Modbus¶
The probe can be addressed directly using the MODBUS protocol, to request the measured CO2 values. The parameters highlighted in yellow should be selected according to the table below.
| Important: In order to communicate directly with the digital probe via MODBUS, please use the E2-05XX-MOD cable. The digital MODBUS protocol is delivered over RS485. |
|---|
Command: (MSB first)¶
| Probe address | Command ID | Start address | Number of records | MODBUS CRC1 | ||
|---|---|---|---|---|---|---|
| 0x00 | 0x04 | 0x00 | 0x00 | 0x00 | 0x00 | 0x0000 |
1 CRC calculation according to MODBUS standard
Probe address: 0…255, if '0' then all probes respond regardless of the address.
| 0x00 | 0x04 | Serial number | CO2 | ||
|---|---|---|---|---|---|
| 0x00000000 | 0x0000 | ||||
| 0x00 | 0x02 | Serial number | |||
| 0x00000000 |
Response¶
| 0x00 | 0x04 | 0x00 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 | 0x0000 |
|---|---|---|---|---|
Data format¶
Serial number (unsigned int): 0…232-1¶
Response in the event of an error¶
| 0x00 | 0x84 | 0x00 | 0x0000 |
|---|---|---|---|
| 0x02 | Start address and number of records invalid |
|---|---|
| 0x03 | Number of records invalid |
Sensor faults¶
In the event of a short circuit or open circuit at the probe, a value of 19999 is output for the measured value concerned.
| Coils | Bit | Read/Write | 1 … 9’999 | 0x01 | Read Coils |
|---|---|---|---|---|---|
| 0x05 | Write Single Coil | ||||
| 0x0F | Write Multiple Coils | ||||
| Discrete inputs | Bit | Read Only | 10’001 … 29’999 | 0x02 | Read Discrete Inputs |
| Input registers | 16-bit | Read Only | 30’001 … 39’999 | 0x04 | Read Input Register |
| Holding registers | 16-bit | Read/Write | 40’001 … 49’999 | 0x03 | Read Holding Registers |
| 0x06 | Write Single Register | ||||
| 0x10 | Write Multiple Registers |
| Note: Coils and registers in Modbus are addressed starting at zero. Therefore coils numbered 1…16 are addressed as 0…15 or registers numbered (e.g. 10'001…10'016 are addressed as 10'000…10'015) |
|---|
Connection timeout: When TCP connection is open and for more than 30 seconds no communication is performed, the device automatically closes the TCP connection. In case of a communication interruption, this prevents the socket being blocked.
Additional MODBUS details can be found here: MODBUS in RMS.