Among them, add represents the communication address of the receiver; cha means a
communication channel; adds means the mailing address of the sending side; cmd is
the check bit, which is used to tell the receiver the purpose of sending data; DATA is a
sequence of messages that hold the messages to be transmitted during the transmission;
end is the end bit, indicating the end of the transmission of the system.
(1) The purpose of including the sender address in the protocol is to facilitate the
receiver to determine the source of the message;
(2) All instructions are sent in hexadecimal format;
(3) CMD is 0x01 when obtaining the data instruction of single-chip microcomputer.
CMD is 0x02 when single-chip microcomputer responds;
(4) When CMD is 0x01, the DATA store the query instruction, and when CMD is
0x02, the DATA store the data of temperature and humidity;
(5) When the wireless module fails to receive the single-chip microcomputer data
packet in 5 s, it sends the data again. If the above actions are repeated for three
times and no response is received, the address of this receiver will be reported and
the request data will not be sent to this address in the next cycle.
Fig. 4. Transmission module circuit
Table 1. Transmission protocol of obtaining the data of the single-chip microcomputer
add (2B)
cha (1B) adds (2B)
cmd (1B) DATA (nB)
end (1B)
Receiver address Channel Sender address Check bit Query command End bit
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Y. Xu and Y. Yang