CCS811空氣品質感測器

感測器簡介

CCS-811是一種超低功耗的數位氣體感測器，集成了CCS801感測器和8位MCU(帶模數轉換器(ADC))，用來檢測室內的空氣品質，包括二氧化碳(CO2)和廣泛的揮發性有機化合物氣體(VOCs)。

電路圖

程式列表

Python - CCS811.py

from micropython import const

from machine import I2C, Pin

class GasSensor:

READ_DELAY = 10000

CCS811_HW_ID_CODE = 0x81

CCS811_REF_RESISTOR = 100000.0

# default address

CCS811_ADDR = const(0x5A)

# Commands

CCS811_STATUS = const(0x00)

CCS811_MEAS_MODE = const(0x01)

CCS811_ALG_RESULT_DATA = const(0x02)

CCS811_RAW_DATA = const(0x03)

CCS811_ENV_DATA = const(0x05)

CCS811_NTC = const(0x06)

CCS811_THRESHOLDS = const(0x10)

CCS811_BASELINE = const(0x11)

CCS811_HW_ID = const(0x20)

CCS811_HW_VERSION = const(0x21)

CCS811_FW_BOOT_VERSION = const(0x23)

CCS811_FW_APP_VERSION = const(0x24)

CCS811_ERROR_ID = const(0xE0)

CCS811_APP_START = const(0xF4)

CCS811_SW_RESET = const(0xFF)

def __init__(self, i2c, address = CCS811_ADDR):

self.i2c = i2c

self.address = address

self.tempOffset = 0

self.temp =0

self.configure_ccs811()

def configure_ccs811(self):

# See figure 22 in datasheet: Bootloader Register Map

# Check HW_ID register (0x20) - correct value 0x81

hardware_id = bytearray(1)

cmd = self.CCS811_HW_ID

self.i2c.send(cmd,self.address)

self.i2c.recv(hardware_id,self.address)

if (hardware_id[0] != self.CCS811_HW_ID_CODE):

raise ValueError('Wrong Hardware ID.')

# Check Status Register (0x00) to see if valid application present-

status = bytearray(1)

cmd = self.CCS811_STATUS

self.i2c.send(cmd, self.address)

self.i2c.recv(status,self.address)

# See figure 12 in datasheet: Status register: Bit 4: App valid

if not (status[0] >> 4) & 0x01:

raise ValueError('Application not valid.')

self.tempOffset = self.calculateTemperature() - 25.0

cmd = self.CCS811_APP_START

# Application start. Write with no data to App_Start (0xF4)

self.i2c.send(cmd,self.address)

# Set drive mode 1 - see Figure 13 in datasheet: Measure Mode Register (0x01)

cmd = bytearray([0x01, 0x18])

self.i2c.send(cmd,self.address)

def print_error(self):

"""Error code. """

error = bytearray(1)

cmd = self.CCS811_ERROR_ID

self.i2c.send(cmd,self.address)

self.i2c.recv(error,self.address)

message = 'Error: '

if (error[0] >> 5) & 1:

message += 'HeaterSupply '

elif (error[0] >> 4) & 1:

message += 'HeaterFault '

elif (error[0] >> 3) & 1:

message += 'MaxResistance '

elif (error[0] >> 2) & 1:

message += 'MeasModeInvalid '

elif (error[0] >> 1) & 1:

message += 'ReadRegInvalid '

elif (error[0] >> 0) & 1:

message += 'MsgInvalid '

else :

return False

print(message)

return True

def available(self):

status = bytearray(1)

cmd = self.CCS811_STATUS

self.i2c.send(cmd,self.address)

self.i2c.recv(status,self.address)

return status[0]

def ReadData(self):

""" Equivalent Carbone Dioxide in parts per millions. Clipped to 400 to 8192ppm."""

""" Total Volatile Organic Compound in parts per billion. """

buf = bytearray(8)

cmd = self.CCS811_ALG_RESULT_DATA

self.i2c.send(cmd,self.address)

self.i2c.recv(buf,self.address)

self.eCO2 = (buf[0] << 8) | (buf[1])

self.TVOC = (buf[2] << 8) | (buf[3])

# print("Data: ")

# print("".join("\\x%02x" % i for i in buf))

def calculateTemperature(self):

buf = bytearray(4)

cmd = self.CCS811_NTC

self.i2c.send(cmd,self.address)

self.i2c.recv(buf,self.address)

vref = (buf[0] << 8) | buf[1]

vntc = (buf[2] << 8) | buf[3]

# from ams ccs811 app note

ntc_temp = 0

if vref>0 :

rntc = vntc * self.CCS811_REF_RESISTOR / vref

ntc_temp = (rntc / self.CCS811_REF_RESISTOR) # 1

ntc_temp /= 3380 # 2

ntc_temp += 1.0 / (25 + 273.15) # 3

ntc_temp = 1.0 / ntc_temp # 4

ntc_temp -= 273.15 # 5

ntc_temp -= self.tempOffset

return ntc_temp

def reset(self):

""" Initiate a software reset. """

seq = bytearray([self.CCS811_SW_RESET, 0x11, 0xE5, 0x72, 0x8A])

self.i2c.send(seq,self.address)

Python - ePy-Lite_CCS811.py

"""

ePy-Lite_CCS811.py

ePy-Lite Sensor

-----------------

3V3 VCC

GND GND

P17_SCL0 SCL

P18_SDA0 SDA

GND WAK

INT

RST

ADD

"""

from machine import I2C, Pin

from machine import Switch #Get button KEY library

import utime

from CCS811 import GasSensor

# Start Function

if __name__=="__main__":

KeyA = Switch('keya') #Create button A

sensor_i2c = I2C(0,I2C.MASTER,baudrate=100000) #Create I2C0 Master Mode, Baudrate=100kHz

gas_sensor = GasSensor(sensor_i2c, address=GasSensor.CCS811_ADDR)

print('Starting CCS811 Read')

utime.sleep(5)

while True:

if not (gas_sensor.available() >> 4) & 0x01:

print('STATUS: 0x%2X' %(status[0]))

print('Application not valid.')

gas_sensor.print_error()

else :

temp = gas_sensor.calculateTemperature()

gas_sensor.ReadData()

print('{} - eCO2: {} ppm, TVOC: {} ppb, Temp: {} C'.format(gas_sensor_id, gas_sensor.eCO2, gas_sensor.TVOC, temp))

if KeyA.value() == True: #Press A Key

break

utime.sleep_ms(1000)

sensor_i2c.deinit()

# KeyA.deinit()

print("Exit gas measurement.")

執行結果