MODBUS TD-500: Difference between revisions
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= '''Example of TD-500 sensor polling in Terminal program''' = | = '''Example of TD-500 sensor polling in Terminal program''' = | ||
1 | 1 response - response to a request via LLS protocol | ||
2 | 2 response - response to a request via ModBUS RTU protocol | ||
TD-500 polling in the Terminal program | |||
$01$03$00$00$00$04$44$09 Command to poll a sensor via Modbus RTU protocol | |||
* 01 | * 01 Sensor network address | ||
* 03 | * 03 Requested command to read registers | ||
* 00 00 | * 00 00 Register starting from which data is requested | ||
* 00 04 | * 00 04 Number of requested registers | ||
* 44 09 | * 44 09 CRC-16 MODBUS checksum | ||
If you specify a different network address, you need to recalculate the checksum. But there is no point in changing the network address, since the sensor will respond to any network address. | |||
== '''Checksum calculation''' == | == '''Checksum calculation''' == | ||
Revision as of 10:05, 9 December 2024
Description of MODBUS registers for TD-500
Port settings
Baud rate: 19200 kbps
Data size: 8
Stop-bits: 1
Parity: None
Request and response structure
REQUEST :
- (u8) Network address
- (u8) 0х03 --> Read command
- (u8) Low byte of read reg. (value is ignored)
- (u8) High byte of read reg. (value is ignored)
- (u8) Low byte of the quantity -|-|-|-|
- (u8) High byte of quantity -|-|-|-|
- (u8) CRC16 - low byte
- (u8) CRC16 - high byte
RESPONSE:
- (u8) Network address
- (u8) Confirmation of the command (always 0х03)
- (u8) Количество выгружаемых байт (always 0x08)
- (s8) Temperature
- (u8) High byte of Level
- (u8) Low byte of Level
- (u8) Always 0
- (u8) Always 0
- (u8) Always 0
- (u8) Always 0
- (u8) Always 0
- (u8) CRC16 - low byte
- (u8) CRC16 - high byte
s8 means the value is a signed integer, u8 means an unsigned integer.
Numbered addresses of the response bytes:
| Byte ordinal number | Byte ordinal number starting from 0 | Meaning |
| 1 | 0 | Temperature |
| 2 | 1 | High byte of Level |
| 3 | 2 | Low byte of Level |
| 4 | 3 | Always 0 |
| 5 | 4 | Always 0 |
| 6 | 5 | Always 0 |
| 7 | 6 | Always 0 |
| 8 | 7 | Always 0 |
Baudrate does not change.
19200, 8, n, 1
The number of bits in the package is 12x8, i.e. about 96 pcs
The network number specified in the request is not important, and the number of requested registers is also not important. The main thing is that the checksum matches. The checksum calculation is given below.
Example of TD-500 sensor polling in Terminal program
1 response - response to a request via LLS protocol
2 response - response to a request via ModBUS RTU protocol
TD-500 polling in the Terminal program
$01$03$00$00$00$04$44$09 Command to poll a sensor via Modbus RTU protocol
- 01 Sensor network address
- 03 Requested command to read registers
- 00 00 Register starting from which data is requested
- 00 04 Number of requested registers
- 44 09 CRC-16 MODBUS checksum
If you specify a different network address, you need to recalculate the checksum. But there is no point in changing the network address, since the sensor will respond to any network address.
Checksum calculation
Для того, чтобы посчитать контрольную сумму, вы можете перейти на сайт https://crccalc.com и ввести ваш запрос без знака $, выбрать HEX, CRC-16 ModBUS и нажать Calc CRC-16
Расчет контрольной суммы на сайте crccalc
Полученной значение надо записать в отправляемую команду. При этом полученное при расчете значение 0C 44 следует записать в команду как 44 0C. Обратите внимание на раскладку вашей клавиатуры. Набирать команду следует латиницей.
Response from the sensor:
01 03 08 14 04 67 00 00 00 00 00 D8 FF
- 01 - сетевой адрес
- 03 - команда, на которую датчик отвечает
- 08 - количество байтов в ответе
- 14 - температура HEX (20°C в DEC)
- 04 67 - байты уровня Big Endian HEX (в прямом порядке) (или 1127 единиц в DEC)
- 00 00 00 00 00 - резерв 5 байтов, не используется
- D8 FF - CRC-16 ModBUS контрольная сумма Little Endian HEX (Обратный порядок, т.е. FF D8)