Documentation
Modbus RTU/TCP
ModBus is a protocol based on RTU (serial binary) and TCP/IP packets. A connection with IP-Symcon is possible via LAN or serial gateway.
The following devices are supported by IP-Symcon:
Integration in IP-Symcon
First a "ModBus" instance has to be added within IP-Symcon. There are several variants that can be created:
| Instance | Description |
|---|---|
| ModBus Device | Instance, which can map multiple addresses (coils/registers) and supports templates (7.0 and higher) |
| ModBus Coil. | Instance which represents a single address (coil) |
| ModBus Address | Instance which represents a single address (register) |
Many templates can be found in our community: Show templates
The configuration of the parent gateway and I/O instance must then be adapted to the connected device. It must be selected via which protocol and device ID the device is addressed. The device ID is particularly important for RTU connected devices. For devices connected to TCP, this is often device ID 1.
In order to be able to establish a connection to the device, IP address and port (default:502) must be entered in the gateway's parent I/O instance.
Further configuration (screenshot below) is as follows.
| Option | Description |
|---|---|
| Unit | Data type of the variable of the device |
| Function (Read) | Function according to which the values are to be read |
| Address (Read) | Device address of the register to be read from |
| Function (Write) | Function according to which the values are to be written |
| Address (Write) | Device address of the register to be written to |
| Factor (Numeric values) | The factor multiplies or divides the received value and writes it to the device variable |
| Length (Strings) | If the length is greater than 0, it defines the precise number of characters (Bytes) queried. Note: 1 register = 2 characters (Bytes) |
| Byte order | Depending on the device, the byte order must be adapted. Often this is not documented, but must be tried out. Big Endian and Little Endian (byte swap) are the common values. |
| Emulate status | "Emulate status" means that the value of the variable is set to the new value if the write command is successful and does not depend on a read command |
| Interval | If the interval is greater than 0, the address (read) is queried cyclically on the ModBus device and the variable of the device is updated |
Due to the fact that we still support 32 bit systems Int64 values are mapped as Float64.
FunctionCodes
Depending on the FunctionCode, a suitable address must also be entered. This can be taken from the table.
The table below also provides an overview of which FunctionCode is sent with which parameterization within IP-Symcon:
| FunctionCode | Device address | Read/Write address | Surname |
|---|---|---|---|
| 0x01 (1) | 1 - 10000 | Device address - 1 | Read Coils |
| 0x05 (5) | 1 - 10000 | Device address - 1 | Write Single Coil |
| 0x02 (2) | 10001 - 20000 | Device address - 10001 | Read Discrete Inputs |
| 0x03 (3) | 40001 - 50000 | Device address - 40001 | Read Holding Registers |
| 0x10 (16) | 40001 - 50000 | Device address - 40001 | Write Multiple registers |
| 0x04 (4) | 30001 - 40000 | Device address - 30001 | Read Input Registers |
If, for example, address 40123 is to be written to (FunctionCode = 0x10), the appropriate data type (unit) must be selected and write address 122 (40123 - 40001) entered.
Some manufacturers do not adhere to this convention. It must be checked in the respective instructions or data sheets whether the device address must be subtracted depending on the function code or whether absolute addresses apply
Data types
| Data type | Sign | Bits |
|---|---|---|
| BOOL | unsigned | 1 |
| UINT8MSB | unsigned | 8 |
| UINT8LSB | unsigned | 8 |
| UINT16 | unsigned | 16 |
| UINT32 | unsigned | 32 |
| UINT64 | unsigned | 64 |
| INT8MSB | signed | 8 |
| INT8LSB | signed | 8 |
| INT16 | signed | 16 |
| INT32 | signed | 32 |
| INT64 | signed | 64 |
| FLOAT32 | signed | 32 |
| FLOAT64 | signed | 64 |
| STRING |