SM1882B Us er Ma nual
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needs to change the query command of the software at the same time.
4 Read and Modify Baud Rate
(1) Read baud rate
The device default factory baud rate is 9600. If you need to change it, you can change it according to
the following table and the corresponding communication protocol. For example, read the current device's
baud rate ID, the command is:01 03 00 67 00 01 35 D5 , its format is parsed as follows.
Device ID
Function id
Start Address
Data Length
CRC16
01
03
00 67
00 01
35 D5
Read the baud rate encoding of the current device. Baud rate encoding: 1 is 2400; 2 is 4800; 3 is 9600;
4 is 19200; 5 is 38400; 6 is 115200.
For the correct query command, the device will respond, for example the response data is: 01 03 02
00 03 F8 45, the format of which is as shown in the following table:
Device ID
Function id
Data Length
Rate ID
CRC16
01
03
02
00 03
F8 45
coded according to baud rate, 03 is 9600, ie the current device has a baud rate of 9600.
(2)Change the baud rate
For example, changing the baud rate from 9600 to 38 400, ie changing the code from 3 to 5, the
command is: 01 06 00 67 00 05 F8 1601 03 00 66 00 01 64 15 .
Device ID
Function id
Start Address
Target Baud Rate
CRC16
01
03
00 66
00 01
64 15
Change the baud rate from 9600 to 38400, changing the code from 3 to 5. The new baud rate will take
effect immediately, at which point the device will lose its response and the baud rate of the device should
be queried accordingly. Modified.
5 Read Correction Value
(1) Read Correction Value
When there is an error between the data and the reference standard, we can reduce the display error
by adjusting the correction value. The correction difference can be modified to be plus or minus 1000, t hat
is, the value range is 0-1000 or 64535 -65535. For example, when the display value is too small, we can
correct it by adding 100. The command is: 01 03 00 6B 00 01 F5 D6 . In the command 100 is hex 0x64 If
you need to reduce, you can set a negative value, such as -100, corresponding to the hexadecimal value of
FF 9C, which is calculated as 100-65535=65435, and then converted to hexadecimal to 0x FF 9C. The
correction value starts from 00 6B. We take the first parameter as an example. The correction valu e is read
and modified in the same way for multiple parameters.
Device ID
Function id
Start Address
Data Length
CRC16
01
03
00 6B
00 01
F5 D6
For the correct query command, the device will respond, for example the response data is: 01 03 02
00 64 B9 AF, the format of which is as shown in the following table:
Device ID
Function id
Data Length
Data value
CRC16
01
03
02
00 64
B9 AF
In the response data, the first byte 01 indicates the real address of the current device, and 00 6B is the
first state quantity correction value register. If the device has multiple parameters, other parameters
operate in this way. The same, the general temperature, humidity have this parameter, the light generally
does not have this item.
(2)Change correction value
