MultiMultiGas

DFRobot sells a series of I2C/UART-based gas sensors that come calibrated and are much more accurate than cheaper sensors like the analog MQ-series. These sensors can have the lower 2 bits of their I2C addresses set using switches and the middle bits set via software, so it's possible to use all of them on one I2C bus. You can query the sensor at a given address to find out what kind of gas it reports on.

This library encapsulates the DFRobot MultiGasSensor library to provide a simple interface for querying a specific gas sensor (if available) without having to worry about gas type to I2C address mapping.

Supported gases: CL2, CO, H2, H2S, HF, HCL, O2, O3, NH3, NO2, PH3, SO2.

Arduino / PlatformIO

Add the library and its DFRobot dependency:

lib_deps =
    https://github.com/romkey/multi-multigas
    https://github.com/DFRobot/DFRobot_MultiGasSensor

Basic usage:

#include <multi-multigas.h>

MultiMultiGas sensors;

void setup() {
  Wire.begin();
  if (!sensors.begin()) {
    Serial.println("No sensors found");
    return;
  }
}

void loop() {
  if (sensors.has_co()) {
    Serial.println(sensors.get_co());
  }
}

Build the included example:

pio run -e example

Enable debug logging by defining MULTI_MULTIGAS_DEBUG.

I2C address range

begin() scans I2C addresses 0x60–0x7F, which is the range used by DFRobot gas sensors. Use change_addrs() to reassign the address group when configuring multiple sensors on one bus.

Address planning

Each sensor type has a default address range. The lower 2 bits are set with hardware switches; the middle bits can be changed in software with MultiMultiGas::change_addrs(). DFRobot divides the range into 8 groups of 4:

Group	Addresses
1	0x60–0x63
2	0x64–0x67
3	0x68–0x6B
4	0x6C–0x6F
5	0x70–0x73
6 (default)	0x74–0x77
7	0x78–0x7B
8	0x7C–0x7F

Groups 7 and 8 are outside the 7-bit addresses an I2C master can reach, so avoid them.

ESPHome

The external component lives at components/multi_gas/.

esphome:
  name: my-sensor
  libraries:
    - Wire
    - multi-multigas=https://github.com/romkey/multi-multigas#2.0.0

external_components:
  - source: github://romkey/multi-multigas
    components: [multi_gas]

esp32:
  board: esp32-s3-devkitc-1
  framework:
    type: arduino

i2c:
  - id: gas_bus
    sda: GPIO21
    scl: GPIO22
  - id: other_bus
    sda: GPIO18
    scl: GPIO19

multi_gas:
  id: gases
  i2c_id: gas_bus
  update_interval: 60s
  debug: true
  detected_gas_sensors:
    name: "Detected Gas Sensors"
  duplicate_gas_sensors:
    name: "Duplicate Gas Sensors"
  co:
    name: "Carbon Monoxide"
  h2s:
    name: "Hydrogen Sulfide"
  o2:
    name: "Oxygen"

Notes:

• multi_gas: is correct — it is a top-level component, not under sensor:.
• external_components is required — use github://romkey/multi-multigas (ESPHome finds components in components/ automatically).
• Use i2c_id: to select which I2C bus when you have more than one. With a single i2c: block, i2c_id is optional.
• Use framework: type: arduino. The DFRobot dependency needs Arduino.h and Wire.h, so keep Wire in libraries: — but note the component itself performs all I2C through the ESPHome bus selected by i2c_id, not through Wire.
• Set logger: level: DEBUG to see the per-address scan, detected gas types, warmup, and skipped publishes. Adding debug: true additionally probes the whole 0x08–0x77 range at startup so its output can be compared directly against the i2c: component's own scan: true results.
• An address that acknowledges on the bus but does not report a supported gas type is logged as a warning (regardless of debug:) and retried on every update. Sensors that are still booting behave this way, so they get picked up a minute or two later and the text sensors are republished.
• Only one sensor per gas type can be read, since each gas has a single slot. If two sensors report the same type the lower address wins and the other is logged as a warning rather than silently ignored.
• Configure only the gas sensors you want exposed; each is optional.
• detected_gas_sensors is an optional text sensor whose state is the comma-separated list of gas types found on the bus, for example CO, H2S, O2. It is published as soon as the scan finishes rather than after the warmup, and lists everything detected even if you did not configure a sensor for it.
• duplicate_gas_sensors is an optional text sensor listing every gas type that was found more than once, with the I2C address of each instance, for example CO (0x60), CO (0x64). The first address in each run is the one being read. It is empty when there are no duplicates.
• O2 is reported in percent; other gases use ppm.
• Sensors need about 3 minutes to warm up before readings are published.
• If nothing at all answers in 0x60–0x7F at startup, the component marks itself as failed. If something answers but cannot be identified, the component stays up and keeps retrying.
• If you see multi_gas cannot be loaded via YAML (no CONFIG_SCHEMA), ESPHome is importing a leftover component directory that no longer has an __init__.py. Delete .esphome/external_components/ (a "Clean Build Files" does not remove it) and restart the ESPHome dashboard or add-on, which also clears its in-memory module cache.

API

Method	Description
begin(wire)	Scan 0x60–0x7F and initialize found sensors. Returns true if at least one sensor was found.
has_co() etc.	Returns whether that gas type was detected.
get_co() etc.	Read concentration in ppm (or % for O2 via DFRobot library). Returns NaN if not available.
get_co_raw() etc.	Read raw sensor voltage.
get_co_i2c_addr() etc.	I2C address of the detected sensor.
unidentified_count() / unidentified_addr(i)	Addresses that acknowledged but reported no supported gas type.
retry_unidentified()	Re-run identification on those addresses. Returns how many sensors were newly registered.
duplicate_count() / duplicate_addr(i) / duplicate_gas(i)	Sensors whose gas type is already provided by a lower address.
change_addrs(start, end, group, wire)	Change the address group for sensors in a range.

License

MIT