Modbus RTU Relay (D)

RS485 Relay Module, Digital Input
RS485

Overview

Electrical Safety Precautions

This product should be operated and used by professional electricians or technical personnel. Please ensure electrical safety measures are in place, including protection against leakage and insulation.
Before installing, maintaining, or replacing relay equipment, always turn off the power and unplug the plug.
Do not attempt to dismantle relay equipment to avoid damaging the device or risking electric shock.
Please properly install and place relay equipment. Avoid use in damp, overheated, or flammable environments to prevent accidents caused by improper installation or use.

This is an industrial 8-channel relay module controlled via RS485 bus, with 8-ch digital input, utilizing Modbus RTU protocol. It features embedded protection circuits such as power isolation, magnetical isolation, TVS, etc. It also comes with an ABS enclosure. The Modbus RTU Relay (D) is very easy to use. Due to its fast communication, stability, reliability, and safety, it is an ideal choice for industrial control equipment and applications with high communication requirements.

Parameters

Power Supply	DC 7~36V
Communication Interface	RS485
Baudrate	4800, 9600, 19200, 38400, 57600, 115200, 128000, 256000
Default Communication Format	9600, N, 8, 1
Relay Channels	8 Channels
Contact Form	1NO, 1NC
Contact Load	≤10A 250V AC or ≤10A 30V DC
Digital Input	8DI, 5~36V, passive/active input (NPN or PNP), built-in bi-directional optocoupler
Modbus Protocol	Standard Modbus RTU protocol
RS485 Address Setting	1~255
Indicator	STA: MCU indicator, keep flashing when MCU normally working TXD: Transmit Data indicator, lights up when sending data RXD: Receive Data indicator, lights up when receiving data.

Primary Functions

Supports reading digital input by sending Modbus RTU protocol commands, and can control relay output based on input.

Wiring Description

DI1-DI8 is the 8-channel signal input terminal, and DGND is the ground signal. COM is the common terminal for the input signal, it can be NC(Not Connected), connected to the positive or negative of the power supply, directly powered from the power supply or connected to an independent power supply.
NC: dry contact passive input.
Connect to the power supply positive: low active, NPN wet contact active input, voltage: 5V-30V DC.
Connect to the power supply negative: high active, PNP wet contact active input.

Digital Input Wiring

Passive Dry Contact Wiring

Passive dry contact input:

Active Wet Contact Wiring

Active wet contact NPN input

Active wet contact PNP input

Relay Output Wiring

The device comes with a relay with a contact capacity of 10A 250V AC or 10A 30V DC, which allows direct control of household 220V AC equipment or DC equipment up to 30V.

Dimensions

Hardware Test

RS485 Test

Connect the USB TO 485 to the target board through wires, connect A-A and B-B as shown below:

Download SSCOM and open it on the computer, open the corresponding port number, and set the baud rate as 9600. Clicking on multiple strings will open multiple string-sending windows. Clicking on the corresponding function will send the corresponding command.

If you need to send other commands then select HEX to send, verify select ModbusCRC16 check, enter the first six bytes of the command, and click send then the CRC check code will be added automatically.
For detailed control commands, please see the development protocol.

Demo Test

Note: RS485 can not be directly connected to the serial port of the Raspberry Pi, otherwise it may burn the device, you need to add 485 level conversion. For Raspberry Pi, it is recommended to work with the RS485 CAN HAT module. For NUCLEO-F103RB and Arduino, it is recommended to work with the RS485 CAN Shield module.

Raspberry Pi

Open the Raspberry Pi terminal and input the following commands to enter the configuration interface.

sudo raspi-config
Select Interfacing Options -> Serial Port, select Yes to open the hardware serial port

And then reboot the Raspberry Pi:

sudo reboot

Insert the RS485 CAN HAT into the Raspberry Pi, and connect the Modbus RTU Relay module to the RS485 CAN HAT through A and B.
If you are using other 485 devices, you need to make sure A-A, B-B.
Run the following commands:

sudo apt-get install unzip
wget https://files.waveshare.com/wiki/Modbus-RTU-Relay-(D)/Modbus_RTU_Relay_D_Code.zip
unzip Modbus_RTU_Relay_D_Code.zip
cd Modbus_RTU_IO_Code/Python3
sudo python3 main.py

After the demo normally runs, each channel can be opened and closed in order, and the current input status is displayed.

STM32

The STM32 demo is based on the NUCLEO-F103RB and RS485 CAN Shield module.
Find the STM32 demo file directory and open the STM32 project. Please note that the keil5 software is installed before use, and download the demos to the development board.
After running normally, each channel can opened and closed in order. The serial port will output the commands to be sent and finally display the current input status.

Arduino

The Arduino demo is based on the UNO PLUS and RS485 CAN Shield module.
Use the Arduino IDE to open the demo, select the corresponding development board, and download the demos.
After running normally, each channel will open and close in order. The serial port will output the commands to be sent and finally display the current input status.

Development Protocol

Function Code Introduction

Function Code	Description
01	Read output status
02	Read input status
03	Read save register
05	Write single relay
06	Set single register
0F	Write multiple relays
10	Set multiple registers

Register Address Introduction

Address（HEX）	Address storage content	Register value	Permission	Modbus Function Code
0x0000 …… 0x0007	Channel 1~8 relay address	0xFF00: relay on 0x0000: relay off 0x5500: relay toggle	Read/Write	0x01, 0x05, 0x0F
0x00FF	Control All Registers	0xFF00: all relays on 0x0000: all relays off 0x5500: all relays toggle	Write	0x05
0x0200 …… 0x0207	Channel 1~8 relay flash on	Interval time: data100ms Value: 0x0007, Interval time: 7100MS = 700MS	Write	0x05
0x0400 …… 0x0407	Channel 1~8 relay flash off	Interval time: data100ms Value: 0x0007, Interval time: 7100MS = 700MS	Write	0x05
1x0000 …… 1x0007	Channel 1~8 input address	Indicates channel 0~8 input channel status	Read	0x02
4x1000 …… 4x1007	Channel 1~8 relay control mode	0x0000~0x0002 control mode	Read/Write	0x03, 0x06, 0x10
4x2000	UART Parameters	The high eight bits indicate the parity mode: 0x00~0x02 The low eight bits indicate the baud rate mode: 0x00~0x07	Write	0x06
4x4000	Device Address	Directly store Modbus address Device address: 0x0001-0x00FF	Read/Write	0x03, 0x06
4x8000	Software Version	Converting to decimal and then shifting the decimal point two places to the left will represent the software version 0x0064 = 100 = V1.00	Read	0x03

Read Relay Control Mode

Send code: 01 03 10 00 00 08 40 CC

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
03	03 Commad	Read Holding Register
10 00	Register Start Address	0x1000 - 0x1007 corresponds to 1~8 input channels
00 08	Register Numbers	Read register numbers, up to 8 channels
40 CC	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 03 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 E4 59

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
03	03 Commad	Read Holding Register
10	Byte Numbers	Returns all bytes of the status message
00 00 …… 00 00	Control Mode	Indicates relay 1 - 8 control mode, 0x0000~0x0002 indicate three control modes 0x0000: Normal mode, the relay is directly controlled by commands; 0x0001: Linkage mode, relay status is the same as the corresponding input channel status; 0x0002: Toggle mode, the corresponding relay toggles once when the input channel inputs a pulse.
E4 59	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Read relay 1-8 control mode: 01 03 10 00 00 08 40 CC
Read relay 1 control mode: 01 03 10 00 00 01 80 CA
Read relay 2 control mode: 01 03 10 01 00 01 D1 0A
Read relay 3-5 control mode: 01 03 10 02 00 03 A0 CB

Single Relay Relay Control Mode

Send code: 01 06 10 00 00 01 4C CA

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
06	06 Command	Write single register
10 00	Register Start Address	0x1000 - 0x1007 corresponds to 1~8 input channels
00 01	Control Mode	Indicates relay 1 - 8 control mode, 0x0000~0x0002 indicate three control modes 0x0000: Normal mode, the relay is directly controlled by commands; 0x0001: Linkage mode, relay status is the same as the corresponding input channel status; 0x0002: Toggle mode, input channel input a pulse corresponding to the relay state toggles once.
4C CA	CRC16	The CRC16 checksum of the first 6 bytes of data

Note: All modes except linkage mode support relay control by command.

Receive code: 01 06 10 00 00 01 4C CA

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
06	06 Command	Write single register
10 00	Register Start Address	0x1000 - 0x1007 corresponds to 1~8 input channels
00 01	Control Mode	Indicates relay control mode, 0x0000~0x0002 indicate three control modes
4C CA	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Set relay 1 as linkage mode: 01 06 10 00 00 01 4C CA
Set relay 2 as toggle mode: 01 06 10 01 00 02 5D 0B

Set Multiple Relay Control Mode

Send code: 01 10 10 00 00 08 10 00 01 00 01 00 01 00 01 00 01 00 01 00 01 00 01 7C B1

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
10	10 Command	Write Multiple Register
10 00	Register Start Address	0x1000 - 0x1007 corresponds to 1~8 input channels
00 08	Register Numbers	Set register numbers, up to 8 channels
10	Byte Numbers	Set output bytes
00 01 …… 00 01	Control Mode	Indicates relay 1 - 8 control mode, 0x0000~0x0002 indicate three control modes 0x0000: Normal mode, the relay is directly controlled by commands; 0x0001: linkage mode, relay status is the same as the corresponding input channel status; 0x0002: toggle mode, input channel input a pulse corresponding to the relay state toggles once.
7C B1	CRC16	The CRC16 checksum of the first 6 bytes of data

Note: All modes except linkage mode support relay control by command.

Receive code: 01 10 10 00 00 08 C5 0F

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
10	10 Command	Write Multiple Registers
10 00	Register Start Address	0x1000 - 0x1007 Corresponds to channel 1~8 relay control mode
00 08	Register Numbers	Set register numbers, up to 8 channels
C5 0F	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Set channel 1-8 relay as normal mode: 01 10 10 00 00 08 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0B 5C
Set channel 1-8 relay as linkage mode: 01 10 10 00 00 08 10 00 01 00 01 00 01 00 01 00 01 00 01 00 01 00 01 7C B1
Set channel 3-5 relay as toggle mode: 01 10 10 02 00 03 06 00 02 00 02 00 02 4A 4B

Single Relay Control

Send code: 01 05 00 00 FF 00 8C 3A

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
05	05 Command	Relay control
00 00	Address	The register address of relays to be controlled, 0x0000 - 0x0008
FF 00	Command	0xFF00: Relay on 0x0000: Relay off 0x5500: Relay toggle
8C 3A	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 05 00 00 FF 00 8C 3A

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
05	05 Command	Relay control
00 00	Address	The register address of relays to be controlled, 0x0000-0x0008
FF 00	Command	0xFF00: Relay on 0x0000: Relay off 0x5500: Relay toggle
8C 3A	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Relay 0 on: 01 05 00 00 FF 00 8C 3A
Relay 0 off: 01 05 00 00 00 00 CD CA
Relay 1 on: 01 05 00 01 FF 00 DD FA
Relay 1 off: 01 05 00 01 00 00 9C 0A
Relay 2 on: 01 05 00 02 FF 00 2D FA
Relay 2 off: 01 05 00 02 00 00 6C 0A
Relay 3 on: 01 05 00 03 FF 00 7C 3A
Relay 3 off: 01 05 00 03 00 00 3D CA
Relay 0 toggle: 01 05 00 00 55 00 F2 9A
Relay 1 toggle: 01 05 00 01 55 00 A3 5A
Relay 2 toggle: 01 05 00 02 55 00 53 5A
Relay 3 toggle: 01 05 00 03 55 00 02 9A

Control All Relays

Send code: 01 05 00 FF FF 00 BC 0A

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
05	05 Command	Relay control
00 FF	Address	Fixed 0x00FF
FF 00	Command	0xFF00: Relay on 0x0000: Relay off 0x5500: Relay toggle
BC 0A	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 05 00 FF FF 00 BC 0A

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
05	05 Command	Relay control
00 FF	Address	Fixed 0x00FF
FF 00	Command	0xFF00: Relay on 0x0000: Relay off 0x5500: Relay toggle
BC 0A	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

All relays on: 01 05 00 FF FF 00 BC 0A
All relays off: 01 05 00 FF 00 00 FD FA
All relays toggle: 01 05 00 FF 55 00 C2 AA

Read Relay Status

Send code: 01 01 00 00 00 08 3D CC

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
01	01 Command	Query relay status
00 00	Relay Start Address	Fixed 0x0000
00 08	Relay Numbers	Fixed 0x0008
3D CC	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 01 01 00 51 88

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
01	01 Command	Query relay status
01	Byte Numbers	Returns all bytes of the status message
00	Query Status	Received relay status Bit0: the first relay status; Bit1: the second relay status; Bit2: the third relay status; …… Bit7: the eighth relay status
51 88	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Send: 01 01 00 00 00 08 3D CC
Receive: 01 01 01 00 51 88 //all relays off
Send: 01 01 00 00 00 08 3D CC
Receive: 01 01 01 01 90 48 //Relay 0 is on, others are off
Send: 01 01 00 00 00 08 3D CC
Receive: 01 01 01 41 91 B8 //Relay 0 and 6 are on, others are off

Write Relay Status

Send code: 01 0F 00 00 00 08 01 FF BE D5

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
0F	0F Command	Write relay status
00 00	Relay Start Address	Fixed 0x0000
00 08	Relay Numbers	Fixed 0x0008
01	Byte Numbers	Fixed 0x01
FF	Relay Status	Bit0: Control the first relay; Bit1: Control the second relay; Bit2: Control the third relay; …… Bit7: Control the eighth relay
BE D5	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 0F 00 00 00 01 94 0B

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
0F	0F Command	Control all register
00 00	Address	Fixed 0x0000
00 08	Relay Numbers	Fixed 0x0008
54 0D	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

All relays on: 01 0F 00 00 00 08 01 FF BE D5
All relays off: 01 0F 00 00 00 08 01 00 FE 95
0-1 on; 3-7 off: 01 0F 00 00 00 08 01 03 BE 94

Relay Flash ON/OFF Command

Send code: 01 05 02 00 00 07 8D B0

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
05	05 Command	Single control command
02	Command	02: flash on, 04: flash off
00	Relay Address	The relay address to be controlled, 0x00~0x08
00 07	Interval Time	The interval time: data100ms Value: 0x0007, Interval time: 7100MS = 700MS
8D B0	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 05 02 00 00 07 8D B0

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
05	05 Command	Single control command
02	Command	02: flash on; 04: flash off
00	Relay Address	The relay address to be controlled, 0x00~0x08
00 07	Interval time	the interval time: data100ms Value: 0x0007, Interval time: 7100MS = 700MS
8D B0	CRC16	The CRC16 checksum of the first 6 bytes of data

Note:

The maximum setting for the flash-on flash-off time is 0x7FFF.

For example:

[Address 1 device]:

Relay 0 flash on: 01 05 02 00 00 07 8D B0 //700MS = 7*100MS = 700MS
Relay 1 flash on: 01 05 02 01 00 08 9C 74 //800MS
Relay 0 flash off: 01 05 04 00 00 05 0C F9 //500MS
Relay 0 flash off: 01 05 04 01 00 06 1D 38 //600MS

Read Input Status

Send code: 01 02 00 00 00 08 79 CC

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address.
02	02 Command	Read input status
00 00	Relay Start Address	Fixed 0x0000
00 08	Register Numbers	Fixed 0x0008
79 CC	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 02 01 00 A1 88

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address.
02	02 Command	Read input status command
01	Relay Numbers	Returns all bytes of the status message
00	Query status	Return relay status Bit0: channel 1 input status; Bit1: channel 2 input status Bit2: channel 3 input status …… Bit7: channel 8 input status
A1 88	CRC16	The CRC16 checksum of the first 6 bytes of data.

For example:

[Address 1 device]:

Send: 01 02 00 00 00 08 79 CC
Receive: 01 01 01 00 51 88 //Inputs are all untriggered
Send: 01 02 00 00 00 08 79 CC
Receive: 01 02 01 01 60 48 //Channel 1 input is triggered, and the rest of channels are not triggered.
Send: 01 02 00 00 00 08 79 CC
Receive: 01 02 01 41 61 B8 //Channel 1 and 7 input are triggered, and the rest of channels are not triggered.

Baudrate Setting Command

Send code: 00 06 20 00 00 05 43 D8

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
06	06 Command	Set the baudrate and device address
20 00	Command Register	0x2000: set the baud rate; 0x4000: set the device address, 0x8000: read software version
00	Parity Method	0x00: no parity, 0x01: even parity; 0x02: odd parity
05	Baud Rate Value	Corresponding baud rate 0x00: 4800 0x01: 9600 0x02: 19200 0x03: 38400 0x04: 57600 0x05: 115200 0x06: 128000 0x07: 256000
43 D8	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 00 06 20 00 00 05 43 D8

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
06	06 Command	Set the baud rate and device address
20 00	Command Register	0x2000: set the baud rate, 0x4000: set the device address, 0x8000: read the software version
00	Parity Method	0x00: no parity, 0x01: odd parity, 0x02: even parity
05	Baud Rate	Corresponding baud rate 0x00: 4800 0x01: 9600 0x02: 19200 0x03: 38400 0x04: 57600 0x05: 115200 0x06: 128000 0x07: 256000
43 D8	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Set the baudrate as 4800: 00 06 20 00 00 00 83 DB
Set the baudrate as 9600: 00 06 20 00 00 01 42 1B
Set the baudrate as 115200: 00 06 20 00 00 05 43 D8

Set the Device Address Command

Send code: 00 06 40 00 00 01 5C 1B

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
06	06 Command	Set the baud rate and device address
40 00	Command Register	0x2000: set the baudrate, 0x4000: set the device address, 0x8000: read the software version
00 01	Device Address	Set the device address, 0x0001-0x00FF
5C 1B	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 00 06 40 00 00 01 5C 1B

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
06	06 Command	Set the baud rate and device address
40 00	Command Register	0x2000: set the baud rate, 0x4000: set the device address, 0x8000: read the software version
00 01	Device Address	Set the device Address, 0x0001-0x00FF
5C 1B	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Set the device address as 0x01: 00 06 40 00 00 01 5C 1b
Set the device address as 0x02: 00 06 40 00 00 02 1C 1A
Set the device address as 0x03: 00 06 40 00 00 03 DD DA

Read Device Address Command

Send code: 00 03 40 00 00 01 90 1B

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
03	03 Command	Read the device address
40 00	Command Register	0x2000: set the baud rate, 0x4000: set the device address, 0x8000: read the software version
00 01	Byte Numbers	Fixed 0x0001
90 1B	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 03 02 00 01 79 84

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
03	03 Command	Read the software version and device address
02	Byte Numbers	Return bytes
00 01	Device Address	The device address to be set, 0x0001-0x00FF
79 84	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

[Address 1 device]:

Send: 00 03 40 00 00 01 90 1B
Receive: 01 03 02 00 01 79 84 //Address: 0x01
[Address 2 device]:

Send: 00 03 40 00 00 01 90 1B
Receive: 02 03 02 00 02 7D 85 //Address: 0x02
[Address 3 device]:

Send: 00 03 40 00 00 01 90 1B
Receive: 03 03 02 00 03 81 85 //Address: 0x03

Read Software Version Command

Send code: 00 03 80 00 00 01 AC 1B

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
03	03 Command	Read the software version and device address
80 00	Command Register	0x2000: set the baud rate, 0x4000: set the device address, 0x8000: read the software version
00 01	Byte Numbers	Fixed 0x0001
8F CA	CRC16	The CRC16 checksum of the first 6 bytes of data

Receive code: 01 03 02 00 64 B9 AF

Field	Description	Note
01	Device Address	0x00 indicates the broadcast address, 0x01-0xFF indicates the device address
03	03 Command	Read the software version and device address
02	Byte Numbers	Received Byte Numbers
00 64	Software version	Converting to decimal and shifting the decimal point two places to the left indicates the software version. 0x0064=100=V1.00
F0 B8	CRC16	The CRC16 checksum of the first 6 bytes of data

For example:

Send: 00 03 80 00 00 01 AC 1B
Receive: 03 03 02 00 C8 F1 00 //0x00C8 = 200 =V2.00

Resource

Demo

Demo code

Software

SSCOM

Firmware

Firmware

FAQ

Question:I sent a command to control the relay, but it didn’t respond. What could be the issue??

Answer:

The command must be sent in hex format with a CRC checksum.

1、If the module does not respond to the command, verify that the baud rate and device ID are correct. You may also try Restoring the factory settings.
2、If the above steps do not resolve the issue, please submit a ticket to contact the Waveshare technical support team.

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Support

Technical Support

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