# modbus rtu master
## Overview

- This project demonstrates the modbus rtu master function
- In this example project, one board serves as rtu master and the other board serves as rtu slave. The master sends a read holding register and waits for the slave to respond to the request data.

## Note
- When using uart for modbus communication and communicating with an rtu slave, you must reset the slave first and then the host.

## Board Setting

- Please refer to the description in the specific development board {ref}` pin description <lab_board_resource>` section.
- Connect the modbus uart pins of the two boards.
- The two boards must be connected to the GND of both sides to share the ground to ensure signal transmission.

## Running the example

- Run slave first, then master
- When the project runs correctly, the serial terminal will output the following information:

```console
modbus rtu master example
recv slave msg len:25
Hold Registers[0~9]:0x0000 0x0001 0x0002 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009

recv slave msg len:25
Hold Registers[0~9]:0x0000 0x0001 0x0002 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009

recv slave msg len:25
Hold Registers[0~9]:0x0000 0x0001 0x0002 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009

recv slave msg len:25
Hold Registers[0~9]:0x0000 0x0001 0x0002 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009

recv slave msg len:25
Hold Registers[0~9]:0x0000 0x0001 0x0002 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009
```