Reference
This article delves into the Modbus-RTU communication protocol, detailing its parameters, data frame format, register addresses, and calibration methods for sensor networks.
Communication Protocol Description
1. Basic communication parameters
| Interface | Encoding | Data bits | Parity bits | Stop bits | Error checking | Baud rate |
|---|---|---|---|---|---|---|
| RS485 | 8-bit binary | 8 | None | 1 | CRC | 1200bit/s, 2400bit/s, 4800bit/s, 9600bit/s, 19200bit/s, 38400bit/s, 57600bit/s, 115200bit/s configurable, default 4800bit/s |
2. Data frame format definition
Using Modbus-RTU communication protocol, the format is as follows:
Initial structure ≥4 bytes of time
Address code = 1 byte
Function code = 1 byte
Data area = N bytes
Error check = 16-bit CRC code
End structure ≥4 bytes of time
Address code: The address of the sensor, which is unique in the communication network (factory default 0x01).
Function code: The function indication of the command sent by the host. This sensor reads the register function code 0x03 and writes the register function code 0x06
Data area: The data area is the specific communication data. Note that the high byte of 16-bit data is in front!
CRC code: A two-byte check code.
Host inquiry frame structure:
| Address code | Function code | Register start address | Register length | Check code low bit | Check code high bit |
|---|---|---|---|---|---|
| 1byte | 1byte | 2byte | 2byte | 1byte | 1byte |
Slave response frame structure:
| Address code | Function code | Number of valid bytes | Data area 1 | Data area 2 | Nth data area | Check code |
|---|---|---|---|---|---|---|
| 1byte | 1byte | 1byte | 2byte | 2byte | 2byte | 2byte |
General register address
| Register address | PLC or configuration address | Content | Supported function code | Definition description |
|---|---|---|---|---|
| 01F4H | 40501 | Wind speed value | 0x03 | 10 times the actual value |
| 01F6H | 40503 | Wind direction (0-7 gears) | 0x03 | Actual value (0 for due north, increasing value clockwise, 2 for due east) |
| 01F7H | 40504 | Wind direction (0-360°) | 0x03 | Actual value (0° for due north, increasing value clockwise, 90° for due east) |
| 01F8H | 40505 | Humidity value | 0x03 | 10 times the actual value |
| 01F9H | 40506 | Temperature value | 0x03 | 10 times of actual value |
| 01FAH | 40507 | Noise value | 0x03 | 10 times of actual value |
| 01FBH | 40508 | PM2.5 value | 0x03 | Actual value |
| 01FCH | 40509 | PM10 value | 0x03 | Actual value |
| 01FDH | 40510 | Atmospheric pressure value | 0x03 | Actual value |
| 01FEH | 40511 | High 16 bits of illumination value | 0x03 | Actual value |
| 01FFH | 40512 | Low 16 bits of illumination value | 0x03 | Actual value |
| 0200H | 40513 | Illumination value | 0x03 | Actual value |
| 0201H | 40514 | Rainfall value | 0x03 | 10 times the actual value |
| 07D0H | 42001 | Device address | 0x03/0x06 | 1~254 (factory default 1) |
| 07D1H | 42002 | Device baud rate | 0x03/0x06 | 0 represents 2400, 1 represents 4800, 2 represents 9600, 3 represents 19200, 4 represents 38400, 5 represents 57600, 6 represents 115200, 7 represents 1200 |
Calibration register address
| Register address | Content | Supported function code | Definition description |
|---|---|---|---|
| 6000H | Wind direction offset register | 0x06 | 0 represents the normal direction, 1 represents the direction offset by 180 degrees |
| 6001H | Wind speed zeroing register | 0x06 | Write 0xAA, wait for 10 seconds, and the device will be zeroed |
| 6002H | Rainfall zeroing register | 0x06 | Write 0x5A, and the rainfall value will be zeroed |
3. Communication protocol example and explanation
3.1. Read the wind speed value of a single register
Inquiry frame: Read value function code 0x03
| Address code | Function code | Register start address | Register length | Check code low bit | Check code high bit |
|---|---|---|---|---|---|
| 0x01 | 0x03 | 0x00 0xF4 | 0x00 0x01 | 0xC4 | 0x04 |
Response frame:
| Address code | Function code | Return valid bytes | Wind speed value | Check code low bit | Check code high bit |
|---|---|---|---|---|---|
| 0x01 | 0x03 | 0x02 | 0x00 0x7D | 0x78 | 0x65 |
Wind speed value:
007D (hexadecimal) = 125=> Wind speed value = 1.25m/s
3.2, read multiple register humidity and temperature values
Inquiry frame: read numerical function code 0x03
| Address code | Function code | Register start address | Register length | Check code low position | Check code high position |
|---|---|---|---|---|---|
| 0x01 | 0x03 | 0x01 0xF8 | 0x00 0x02 | 0x44 | 0x06 |
Response frame:
| Address code | Function code | Return valid bytes | Humidity value | Temperature value | Check code low position | Checksum high position |
|---|---|---|---|---|---|---|
| 0x01 | 0x03 | 0x04 | 0x02 0x92 | 0xFF 0x9B | 0x5A | 0x3D |
Humidity value:
0292 (hexadecimal) = 658=> Humidity value = 65.8%RH
Temperature value: When the temperature is lower than 0℃,To solve the problem, we need to restructure the given product wiki content according to the specified document structure. The key steps involve identifying sections from the original content and mapping them to the target structure while ensuring all information is preserved and formatted correctly.
Installation Instructions
When measuring wind speed and direction, the N-shaped direction on the weather station sensor should be installed facing due north to avoid errors.
The applicable range of the bottom mounting bar: 46-51mm.
The following installation methods are recommended (the bracket needs to be purchased or built by yourself)
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