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图 14
I
2
C Reading sequence
diagrams
Reference sequence:
图 15 Reference sequence diagram
Note: the actual test data
refer to the single bus-processing example.
8.3Single bus communication (
ONE-WIRE
）
◎Single bus description
DHT12 A simplified single-bus communication. That only a single bus cable, system of data
exchange,Control is done by a single bus communication. Devices (hosts) through a drain or a
three-State port is connected to the data cable to allow device does not send data will be released
when the bus, while letting the other device uses the bus; usually require add-ins a single bus
around 4.7KΩPull-up resistor, so that when the bus is idle by default high State. Because they are
the master-slave relationship, only when the host calls the sensor, the sensor responds, so host
access must be strictly followed during single bus timing, timing disorder if will not be able to
correctly read data of temperature and humidity.
◎Single bus transfer data definitions
SDA PIN for client hosts DHT12 Communication and synchronization between, by-wire data
format, a transfer 40 Data high first. Specific communicationSequential as shown in the following
figure, communication formats described in the following table.
图 16 Single bus communication timing description
◎Single bus data example:
The name
Single bus format definition
The
starting
signal
Host data bus (SDA) Down over time (18ms), Tells sensors to prepare data