Arduino Modbus Slave

Projects Networking, Protocols, and Devices
1

Hi Friends, I want to communicate with arduino slave from Weintek HMI using modbus rtu protocol over rs485, I am Using Modbus_Master_Slave Libraries basic example.
Max485 ic is used for interfaceing arduino slave to hmi.
but i am unable to communicate with Hmi.
Really not know where the problem is.

arduino(nano)TX >> MAX485(DI)
arduino(nano)RX >> MAX485(DO)
arduino(nano)D13 >> MAX485 (RE,DE)

MAX485(A) >> HMI (DATA+)
MAX485(B) >> HMI (DATA-)

CODE and HMI setting are attached below

ARDUINO_MODBUS_SLAVE_HMI.png
ARDUINO_MODBUS_SLAVE_HMI.png983×727 60.7 KB

MODBUS_ARDUINO_SLAVE_TEST.ino (819 Bytes)

2

19200, E, 8, 1

Why are you using even parity? Is the Arduino setup for even parity? Does the library handle even parity?

3

Does the library handle even parity?

Yes, it does or better the provided configuration byte does it. But parity is only possible on the hardware serial interface(s).

arduino(nano)TX >> MAX485(DI)
arduino(nano)RX >> MAX485(DO)
arduino(nano)D13 >> MAX485 (RE,DE)

MAX485(A) >> HMI (DATA+)
MAX485(B) >> HMI (DATA-)

Please provide schematics of the connection between the MAX485 chip and the Nano. The chip needs some additional components to work correctly with the Arduino.

Is your HMI really acting as a ModBus master (your Arduino is configured as slave)? What register addresses does it expect? Post a link to the manual of that device!

4

adwsystems:
19200, E, 8, 1

Why are you using even parity? Is the Arduino setup for even parity? Does the library handle even parity?

Yes Library handle Even Parity.
or if i use no parity bit same thing happen no communicatio.

5

pylon:
Yes, it does or better the provided configuration byte does it. But parity is only possible on the hardware serial interface(s).

Please provide schematics of the connection between the MAX485 chip and the Nano. The chip needs some additional components to work correctly with the Arduino.

Is your HMI really acting as a ModBus master (your Arduino is configured as slave)? What register addresses does it expect? Post a link to the manual of that device!

User manual for Weintek HMI

or connection are i mention earlier . i use arduino MAX485 Board

arduino(nano)TX >> MAX485(DI)
arduino(nano)RX >> MAX485(DO)
arduino(nano)D13 >> MAX485 (RE,DE)

MAX485(A) >> HMI (DATA+)
MAX485(B) >> HMI (DATA-)

with no extra components

6

or connection are i mention earlier . i use arduino MAX485 Board

Post schematics of that board!

And post the MACRO code (or however you would call that "language") you run on the HMI.