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modbus_rtu_client

modbus_rtu_client#

Overview#

This example demonstrates how to use Modbus RTU protocol to communication.

FreeModbus supports bellow feature:

  • Read coil(0x01)

  • Read discrete inputs(0x02)

  • Read holding registers(0x03)

  • Read input registers(0x04)

  • Write single coil(0x05)

  • Write single holding register(0x06)

  • Write board LED status(0x0d)

  • Read board LED status(0x0e)

  • Write multiple coils(0x0f)

  • Write multiple holding registers(0x10)

Running the demo#

If the test passes, serial port output:

Modbus RTU Client Example Start!

Use the MIMXRT1180-EVK board as modbus Server simulator, write board LED status(0x0d) to control LED(D6, D7) light

Supported Boards#

MIMXRT1180-EVK
Hardware requirements

  • Mini/micro USB cable

  • MIMXRT1180-EVK board

  • Personal Computer

Board settings

No special settings are required.

Prepare the Demo

  1. Connect a USB cable between the host PC and the OpenSDA USB port on the target board.

  2. Use Dupont wire to connect the pin of the two MIMXRT1180-EVK boards

    J44-18(TX)----J44-20(RX)
J44-20(RX)----J44-18(TX)
J44-17(GND)---J44-17(GND)

  3. Open a serial terminal with the following settings:

    • 115200 baud rate

    • 8 data bits

    • No parity

    • One stop bit

    • No flow control

  4. Write the program to the flash of the target board.

  5. Press the reset button on your board to start the demo. Note: The serial terminal of both boards must be opened.

IMX943-EVK
Hardware requirements

  • Mini/micro USB cable

  • IMX943-EVK board

  • MIMXRT1180-EVK board

  • Personal Computer

Board settings

No special settings are required.

Prepare the Demo

  1. Connect a USB cable between the host PC and the OpenSDA USB port on the target board.

  2. Connect IMX943-EVK board and MIMXRT1180-EVK board with Dupont wire

    IMX943-EVK      J48-2(RX)----J44-18(TX)      MIMXRT1180-EVK
IMX943-EVK      J48-4(TX)----J44-20(RX)      MIMXRT1180-EVK
IMX943-EVK      J47-14(GND)---J44-17(GND)    MIMXRT1180-EVK

  3. Open a serial terminal with the following settings:

    • 115200 baud rate

    • 8 data bits

    • No parity

    • One stop bit

    • No flow control

  4. Download the modbus_rtu_client program to IMX943-EVK board.

  5. Download the modbus_rtu_server program to MIMXRT1180-EVK board.

  6. Either re-power up your board or launch the debugger in your IDE to begin running the example.

  7. Note: MODBUS_RTU uses LPUART11, which is cm7_core0 core default serial port, please make sure that there is no output on the serial port of cm7_0 image to avoid affecting the modbus function.

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