Add CJMCU-8128 support

[riochicken]

Hi,

It would be excellent to get CJMCU-8128 support to ESPhome, my new home will have a CO2 system installed and I would like to keep monitoring this constantly since new houses don't seem to have any natural ventilation systems anymore.

Thank you in advance!

Kind regards Richard

[idavydov]

CJMCU-8128 is three different sensors on the same board:

• CCS881 (eCO2 & TVOc)
• BMP280 (temperature & pressure)
• Si7021 (temperature & humidity)

All of them are already supported by ESPHOME (amazing, I'm really impressed).

Here is the config which works for me:

sensor:
  - platform: bmp280
    temperature:
      name: "Temperature (BMP280)"
      id: bmp280_temperature
      oversampling: 16x
    pressure:
      name: "Pressure"
    address: 0x76
    update_interval: 60s
  - platform: htu21d
    temperature:
      name: "Temperature (Si7021)"
    humidity:
      name: "Humidity"
      id: si7021_humidity
    address: 0x40
    update_interval: 60s
  - platform: ccs811
    eco2:
      name: "CCS811 eCO2 Value"
    tvoc:
      name: "CCS811 Total Volatile Organic Compound"
    temperature: bmp280_temperature
    humidity: si7021_humidity
    address: 0x5A
    update_interval: 60s

Please note that:

• Temperature and humidity parameters for CCS811 are not required. But when used they are supposed to improve the precision by correcting for changes in humidity and temperature. So it's quite handy that this board have sensors for humidity and temperature.
• It seems that some versions of CJMCU-8128 have HDC1080, not Si7021. You need to change your settings accordingly. There might be also other differences, e.g., different addresses.
• You need to take special care calibrating the sensor. First, run it for 48 hours. Then you need to set the baseline (see here, ideally somewhere in the fresh air). Finally, they recommend a periodic baseline correction, which I am not sure is implemented in the esphome module for CCS881.
• I have an impression that CCS881 is not a very precise sensor; good CO2 sensors are expensive.

[christiaangombert]

To build up on the work of @idavydov as posted above, I made some minor adjustments to the configuration:

i2c:
  sda: 21
  scl: 22

sensor:
  - platform: bmp280
    temperature:
      name: "Temperature (BMP280)"
      id: bmp280_temperature
      oversampling: 16x
    pressure:
      name: "Pressure (BMP280)"
      id: bmp280_pressure
    address: 0x76
    update_interval: 60s
  - platform: hdc1080
    temperature:
      name: "Temperature (HDC1080)"
      id: hdc1080_temperature
    humidity:
      name: "Humidity (HDC1080)"
      id: hdc1080_humidity
    address: 0x40
    update_interval: 60s
  - platform: ccs811
    eco2:
      name: "eCO2 (CCS811)"
      id: ccs811_eco2
    tvoc:
      name: "Total Volatile Organic Compound (CCS811)"
      id: ccs811_tvoc
    temperature: bmp280_temperature
    humidity: hdc1080_humidity
    address: 0x5A
    update_interval: 60s

This code was tested om a Wemos D1 R32 board (device type: Generic ESP32 WROVER module) with ESPhome version 1.16.2.

WIRING DIAGRAM:

CJMCU-8128 == Wemos D1 R32 VCC == 3v3 GND == GND SDA == SDA (IO21) SCL == SCL (IO22) WAKE == GND