Adding a CO2 sensor to the NFC Jukebox

I’ve previously put together a CO2 sensor and a NFC jukebox, as separate small projects using ESPHome and integrating with my Home Assistant.

Initially, I had separate USB cables running to each device. While this worked, I wanted a cleaner setup, especially since both devices were in the same room. I looked for a Y-type cable, so I could have one less cable dangling, but managed to find a neater and more efficient solution.

I ordered a M5stack Grove Hub (for about 4 EUR), plugged it into the ESP32, and plugged both sensors into the HUB. After this, all I had to do was edit my code so has to have both sensors handled by the same ESP32.

As far as I understand it, the reason this works is that both sensors use different I2C addresses, as can be seen in the ESPHome .yaml. The NFC reader uses address: 0x28, whereas the CO2 sensor uses address: 0x62.

A M5Stack SD40 CO2 sensor and the RFID2 NFC reader connected to a M5Stack Grove HUB, all connected to the M5Stack Atom Lite ESP32

Updating the .yaml code

All it took was modifying the original .yaml from the NFC Jukebox, adding in the block for the CO2 Sensor, and then flash it OTA (wirelessly):

# CO2 Sensor
sensor:
  - platform: scd4x
    id: scd40
    automatic_self_calibration: False
    co2:
      name: "CO2"
      id: co2
      accuracy_decimals: 1
    temperature:
      name: "Temperature"
      id: temperature
      accuracy_decimals: 2
    humidity:
      name: "Humidity"
      id: humidity
      accuracy_decimals: 1
    address: 0x62
    update_interval: 10s
  - platform: template
    name: "VPD"
    icon: "mdi:gauge"
    id: gr2_ace_vpd
    lambda: |-
          return (((100 - id(humidity).state) / 100) * (0.6108 * 2.718281828459045 * (17.27 * ((id(temperature).state)) / (((id(temperature).state)) + 237.3))));
    update_interval: 10s
    unit_of_measurement: kPa
    accuracy_decimals: 2
    filters:
      - filter_out: nan
  - platform: uptime
    name: Uptime

Full .yaml for Atom Lite ESP32 with RFID2 + SD40 CO2 sensor

substitutions:
  name: m5stack-rfid-co2
  friendly_name: M5Stack RFID Tag Reader with CO2
  
esphome:
  name: ${name}
  friendly_name: ${friendly_name}
 
esp32:
  board: m5stack-atom
  framework:
    type: esp-idf
 
# Enable logging
logger:
 
# Enable Home Assistant API
api:
  encryption:
    key: <randomlygeneratedkey>
 
ota:
  - platform: esphome
    password: !secret ota_password
 
wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password
 
  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "m5stack-rfid-co2 Fallback Hotspot"
    password: <randompassword>
 
# RFID Reader Sensor
external_components:
  - source:
      type: git
      url: https://github.com/chill-Division/M5Stack-ESPHome/
      ref: main
    components: mfrc522_i2c
 
# The I2C mapping for the Atom Lite
i2c:
  sda: 26
  scl: 32
  scan: true
  id: bus_1
  
# RFID Reader Sensor
rc522_i2c:
  address: 0x28
  on_tag:
    then:
      - homeassistant.tag_scanned: !lambda 'return x;'
 
# CO2 Sensor
sensor:
  - platform: scd4x
    id: scd40
    automatic_self_calibration: False
    co2:
      name: "CO2"
      id: co2
      accuracy_decimals: 1
    temperature:
      name: "Temperature"
      id: temperature
      accuracy_decimals: 2
    humidity:
      name: "Humidity"
      id: humidity
      accuracy_decimals: 1
    address: 0x62
    update_interval: 10s
  - platform: template
    name: "VPD"
    icon: "mdi:gauge"
    id: gr2_ace_vpd
    lambda: |-
          return (((100 - id(humidity).state) / 100) * (0.6108 * 2.718281828459045 * (17.27 * ((id(temperature).state)) / (((id(temperature).state)) + 237.3))));
    update_interval: 10s
    unit_of_measurement: kPa
    accuracy_decimals: 2
    filters:
      - filter_out: nan
  - platform: uptime
    name: Uptime
 
text_sensor:
  - platform: version
    hide_timestamp: true
    name: "${friendly_name} ESPHome Version"
    entity_category: diagnostic
  - platform: wifi_info
    ip_address:
      name: "${friendly_name} IP Address"
      icon: mdi:wifi
      entity_category: diagnostic
    ssid:
      name: "${friendly_name} Connected SSID"
      icon: mdi:wifi-strength-2
      entity_category: diagnostic      

This is literally all it takes. The same ESP32 can now take the information from both sensors simultaneously.
If I ever want to expand on this project, I could easily integrate additional sensors by using the remaining slot in the Hub.