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gdev_i2c_Sensor_SCD30.py
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gdev_i2c_Sensor_SCD30.py
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#!/usr/bin/python3
# -*- coding: UTF-8 -*-
"""
I2C sensor module SCD30 for CO2 (by NDIR), Temperature, and Humidity
"""
###############################################################################
# This file is part of GeigerLog.
#
# GeigerLog is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# GeigerLog is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GeigerLog. If not, see <http://www.gnu.org/licenses/>.
###############################################################################
__author__ = "ullix"
__copyright__ = "Copyright 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024"
__credits__ = [""]
__license__ = "GPL3"
from gsup_utils import *
# Reference: Sensirion_CO2_Sensors_SCD30_Interface_Description.pdf - Version 0.91 – D1 – August 2018
# https://www.sensirion.com/de/umweltsensoren/kohlendioxidsensor/kohlendioxidsensoren-scd30/
#
# ATTENTION: SCD30 needs clock-stretching !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
#
# Clock-stretching is NOT available on Raspi!
# Work around is to reduce I2C clock in Raspi to 10 kHz (Default is 100 kHz)
# see: https://learn.adafruit.com/circuitpython-on-raspberrypi-linux/i2c-clock-stretching
#
# Maximal I2C speed is 100 kHz and the master has to support clock stretching. Sensirion recommends
# to operate the SCD30 at a baud rate of 50 kHz or smaller. Clock stretching period in write- and
# read-frames is 30 ms, however, due to internal calibration processes a maximal clock stretching
# of 150 ms may occur once per day. For detailed information to the I2C protocol, refer to NXP
# I2C-bus specification1. SCD30 does not support repeated start condition. Clock stretching is
# necessary to start the microcontroller and might occur before every ACK. I2C master clock
# stretching needs to be implemented according to the NXP specification. The boot-up time is < 2 s.
class SensorSCD30:
"""Code for the Sensirion SCD30 sensor"""
addr = 0x61 # the only option for the SCD30
name = "SCD30"
firmware = "not set" # my device: 3.66 (same as example from manual)
measIntvl = 5 # Measurement Interval in sec (default = 2)
frc = None # Forced Recalibration value (FRC). Default is 400 [ppm]
handle = g.I2CDongle # default for use by 'I2C' device; RaspiI2C defines its own
def __init__(self, addr, I2Chandle=None):
"""Init SensorSCD30 class"""
self.addr = addr
if I2Chandle is not None: self.handle = I2Chandle
def SensorInit(self):
"""Scan for presence, get Serial No, start periodic measurement"""
defname = "SensorInit: " + self.name + ": "
dmsg = "Sensor {:8s} at address 0x{:02X}".format(self.name, self.addr)
# dprint(defname)
setIndent(1)
## check for presence of an I2C device at I2C address
presence = self.handle.DongleIsSensorPresent(self.addr)
if not presence:
# no device found
setIndent(0)
return False, "Did not find any I2C device at address 0x{:02X}".format(self.addr)
else:
# device found
gdprint("Found an I2C device at address 0x{:02X}".format(self.addr))
# NOTE: Reset on the IOW dongle:
# When a reset is done, the first call of firmware after reset
# always results in a "wrong report ID" response, but the firmware
# does come out correct.
#
# Likewise, the first call to self.SCD30DataReady() also comes
# out with "wrong report ID" response, but this CANNOT be changed by
# removing reset!
#
## soft reset
# dprint(defname + "Sensor Reset")
# gdprint(self.SensorReset())
## get firmware version
# dprint(defname + "Get Firmware")
gdprint(self.SCD30getFirmwareVersion())
## get Forced Recalibration value (FRC)
# after power cycle this returns always "400" irrespective of what it really is!
# dprint(defname + "Get Forced Recalibration value (FRC)")
gdprint(defname + "Forced Recalibration value (FRC): {} ppm".format(self.SCD30getFRC()))
## set interval (default is 2 sec)
# dprint(defname + "Set Measurement Interval")
gdprint(self.SCD30MeasurementSetInterval(self.measIntvl))
## stop auto measurements # need to stop first???
# dprint(defname + "SCD30MeasurementStop")
gdprint(self.SCD30MeasurementStop())
## start auto measurements
# dprint(defname + "SCD30MeasurementStart")
gdprint(self.SCD30MeasurementStart())
setIndent(0)
return (True, "Initialized " + dmsg)
def SCD30getFirmwareVersion(self):
"""get the Firmware Version as Major.Minor"""
# 1.4.9 Read firmware version
# Command: 0xD100 , no argument needed
# Wait None in datasheet Version 1.0 – D1 – May 2020
# response: 3 bytes (2 b firmware + 1 bcrc) Firmware version: Major.Minor: 0x03, 0x42 => 3.66 (3.66 is also found on my chip)
# Duration:
# ISS: SCD30getFirmwareVersion: duration: 1.6 ms
start = time.time()
defname = "SCD30getFirmwareVersion: "
tmsg = "FirmWr"
register = 0xD100
readbytes = 3
data = []
wait = 0
answ = self.handle.DongleWriteRead (self.addr, register, readbytes, data, addrScheme=3, msg=tmsg, wait=wait)
if len(answ) != readbytes:
edprint(defname + "Failure reading Serial Number, reponse: ", answ)
return "Not Found"
self.firmware = "{}.{}".format(answ[0], answ[1])
duration = (time.time() - start) * 1000
msg = defname + "got firmware:{} (expecting: 3.66) in:{:0.1f} ms".format(self.firmware, duration)
return msg
def SensorReset(self):
"""Soft Reset SCD30 sensor"""
# 1.4.10 Soft reset
# The SCD30 provides a soft reset mechanism that forces the sensor into the same state as after
# powering up without the need for removing the power-supply. It does so by restarting its system
# controller. After soft reset the sensor will reload all calibrated data. However, it is worth
# noting that the sensor reloads calibration data prior to every measurement by default. This
# includes previously set reference values from ASC or FRC as well as temperature offset values
# last setting. The sensor is able to receive the command at any time, regardless of its internal
# state. In order to start the soft reset procedure the following command should be sent.
# duration: 0.7 ms
start = time.time()
# defname = "SensorReset: " + self.name + ": "
defname = "SensorReset: "
# dprint(defname)
tmsg = "Reset"
register = 0xD304
readbytes = 0
data = []
wrt = self.handle.DongleWriteReg(self.addr, register, readbytes, data, addrScheme=3, msg=tmsg)
# required wait 0.7 ms
time.sleep(0.001) # 1 ms
duration = 1000 * (time.time() - start)
return defname + "{} took {:0.1f} ms".format(tmsg, duration)
def SCD30MeasurementStart(self):
"""needs to be done only once"""
# 1.4.1 Trigger continuous measurement with optional ambient pressure compensation
# Starts continuous measurement of the SCD30 to measure CO 2 concentration, humidity
# and temperature. Measurement data which is not read from the sensor will be overwritten.
# The measurement interval is adjustable via the command documented in chapter 1.4.3,
# initial measurement rate is 2s.
# Continuous measurement status is saved in non-volatile memory. When the sensor is
# powered down while continuous measurement mode is active SCD30 will measure
# continuously after repowering without sending the measurement command. The CO2
# measurement value can be compensated for ambient pressure by feeding the pressure value
# in mBar to the sensor. Setting the ambient pressure will overwrite previous settings of
# altitude compensation. Setting the argument to zero will deactivate the ambient pressure
# compensation (default ambient pressure = 1013.25 mBar). For setting a new ambient pressure
# when continuous measurement is running the whole command has to be written to SCD30.
#
# command: 0x0010 argument
# argument: Format: uint16 Available range: 0 & [700 ... 1400]. Pressure in mBar.
# argument: 0x00 0x00 0x81 : Start continuous measurement without ambient pressure compensation
defname = "SCD30MeasurementStart: "
tmsg = "StartMeas"
register = 0x0010
readbytes = 0
data = [0x00, 0x00, 0x81]
wrt = self.handle.DongleWriteReg(self.addr, register, readbytes, data, addrScheme=3, msg=tmsg)
# return defname + "Done"
return "Measurement START Done"
def SCD30MeasurementStop(self):
"""needs to be done to stop activity"""
# 1.3.2 Stop continuous measurement
# Command: 0x0104, no argument (!!!!!!!!!!!!! in Example 0x0107 is used ????????????)
# ( but in 1.1.2 I2C Sequence there is again 0x0104 )
# response: None
defname = "SCD30MeasurementStop: "
tmsg = "StopMeas"
register = 0x0104
readbytes = 0
data = []
wrt = self.handle.DongleWriteReg(self.addr, register, readbytes, data, addrScheme=3, msg=tmsg)
# return defname + "Done"
return "Measurement STOP Done"
def SCD30MeasurementSetInterval(self, interval):
"""sets the measurement interval. Default is 2 sec"""
defname = "SCD30MeasurementSetInterval: "
# 1.3.3 Set measurement interval
# Sets the interval used by the SCD30 sensor to measure in continuous measurement mode (see chapter 1.3.1).
# Initial value is 2 s. The chosen measurement interval is saved in non-volatile memory and thus is not
# reset to its initial value after power up.
# Command: 0x4600 argument
# argument: Format: unit16 Interval in seconds. Available range: [2 ... 1800] given in 2 bytes
# in the order MSB, LSB, followed by CRC8
# Set measurement interval to 2s: 0x00, 0x02, 0xE3
# Set measurement interval to 5s: 0x00, 0x05, 0x74
# response: None
mi = interval
mi1 = mi >> 8
mi2 = mi & 0xFF
mi3 = getCRC8((mi1, mi2))
tmsg = "SetMeasIntvl"
register = 0x4600
readbytes = 0
# data = [0x00, 0x02, 0xE3] # default = 2 sec
data = [mi1, mi2, mi3] # my setting (5 sec = 0x00, 0x05, 0x74)
wrt = self.handle.DongleWriteReg(self.addr, register, readbytes, data, addrScheme=3, msg=tmsg)
return "Measurement Interval set to: {} sec".format(data[0]<<8 | data[1])
def SCD30getFRC(self):
"""Get the Forced Recalibration value (FRC). Default is 400 ppm"""
# 1.4.6 (De-)Activate Automatic Self-Calibration (ASC)
# Subsegment: Set Forced Recalibration value (FRC)
# Forced recalibration (FRC) is used to compensate for sensor drifts when a reference value of
# the CO 2 concentration in close proximity to the SCD30 is available. For best results, the
# sensor has to be run in a stable environment in continuous mode at a measurement rate of 2s
# for at least two minutes before applying the FRC command and sending the reference value.
# The reference CO2 concentration has to be within the range 400 ppm ≤ c ref (CO2 ) ≤ 2000 ppm.
# Command: 0x5204 argument
# argument: no argument for GETTING the FRC
# response: 3 bytes: FRC MSB, FRC LSB, CRC()
# Default 400ppm: 0x01, 0xc2, 0x50
defname = "SCD30getFRC: "
tmsg = "getFRC"
register = 0x5204
readbytes = 3
data = []
wait = 0
answ = self.handle.DongleWriteRead (self.addr, register, readbytes, data, addrScheme=3, msg=tmsg, wait=wait)
if len(answ) == readbytes: self.frc = answ[0] << 8 | answ[1]
return self.frc
def SCD30setFRC(self, frcvalue):
"""Set the Forced Recalibration value (FRC). Default is 400 ppm"""
# 1.4.6 (De-)Activate Automatic Self-Calibration (ASC)
# Subsegment: Set Forced Recalibration value (FRC)
# Forced recalibration (FRC) is used to compensate for sensor drifts when a reference value of
# the CO 2 concentration in close proximity to the SCD30 is available. For best results, the
# sensor has to be run in a stable environment in continuous mode at a measurement rate of 2s
# for at least two minutes before applying the FRC command and sending the reference value.
# The reference CO2 concentration has to be within the range 400 ppm ≤ c ref (CO2 ) ≤ 2000 ppm.
#
# The most recently used reference value is retained in **volatile** memory and can be read out
# with the command sequence given below. After repowering the sensor, the command will return
# the standard reference value of 400 ppm.
# NOTE: After a restart the reference is read as 400, however the applied reference
# remains in effect but cannot be read anymore
# Command: 0x5204 argument
# argument: SETTING the FRC: Format: uint16 CO2 concentration in ppm: FRC MSB, FRC LSB, CRC8
# Default 400ppm: 0x01, 0xc2, 0x50
# response: None (to read the current calib use SCD30getFRC())
#
defname = "SCD30setFRC: "
frc = int(frcvalue)
frc1 = frc >> 8
frc2 = frc & 0xFF
frc3 = getCRC8((frc1, frc2))
tmsg = "setFRC"
register = 0x5204
readbytes = 0
data = [frc1, frc2, frc3]
wrt = self.handle.DongleWriteReg(self.addr, register, readbytes, data, addrScheme=3, msg=tmsg)
self.frc = self.SCD30getFRC()
return defname + "Done"
def SCD30DataReady(self):
"""get the data-ready status of sensor;
return: 1 True Data are ready
0 False Data are NOT ready
-1 Improper response
"""
# 1.4.4 Get data ready status
# Data ready command is used to determine if a measurement can be read from the sensor’s
# buffer. Whenever there is a measurement available from the internal buffer this command
# returns 1 and 0 otherwise. As soon as the measurement has been read by the return value
# changes to 0. Note that the read header should be send with a delay of > 3ms following
# the write sequence.
# It is recommended to use data ready status byte before readout of the measurement values.
#
# command: 0x0202, no argument needed
# readbytes: 3; MSB, LSB, CRC
start = time.time()
defname = "SCD30DataReady: "
# dprint(defname)
try:
ready = -1 # code for failure
tmsg = "Ready?"
msg = ""
register = 0x0202
readbytes = 3
data = []
wait = 0.003 # wait 3 ms acc to datasheet: Version 1.0 – D1 – May 2020
answ = self.handle.DongleWriteRead (self.addr, register, readbytes, data, addrScheme=3, msg=tmsg, wait=wait)
duration = (time.time() - start) * 1000
if len(answ) == readbytes:
word0 = answ[0] << 8 | answ[1]
if word0 == 1:
ready = True # Data are ready
msg = "30 Data ready"
color = BOLDGREEN
else:
ready = False # Data are NOT ready
msg = "30 Data NOT ready"
color = BOLDRED
msg = defname + " "*70 + "{}{}".format(color, msg)
elif len(answ) == 0:
msg = BOLDRED + "30 No data returned: answ= '{}'".format(answ)
else:
msg = BOLDRED + "30 Improper data returned: answ= '{}'".format(answ)
cdprint(msg + " {:0.1f} ms".format(duration))
except Exception as e:
exceptPrint(e, defname)
return ready
def SensorgetValues(self):
"""Read the CO2, Temp and Humid values if available"""
# 1.4.5 Read measurement
# When new measurement data is available it can be read out with the following command.
# Note that the read header should be send with a delay of > 3ms following the write
# sequence. Make sure that the measurement is completed by reading the data ready status
# bit before read out.
#
# Command: 0x0300, no argument needed. Reads a single measurement of CO2 concentration. (But also the rest!)
# Example with sensor returning: CO2 Concentration = 439 PPM
# Humidity = 48.8 %
# Temperature = 27.2 °C
# CO2 CO2 CO2 CO2 T T T T RH RH RH RH
# MMSB MLSB CRC LMSB LLSB CRC MMSB MLSB CRC LMSB LLSB CRC MMSB MLSB CRC LMSB LLSB CRC
# 0x43 0xDB 0xCB 0x8c 0x2e 0x8f 0x41 0xd9 0x70 0xe7 0xff 0xf5 0x42 0x43 0xbf 0x3a 0x1b 0x74
# Example: The CO2 concentration 400 ppm corresponds to 0x43c80000 in Big-Endian notation.
# measurement duration:
# mit dongle ISS: SCD30: CO2:600.779, Temp:22.575, Humid:33.948 dur: 4.9 ... 5.7 ms (avg: 5.2) 1.0x
# mit dongle ELV: SCD30: CO2:773.918, Temp:27.040, Humid:36.856 dur: 14.5 ... 17.8 ms (avg: 14.8 ms) 2.8x
# mit dongle IOW: SCD30: CO2:807.496, Temp:26.786, Humid:37.331 dur: 47 ... 51 ms (avg: 47.9 ms) 9.2x
# mit dongle FTD: SCD30: CO2:807.496, Temp:26.786, Humid:37.331 dur: xx ... xx ms (avg: xxxx ms) xxxx
# mit dongle ISS: 100 kHz SCD30: dur: 4.9 ... 5.7 ms (avg: 5.2) 1.0x
# mit dongle ISS: 400 kHz SCD30: dur: 3.1 ... 4.2 ms (avg: 3.4) 0.65x 1.53x faster
# @9600 baud
# mit dongle ISS: 100 kHz SCD30: dur: 10.8 ... 12.6 ms (avg: 11.6)
# mit dongle ISS: 400 kHz SCD30: dur: 8.8 ... 10.0 ms (avg: 9.1)
# mit dongle ISS: 1000 kHz SCD30: dur: 8.4 ... 11.1 ms (avg: 9.3) # slower!
start = time.time()
defname = "SensorgetValues: " + self.name + ": "
sgvdata = (g.NAN,) * 3
# cdprint(defname)
setIndent(1)
### does not help
# start = time.time()
# success = False
# while (time.time() - start) < 1:
# time.sleep(0.02)
# dataReady = self.SCD30DataReady()
# if dataReady:
# success = True
# break
# if not success: rdprint(defname, "Giving up")
###
dataReady = self.SCD30DataReady()
if dataReady == 1:
# data are ready
tmsg = "getval"
register = 0x0300
readbytes = 18
data = []
wait = 0.003 # wait 3 ms acc to datasheet: Version 1.0 – D1 – May 2020
answ = self.handle.DongleWriteRead (self.addr, register, readbytes, data, addrScheme=3, msg=tmsg, wait=wait)
#####################################################################################################################
# reference --> CO2 Concentration = 439 PPM, Temperature = 27.2 °C, Humidity = 48.8 %
# answ = [0x43, 0xDB, 0xCB, 0x8c, 0x2e, 0x8f, 0x41, 0xd9, 0x70, 0xe7, 0xff, 0xf5, 0x42, 0x43, 0xbf, 0x3a, 0x1b, 0x74]
#####################################################################################################################
if len(answ) == readbytes:
# Big-Endian notation
# must convert to float explicitely, because numpy data format creates blobs in the SQL database!
data_bytes = np.array(answ[0:2] + answ[3:5], dtype=np.uint8)
co2 = float(data_bytes.view(dtype='>f')[0])
data_bytes = np.array(answ[6:8] + answ[9:11], dtype=np.uint8)
temp = float(data_bytes.view(dtype='>f')[0])
data_bytes = np.array(answ[12:14] + answ[15:17], dtype=np.uint8)
humid = float(data_bytes.view(dtype='>f')[0])
if co2 > 300: sgvdata = (round(co2, 0), round(temp, 3), round(humid, 3)) # first value is most often CO2==0; should be >400, but give it room
msg = True, defname + "CO2:{:6.3f}, Temp:{:6.3f}, Humid:{:6.3f}".format(co2, temp, humid)
else:
msg = False, defname + "Failure reading proper byte count"
else:
# data not ready
msg = False, defname + "Data NOT ready, or failure to get status, or wrong bytecount"
duration = (time.time() - start) * 1000
if msg[0]: gdprint(msg[1] + " dur:{:0.2f} ms".format(duration))
setIndent(0)
return sgvdata
def SensorGetInfo(self):
info = "{}\n" .format("CO2, Temperature, Humidity")
info += "- Address: 0x{:02X}\n" .format(self.addr)
info += "- Firmware: {}\n" .format(self.firmware)
info += "- Measure Intvl: {} sec\n" .format(self.measIntvl)
info += "- Ref. Value: {} ppm\n" .format(self.frc)
info += "- Variables: {}\n" .format(", ".join("{}".format(x) for x in g.Sensors["SCD30"][5]))
return info.split("\n")