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1) Step 1: MCU send out start signal to RHT02 and RHT02 send response signal to MCU

Data-bus's free status is high voltage level. When communication between MCU and RHT02 begins, MCU

will pull low data-bus and this process must beyond at least 1~10ms to ensure RHT02 could detect MCU's signal,

then MCU will pulls up and wait 20-40us for RHT02's response.

When RHT02 detect the start signal, RHT02 will pull low the bus 80us as response signal, then RHT02 pulls

up 80us for preparation to send data. See below figure:

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2). Step 2: RHT02 send data to MCU

When RHT02 is sending data to MCU, every bit's transmission begin with low-voltage-level that last 50us, the

following high-voltage-level signal's length decide the bit is "1" or "0". See below figures: