User Manual

QM7590L Us er Manual http://www.qunbao.com/
Shanghai hitdo Industrial Co., Ltd TRANBALL Brand Division Page6
Communication Protocol
The product uses RS485 MODBUS-RTU standard protocol format, all operation or reply commands
are hexadecimal data. The default device address is 1 when the device is shipped, the default baud rate is
9600, 8, n, 1
1. Read Data (Function id 0x03)
Inquiry frame (hexadecimal), sending example: Query 1# device 1 data, the host computer sends the
command:01 03 00 00 00 05 85 C9 .
Device ID
Function id
Start Address
Data Length
CRC16
01
03
00 00
00 05
85 C9
For the correct query frame, the device will respond with data:01 03 0A 00 7D 00 00 00 00 00 00 00 00
19 E4 , the response format is parsed as follows:
Device
ID
Function
id
Data
Length
Data 1
Data 2
Data 3
Data 4
Data 5
Check
Code
01
03
0A
00 79
00 7A
00 7B
00 7C
00 7D
19 E4
Data Description: The data in the command is hexadecimal. Take data 1 as an example. 00 79 is
converted to a decimal value of 121. If the data magnification is 100, the actual value is 121/100=1.21.
Others and so on.
2. Data Address Table
Address
Start Address
Description
Data type
Value range
40001
00 00
carbon dioxide
Read Only
0~65535
40002
00 01
temperature
Read Only
0~65535