# The MIT License (MIT)
#
# Copyright (c) 2017 ladyada for Adafruit Industries
#
# 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
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`adafruit_sgp30`
====================================================
I2C driver for SGP30 Sensirion VoC sensor
* Author(s): ladyada
Implementation Notes
--------------------
**Hardware:**
* Adafruit `SGP30 Air Quality Sensor Breakout - VOC and eCO2
<https://www.adafruit.com/product/3709>`_ (Product ID: 3709)
**Software and Dependencies:**
* Adafruit CircuitPython firmware for the ESP8622 and M0-based boards:
https://github.com/adafruit/circuitpython/releases
* Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
"""
import time
from adafruit_bus_device.i2c_device import I2CDevice
from micropython import const
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_SGP30.git"
# pylint: disable=bad-whitespace
_SGP30_DEFAULT_I2C_ADDR = const(0x58)
_SGP30_FEATURESETS = (0x0020, 0x0022)
_SGP30_CRC8_POLYNOMIAL = const(0x31)
_SGP30_CRC8_INIT = const(0xFF)
_SGP30_WORD_LEN = const(2)
# pylint: enable=bad-whitespace
[docs]class Adafruit_SGP30:
"""
A driver for the SGP30 gas sensor.
"""
def __init__(self, i2c, address=_SGP30_DEFAULT_I2C_ADDR):
"""Initialize the sensor, get the serial # and verify that we found a proper SGP30"""
self._device = I2CDevice(i2c, address)
# get unique serial, its 48 bits so we store in an array
self.serial = self._i2c_read_words_from_cmd([0x36, 0x82], 0.01, 3)
# get featureset
featureset = self._i2c_read_words_from_cmd([0x20, 0x2f], 0.01, 1)
if featureset[0] not in _SGP30_FEATURESETS:
raise RuntimeError('SGP30 Not detected')
self.iaq_init()
@property
# pylint: disable=invalid-name
def TVOC(self):
"""Total Volatile Organic Compound in parts per billion."""
return self.iaq_measure()[1]
@property
# pylint: disable=invalid-name
def baseline_TVOC(self):
"""Total Volatile Organic Compound baseline value"""
return self.get_iaq_baseline()[1]
@property
# pylint: disable=invalid-name
def eCO2(self):
"""Carbon Dioxide Equivalent in parts per million"""
return self.iaq_measure()[0]
@property
# pylint: disable=invalid-name
def baseline_eCO2(self):
"""Carbon Dioxide Equivalent baseline value"""
return self.get_iaq_baseline()[0]
[docs] def iaq_init(self):
"""Initialize the IAQ algorithm"""
# name, command, signals, delay
self._run_profile(["iaq_init", [0x20, 0x03], 0, 0.01])
[docs] def iaq_measure(self):
"""Measure the eCO2 and TVOC"""
# name, command, signals, delay
return self._run_profile(["iaq_measure", [0x20, 0x08], 2, 0.05])
[docs] def get_iaq_baseline(self):
"""Retreive the IAQ algorithm baseline for eCO2 and TVOC"""
# name, command, signals, delay
return self._run_profile(["iaq_get_baseline", [0x20, 0x15], 2, 0.01])
[docs] def set_iaq_baseline(self, eCO2, TVOC): # pylint: disable=invalid-name
"""Set the previously recorded IAQ algorithm baseline for eCO2 and TVOC"""
if eCO2 == 0 and TVOC == 0:
raise RuntimeError('Invalid baseline')
buffer = []
for value in [TVOC, eCO2]:
arr = [value >> 8, value & 0xFF]
arr.append(self._generate_crc(arr))
buffer += arr
self._run_profile(["iaq_set_baseline", [0x20, 0x1e] + buffer, 0, 0.01])
[docs] def set_iaq_humidity(self, gramsPM3): # pylint: disable=invalid-name
"""Set the humidity in g/m3 for eCO2 and TVOC compensation algorithm"""
tmp = int(gramsPM3 * 256)
buffer = []
for value in [tmp]:
arr = [value >> 8, value & 0xFF]
arr.append(self._generate_crc(arr))
buffer += arr
self._run_profile(["iaq_set_humidity", [0x20, 0x61] + buffer, 0, 0.01])
# Low level command functions
def _run_profile(self, profile):
"""Run an SGP 'profile' which is a named command set"""
# pylint: disable=unused-variable
name, command, signals, delay = profile
# pylint: enable=unused-variable
#print("\trunning profile: %s, command %s, %d, delay %0.02f" %
# (name, ["0x%02x" % i for i in command], signals, delay))
return self._i2c_read_words_from_cmd(command, delay, signals)
def _i2c_read_words_from_cmd(self, command, delay, reply_size):
"""Run an SGP command query, get a reply and CRC results if necessary"""
with self._device:
self._device.write(bytes(command))
time.sleep(delay)
if not reply_size:
return None
crc_result = bytearray(reply_size * (_SGP30_WORD_LEN +1))
self._device.readinto(crc_result)
#print("\tRaw Read: ", crc_result)
result = []
for i in range(reply_size):
word = [crc_result[3*i], crc_result[3*i+1]]
crc = crc_result[3*i+2]
if self._generate_crc(word) != crc:
raise RuntimeError('CRC Error')
result.append(word[0] << 8 | word[1])
#print("\tOK Data: ", [hex(i) for i in result])
return result
# pylint: disable=no-self-use
def _generate_crc(self, data):
"""8-bit CRC algorithm for checking data"""
crc = _SGP30_CRC8_INIT
# calculates 8-Bit checksum with given polynomial
for byte in data:
crc ^= byte
for _ in range(8):
if crc & 0x80:
crc = (crc << 1) ^ _SGP30_CRC8_POLYNOMIAL
else:
crc <<= 1
return crc & 0xFF