Enter a register address from the manual

The portal works with the protocol address, the address that the gateway puts in its request to the Modbus device. The first register has address 0. The Adres (address) field converts nothing. If you enter 40001 from the manual, the gateway also requests address 40001.

What you need

• The register table from the manual of the Modbus device.
• A Modbus device on the gateway, added as described in Add Modbus devices.
• The role Owner, Admin or Technician in your organisation.

Determine the address and function

The table shows what to enter for the common notations.

In a classic number, the first digit gives the register type. A 4 is a holding register and a 3 is an input register. You choose that type in Functie (function). Then subtract 40001 or 30001 from the number. For 6 digits, subtract 400001 or 300001. The result is the address.

A hexadecimal address in the manual is usually already the protocol address. Only convert it to a decimal number, because the Adres field does not accept hex. So 0x0046 becomes address 70 (4 × 16 + 6).

If the manual names the function code itself, such as 03 or 04, choose that one. If a register number has no leading 3 or 4, check whether the manual counts from 0 or from 1. If it counts from 1, subtract 1.

A 5-digit number is not always classic. Some Modbus devices use protocol addresses above 10000, such as 40000 (0x9C40) or 45056 (0xB000). If the manual says "base 0" or gives a hex address, enter that address without subtracting anything. The course explains how to calculate the address from 40001.

Enter the address and function

After these steps, the gateway reads the register at the converted address.

1. Open the gateway list

   Open Gateways in the menu.

2. Open the gateway

   Click the gateway of the Modbus device.

3. Open the Modbus device

   Under Modbus devices, click the Modbus device. The Modbus apparaat (Modbus device) page opens with the registers.

4. Open the window

   Click Register toevoegen (Add register). To change an existing register, click the pencil in its row (Register bewerken, Edit register).

5. Enter the name

   In Naam (name), enter a name, such as Voltage L1.

6. Choose the function

   In Functie, choose the function from the table above. A new register is set to Read input registers (4) by default.

7. Enter the address

   In Adres, enter the converted address, such as 0 for 30001.

8. Fill in the other fields

   Set Datatype (data type) and the other fields as described in Set up registers.

9. Save the register

   Click Toevoegen (Add), or Opslaan (Save) if you are editing a register. The portal sends the new setting to the gateway.

Each address occurs once per Modbus device, even with a different function. A register at 30001 and one at 40001 both fall on address 0, so only one of the two can exist on the Modbus device. For the second one, the portal reports Dit adres bestaat al op dit apparaat (this address already exists on this device).

In the template editor, you enter the address in the same way, as in Create a custom template. The function list is called Function code there. If a template has two registers at the same address, a Modbus device with that template gets only one of them.

Check the address with a known value

A shifted address usually gives no error message, because the Modbus device answers with the content of another register. So compare a value that you can also read on the display of the Modbus device, such as a voltage. Once the gateway has read the register, the value appears in the Laatste waarde (last value) column.

The table shows what a wrong address or a wrong function produces.

A 32-bit value spans two registers, so an address one off reads half of two values. If the manual lists the 32-bit values at 30001, 30003 and 30005, the addresses should be 0, 2 and 4.

If the address is correct and a 32-bit value stays impossible, check the byte order. If no value arrives from the whole Modbus device, follow Modbus device shows no values. Other deviations are covered in Values are wrong.