License
#
# Copyright (c) 2023 Gavesha Labs
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import time
""" AGS10 module """
class AGS10:
AGS10_I2CADDR_DEFAULT = 0x1A # Default I2C address
def __init__(self, i2c, address=AGS10_I2CADDR_DEFAULT):
self._i2c = i2c
self._address = address
self._dbuf = bytearray(5)
self._rbuf = bytearray(5)
self._dbuf_read_time = 0
self._rbuf_read_time = 0
self._init_time = time.time()
self._validate=False
@property
def status(self):
# The status byte read from the sensor, see datasheet for details
self._read_to_dbuf()
return self._dbuf[0]
@property
def is_ready(self):
return not (self.status & 0x01)
@property
def total_volatile_organic_compounds_ppb(self):
self._read_to_dbuf()
if self._validate and self._calc_crc8(self._dbuf[0:4]) != self._dbuf[4]:
raise AssertionError('crc mistmatched')
return int.from_bytes(self._dbuf[1:4], 'big')
@property
def resistance_kohm(self):
self._read_to_rbuf()
if self._validate and self._calc_crc8(self._rbuf[0:4]) != self._rbuf[4]:
raise AssertionError('crc mistmatched')
return int.from_bytes(self._rbuf[0:4], 'big') * 0.1
@property
def version(self):
buf = bytearray(5)
self._i2c.readfrom_mem_into(self._address, 0x11, buf)
return buf[3]
@property
def check_crc(self):
return self._validate
@check_crc.setter
def check_crc(self, value):
self._validate = value
def zero_point_calibrate(self, kohm):
data_bytes = int.to_bytes(int(kohm / 0.1), 2, 'big')
buf = [0, 0x0C, data_bytes[0], data_bytes[1]]
crc = self._calc_crc8(buf)
buf = [0, 0x0C, data_bytes[0], data_bytes[1], crc]
self._i2c.writeto_mem(self._address, 0x01, bytearray(buf))
def zero_point_factory_reset(self):
buf = [0, 0x0C, 0xFF, 0xFF, 0x81]
self._i2c.writeto_mem(self._address, 0x01, bytearray(buf))
def update_address(self, new_addr):
new_addr_inv = ~new_addr
buf = [new_addr, new_addr_inv, new_addr, new_addr_inv]
crc = self._calc_crc8(buf)
buf = [new_addr, new_addr_inv, new_addr, new_addr_inv, crc]
self._i2c.writeto_mem(self._address, 0x21, bytearray(buf))
""" Private functions """
def _read_to_dbuf(self):
if time.time() - self._dbuf_read_time < 2:
# min 1.5s delay is required between successive data acquisitions
return
# Read sensor data to buffer
self._i2c.readfrom_into(self._address, self._dbuf, True)
self._dbuf_read_time = time.time()
def _read_to_rbuf(self):
if time.time() - self._rbuf_read_time < 2:
# min 1.5s delay is required between successive resistance reads
return
# Read sensor data to buffer
self._i2c.readfrom_mem_into(self._address, 0x20, self._rbuf)
self._rbuf_read_time = time.time()
def _calc_crc8(self, data):
crc=0xFF
for byte in data :
crc^=byte
for i in range(8) :
crc=((crc<<1)^0x31) if crc & 0x80 else crc<<1
return crc&0xFF