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5.1 Overall Communication Process (Figure 2, below)

When MCU sends a start signal, DHT11 changes from the low-power-consumption mode to the

running-mode, waiting for MCU completing the start signal. Once it is completed, DHT11 sends a

response signal of 40-bit data that include the relative humidity and temperature information to

MCU. Users can choose to collect (read) some data. Without the start signal from MCU, DHT11

will not give the response signal to MCU. Once data is collected, DHT11 will change to the low-

power-consumption mode until it receives a start signal from MCU again.

Figure 2 Overall Communication Process

5.2 MCU Sends out Start Signal to DHT (Figure 3, below)

Data Single-bus free status is at high voltage level. When the communication between MCU and

DHT11 begins, the programme of MCU will set Data Single-bus voltage level from high to low

and this process must take at least 18ms to ensure DHT’s detection of MCU's signal, then MCU

will pull up voltage and wait 20-40us for DHT’s response.

Figure 3 MCU Sends out Start Signal & DHT Responses