User Manual
HC‐12WIRELESSRFUARTCOMMUNICATIONMODULEV2.4USERMANUAL
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PAGE 4
⑶ The four kinds of UART transmission mode
HC-12 module UART transmission mode default is FU3. At this point, the module works at
full speed, the idle current is about 16mA. In this mode, the wireless transmission module will
automatically adjust the air baud rate according to the baud rate of UART baud rate, the
corresponding relations are shown in the following table:
UART baud rate
1200
bps
2400
bps
4800
bps
9600
bps
19200
bps
38400
bps
57600
bps
115200
bps
air baud rate 5000bps 15000bps 58000bps 236000bps
In order to make the communication distance as far as possible, can be set to low UART
baud rate. If it is short time to transfer large amounts of data, the UART baud rate for high baud
rate, at the expense of communication distance.
The receiving sensitivity of different air conditions the baud rate module as shown in the
following table:
air baud rate 500bps 5000bps 15000bps 58000bps 236000bps/250000bps
receiving sensitivity -124dBm -116dBm -111dBm -106dBm -100dBm
Generally, the reception sensitivity decreases by 6~10 dB, and the communication distance
is reduced by half.
In the module "SET" pin is low level, you can set the UART transmission mode through the
AT command (see the introduction of the following chapters).
FU1 mode is more power saving mode, at this time, the idle work current of the module is
about 3.6mA. This mode can also set up 8 kinds UART baud rate is shown in the table above, but
the air uniform 250000bps baud rate, short communication distance.
FU2 mode is power saving mode, at this time the module idle work current is about 80μA.
This mode module supports only 1200 bps, 2400 bps and 4800 bps UART baud rate, air baud
rate is uniform 250000bps, short communication distance. At the same time, in the FU1 and FU3
mode set to FU2 mode, more than 4800 UART baud rate will be automatically reduced to 4800
bps. FU2 mode, only the transfer of a small amount of data (each packet within 20 bytes), packet
transmission time interval can not be too short (preferably in more than 2 seconds), otherwise it
will result in data loss.
FU4 mode for ultra long distance communication mode, the UART baud rate is fixed at
1200 bps, the air baud rate is 500bps. From the other mode to FU4, the serial baud rate will be
automatically converted to 1200bps. In this mode, only a small amount of data is transferred
(each packet is within 60 bytes), the packet transmission time interval can not be too short
(preferably in more than 2 seconds), otherwise it will result in data loss.