Chapter 14 RS485
communication
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Chapter 14 RS485 communication
The instrument use the standard Modbus-RTU protocol, all of the data are word
type(2 bytes), the range is -32767
～
32767 ,16 system.
PC command:
ID address command
Start address
Data number
CRC16
length
1 byte
1byte
2 byte
2 byte
2 byte
Ex.
0x01
0x03
0x0001
0x0001
0xD5CA
Instrument response:
ID address command
Data number
data
CRC16
length
1 byte
1 byte
1byte
N byte
2 byte
Ex.
0x01
0x03
0x02
0x02 0xBC
0xB895
If response is 01,the command is wrong.
If response is 02,the address is not correct.
If response is 03,data number is not correct.
Communication rate: 9600 (fixed)
Data: 8
Parity: None
Stop bit: 1
command 03: read the settings
command 04: read the readings 04:definition
04:definition
Address
(00)
0x00
EC/RES/SAL/TDS measuring1
reading: floating unit is uS
