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ABClogic is an algorithm for long term tracking of CO2 concentration and adjusting the
sensor characteristics in the low concentration range. The sensor stores low values of CO2
concentration from many last days, which enables taking intelligent account of periodical
CO2 concentration level increases (e.g. when rooms were used 24 hours per day over a few
days). As a result of the ABClogic algorithm, the “automatic zero calibration” of the sensor
is carried out.
The automatic calibration ABClogic, is designed for applications where rooms remain
unoccupied for several hours per day, as a result, CO2 concentration values periodically
drop to low values, similar to those outside the building. In contrast, in an environment
where the level of CO2 concentration reaches high values and doesn't drop to low values,
the ABClogic system should be switched off, because it would adjust automatic calibration
to the lowest levels, distorting the values indicated by the sensor.
In the sensor described in this document, the ABClogic function is off by default (factory
setting). The status of ABClogic function (switching on or off) can be changed by writing the
respective command (see section 4.1.1).
4. MODBUS protocol
4.1. Register map
Register
no.
R/W
Name
Values
Notes
0x0000
R
VALUE_REG
0 - 2000
CO2 concentration in [ppm]
0x0001
R
STATUS_REG
0 / 1 / 2 / 3
0-Sensor missing, 1 – correct operation, 2 –
sensor error, 3 – warm up (first 3 minutes
after start)
0x0002
R
TEST_VAL_REG
1000 (0x3E8)
Test value – to verify the correctness of
register readings
0x0003
RW
PASS_REG
1234 (0x04D2)
password register
0x0004
RW
COMMAND_REG
1 / 2 / 3 / 4 / 5 / 6
command register
0x0005
RW
PARAM_REG
Refer to command
table
parameter register
0x0006
R
--
0
reserved
0x0007
R
--
0
reserved
0x0008
R
--
0
reserved
0x0009
R
--
0
reserved
0x000A
R
--
0
reserved
0x000B
R
DEV_ID_REG
0xC100
Device identification
0x000C
R
SOFT_VER_REG
0 – 0x9999
Software version
(e.g. 0x3210 means software 3.21a)