AQC-0-0-0-0: Difference between revisions

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The AQC-0-0-0-0 is a CO2 sensor, much like the [[MH-Z19B]]. It has the same form factor and is pin compatible. Regarding the protocol it is only compatible with the MH-Z19 for the commands 0x86 and 0x87.
The AQC-0-0-0-0 is a CO2 sensor, much like the [[MH-Z19B]]. It has the same form factor and is pin compatible. Regarding the protocol it is only compatible with the MH-Z19 for the commands 0x86 and 0x87.


The sensor communicates using TTL serial, 9600 8N1.
The sensor communicates using 5V-tolerant 3.3V TTL serial, 9600 8N1.


Through reverse-engineering a firmware-dump, we've found the following command packet format:
Through reverse-engineering a firmware-dump, we've found the following command packet format:

Revision as of 03:31, 5 January 2021

The AQC-0-0-0-0 is a CO2 sensor, much like the MH-Z19B. It has the same form factor and is pin compatible. Regarding the protocol it is only compatible with the MH-Z19 for the commands 0x86 and 0x87.

The sensor communicates using 5V-tolerant 3.3V TTL serial, 9600 8N1.

Through reverse-engineering a firmware-dump, we've found the following command packet format:

Teardown

  • Bottom of PCB, as visible without destroying the sensor

    Bottom of PCB, as visible without destroying the sensor

  • Top of PCB (inside)

    Top of PCB (inside)

  • Case removed

    Case removed

Protocol

  • Query: id 01 cc p1 p2 p3 p4 p5 cs
id Device BUS id? Is 0xFF for our device, but seems variable.
cc Command (e.g. 0x86)
px Parameters, left at 00 when there are none
cs Checksum

Commands

0x86 or 0xC5: Request CO2 level

  • Parameters: none.
  • Response: FF 86 hh ll 00 00 00 00 cs, where the CO2 level is hh * 256 + ll PPM.
    • Unlike the MH-Z19B, no other info is returned except the CO2 level in PPM.

0x87: Perform manual calibration immediately

  • Parameters: none.
  • Response: none.
  • Implemented by filling the measurement history with the current value and then letting the regular calibration do its magic.

0xC1: Configure

  • With p1 set to 0x13 - 0x22: store 16 bit value in p4/p5 in the specific register. We haven't figured any of these out yet.
  • With p1 set to 0x32: commit to flash
  • With p1 set to 0xAA and p2 set to 0x00: set operation mode to 0
  • With p1 set to 0xAA and p2 set to 0x01: set operation mode to 3

0xC2: Set operation mode to 1

  • Parameters: none.
  • Response: none.

0xC3: Set operation mode to 2

  • Parameters: none.
  • Response: none.

0xC4: Dump raw measurement

  • Parameters: none.
  • Response: 5D 00 00 00 01 v1 v1 v1 v1 v2 v2 v2 v2 v3 v3 v3 v3 cs
    • Dumps three 32 bit values, no idea what they are, but we're assuming they're raw sensor values.

0xC5: Same as 0x86

See 0x86.

Operation modes

  • 0: Seems to be the same as 3.
  • 1: Continuous PPM output on serial as if command 0x86 was given continuously.
  • 2: Continuous raw diarrhea mode, keeps sending lots of debug(?) data without checksums.
  • 3: Poll mode (default)

Checksum

Same as MH-Z19B.

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