Modbus RTU Relay 32CH

Modbus RTU Relay 32CH RS485

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Primary Attribute Category: {{{userDefinedInfo}}}: {{{userdefinedvalue}}} Brand: Waveshare

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Onboard Interfaces

Related Products

Overview

Safety Precautions

• This product must be operated and used by professional electricians or technical personnel. Please ensure electrical safety, including measures to prevent leakage and insulation during use.
• Before installing, maintaining, or replacing relay equipment, be sure to turn off the power and unplug the plug.
• Do not attempt to disassemble the relay to avoid damaging the equipment or causing electrical hazards.
• Please properly install and place the relay equipment product. Do not use it in damp, overheated, or flammable environments to avoid safety accidents caused by improper installation or use.

Hardware Test

RS485 Test

• Connect USB TO 485 and the target board with cables, and 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 send, plus check select ModbusCRC16 checksum, enter the first six bytes of the command and click send then the CRC checksum will be added automatically.

• For detailed control commands, please see the development protocol.

Demo Test

Note: RS485 cannot be directly connected to the serial port of the Raspberry Pi, as it may damage the device. A 485-level converter is required. It is recommended to use the Raspberry Pi with an RS485 CAN HAT module. For NUCLEO-F103RB and Arduino, it is recommended to use an RS485 CAN Shield module.

Raspberry Pi

Open the terminal of the Raspberry Pi, and input the following commands to enter the configure interface:

sudo raspi-config
Choose Interfacing Options -> Serial, disable shell visit, open the hardware serial port 

And then reboot the Raspberry Pi:

sudo reboot

Open /boot/config.txt file, and find the following configure sentences to enable the serial port. If there is none, you can add it at the end of the file:

enable_uart=1

For Raspberry Pi 3B users, the serial port is for Bluetooth, and you need to comment it out.

#dtoverlay=pi3-miniuart-bt

And then reboot the Raspberry Pi:

sudo reboot

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

sudo apt-get install unzip
wget https://files.waveshare.com/upload/7/74/Modbus_RTU_Relay_32CH_Code.zip
unzip Modbus_RTU_Relay_32CH_Code.zip
cd Modbus_RTU_Relay_32CH_Code/Python3
sudo python3 main.py

STM32

The STM32 demo is based on the NUCLEO-F103RB and the RS485 CAN Shield module.
Find the STM32 demo file directory and open the STM32 project. Make sure the keil5 software is installed on your computer before use, and download the demo to the development board.
Normal operation on the relay module will open and then close sequentially. The serial port will output the sent command.

Arduino

The Arduino demo is based on NUO PLUS and RS485 CAN Shield module.
Use Arduino IDE to open the demo and choose the corresponding development board to download the demo.
Normal operation on the relay module will open and then close sequentially. The serial port will output the sent command.

Development Protocol

Function Code

FUNC	NOTE
01	Read the relay status
03	Read the address and version
05	Write a single relay
06	Set the baud rate and address
0F	Write all relays

Single Relay Control

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

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
05	05 Command	Control the relay
00 00	Address	Register address of the relay to be controlled, 0x00 - 0x001F
FF 00	Command	0xFF00: relay on 0x0000: relay off 0x5500: relay flip
8C 3A	CRC16	CRC16 checksum of the first 6 bytes of data

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

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
05	05 Command	Control the relay
00 00	Address	Register address of the relay to be controlled, 0x0000-0x001F
FF 00	Command	0xFF00: relay on; 0x0000: relay off; 0x5500: relay flip
8C 3A	CRC16	CRC16 checksum of the first 6 bytes of data

For example: [NO. 1 address device]:
NO. 0 relay on: 01 05 00 00 FF 00 8C 3A
NO. 0 relay off: 01 05 00 00 00 00 CD CA
NO. 1 relay on: 01 05 00 01 FF 00 DD FA
NO. 1 relay off: 01 05 00 01 00 00 9C 0A
NO. 2 relay on: 01 05 00 02 FF 00 2D FA
NO. 2 relay off: 01 05 00 02 00 00 6C 0A
NO. 3 relay on: 01 05 00 03 FF 00 7C 3A
NO. 3 relay off: 01 05 00 03 00 00 3D CA
NO. 0 relay flip: 01 05 00 00 55 00 F2 9A
NO. 1 relay flip: 01 05 00 01 55 00 A3 5A
NO. 2 relay flip: 01 05 00 02 55 00 53 5A
NO. 3 relay flip: 01 05 00 03 55 00 02 9A

Control All Relays

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

Fields	Meaning	Note
01	Device Address	0x00 is the broadcast address; 0x01-0xFF is the device address
05	05 command	Control relay commands
00 FF	Address	Fixed 0x00FF
FF 00	Command	0xFF00: Relay on 0x0000: Relay off 0x5500: Relay flip
BC 0A	CRC16	CRC16 checksum of the first 6 bytes of data

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

Fields	Meaning	Code
01	Device Address	0x00 is the broadcast address; 0x01-0xFF indicates the device address
05	05 command	Control the relay commands
00 FF	Address	Fixed 0x00FF
FF 00	Commands	0xFF00: relay on 0x0000: relay off 0x5500: relay flip
BC 0A	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

[No. 1 address 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 flip: 01 05 00 FF 55 00 C2 AA

Read Relay Status

Sending code: 01 01 00 00 00 20 3D D2

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
01	01 Command	Query relay status command
00 00	Relay Start Address	Fixed 0x0000
00 10	Relay Numbers	Fixed 0x0020
3D D2	CRC16	CRC16 checksum of the first 6 bytes of data

Return code: 01 01 04 00 00 00 00 FB D1

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
01	01 Command	Query relay status command
02	Bytes	Returns all bytes of the status message
00 00 00 00	Query Status	Returned relay status Bit0: the first relay status; Bit1: the second relay status; Bit2: the third relay status; …… Bit31: the 32th relay status
FB D1	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

[NO.1 address device]

Send: 01 01 00 00 00 20 3D D2
Return: 01 01 04 00 00 00 00 FB D1 //All relays off
Send: 01 01 00 00 00 20 3D D2
Return: 01 01 04 00 00 00 01 3A 11 //NO.0 relay on, others off
Send: 01 01 00 00 00 20 3D D2
Return: 01 01 04 00 00 00 41 3B E1 //NO.0 and NO.6 relays on, others off

Write Relay Status

Sending code: 01 0F 00 00 00 20 04 FF FF FF FF C5 1C

Field	Meaning	Note
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
0F	0F Command	Write relay status command
00 00	Relay Start Address	Fixed 0x0000
00 20	Relay Numbers	Fixed 0x0020
04	Byte Number	Fixed 0x04
FF FF FF FF	Relay Status	Bit0: control the first relay; Bit1: control the second relay; Bit2: control the third relay; …… Bit31: control 31th relay;
C5 1C	CRC16	CRC16 checksum of the first 6 bytes of data

Return code: 01 0F 00 00 00 20 54 13

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
0F	0F Command	Control all relays command
00 00	Address	Fixed 0x0000
00 20	Relay Numbers	Fixed 0x0010
54 13	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

[No. 1 address device]

All relays on: 01 0F 00 00 00 20 04 FF FF FF FF C5 1C
All relays off: 01 0F 00 00 00 20 04 00 00 00 00 C4 88
0-1 on; 3-15 off: 01 0F 00 00 00 20 04 00 00 00 03 84 89

Relay Flash On Flash Off Command

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

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
05	05 Command	Single control command
02	Command	02 is a flash-on command, and 04 is a flash-off command.
00	Relay Address	address of the relay to be controlled, 0x00~0x1F
00 07	Interval Time	The delay time is data *100ms Value: 0x0007, Delay: 7*100MS = 700MS
8D B0	CRC16	CRC16 checksum of the first 6 bytes of data

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

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
05	05 Command	Single control command
02	Command	02 is a flash-on command, 04 is a flash-off command
00	Relay Address	To control the relay address, 0x00~0x1F
00 07	Interval Time	Delay time: data*100ms Value: 0x0007, delay: 7*100MS = 700MS
8D B0	CRC16	CRC16 checksum of the first 6 bytes of data

Remarks:

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

For example:

[NO.1 address device]

NO.0 relay flash on: 01 05 02 00 00 07 8D B0 //700MS = 7*100MS = 700MS
NO.1 relay flash on: 01 05 02 01 00 08 9C 74 //800MS
NO.0 relay flash off: 01 05 04 00 00 05 0C F9 //500MS
NO.1 relay flash off: 01 05 04 01 00 06 1D 38 //600MS

Baudrate Setting Command

Sending code: 00 06 20 00 00 05 43 D8

Fields	Meaning	Remarks
00	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
06	06 Command	Baudrate setting, device address
20 00	Command Register	0x2000 to set the baud rate, 0x4000 to set the device address
00	Parity	0x00 for no parity, 0x01 for even check, 0x02 for odd parity
05	Baudrate	Corresponding baudrate: 0x00: 4800 0x01: 9600 0x02: 19200 0x03: 38400 0x04: 57600 0x05: 115200 0x06: 128000 0x07: 256000
43 D8	CRC16	CRC16 checksum of the first 6 bytes of data

Return code: 00 06 20 00 00 05 43 D8

Fields	Meaning	Remarks
00	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
06	06 Command	set the baudrate and device address
20 00	Command Register	0x2000 is to set the baudrate, and 0x4000 is to set the device address
00	Parity	0x00 for broadcast address; 0x01-0xFF for device address
05	Baudrate	Corresponding baudrate: 0x00: 4800 0x01: 9600 0x02: 19200 0x03: 38400 0x04: 57600 0x05: 115200 0x06: 128000 0x07: 256000
43 D8	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

[NO.1 address 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

Device Address Setting Command

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

Fields	Meaning	Remarks
00	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
06	06 Command	Set the baudrate and device address
40 00	Command Register	0x2000 for setting the baudrate, 0x4000 for setting device address
00 01	Device Address	Set the device address, 0x0001-0x00FF
5C 1B	CRC16	CRC16 checksum of the first 6 bytes of data

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

Fields	Meaning	Remarks
00	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
06	06 Command	Set the baudrate and the device address
40 00	Command Register	0x2000 is for setting the baudrate, 0x4000 is for setting the device address
00 01	Device Address	Set the device address, 0x0001-0x00FF
5C 1B	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

[NO.1 address 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 the Device Address Command

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

Field	Meaning	Note
00	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
03	03 Command	read the device address command
40 00	Command Register	0x4000 for read device address, 0x8000 for read software version
00 01	Byte Numbers	Fixed 0x0001
90 1B	CRC16	CRC16 checksum of the first 6 bytes of data

Return code: 01 03 02 00 01 79 84

Field	Meaning	Remarks
00	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
03	03 Command	Read the software version and the device address
02	Bytes Number	Returned bytes
00 01	Device Address	Set the device address, 0x0001-0x00FF
79 84	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

[NO.1 address device]

Send: 00 03 40 00 00 01 90 1B
Return: 01 03 02 00 01 79 84 //Address: 0x01
[NO.2 address device]

Send: 00 03 40 00 00 01 90 1B
Return: 02 03 02 00 02 7D 85 //Address: 0x02
[NO.3 address device]

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

Read the Software Version Command

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

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address, 0x01-0xFF for device address
03	03 Command	Read software version, read device address command
80 00	Command Register	0x4000 for read device address, 0x8000 for read software version
00 01	Bytes	Fixed 0x0001
8F CA	CRC16	CRC16 checksum of the first 6 bytes of data

Return code: 01 03 02 00 64 B9 AF

Fields	Meaning	Remarks
01	Device Address	0x00 for broadcast address; 0x01-0xFF for device address
03	03 Command	Read the software version and the device address
02	Bytes Number	Returned bytes number
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
B9 AF	CRC16	CRC16 checksum of the first 6 bytes of data

For example:

Send: 00 03 80 00 00 01 AC 1B
Return: 01 03 02 00 64 B9 AF //0x0064 = 100 =V1.00

Resource

Demo

• Demo

Software

• SSCOM

Related application

• Using Modbus RTU Relay with Homeassistant

FAQ

Question:It doesn't work on non-windows systems, how can I fix it?

 Answer:

Click here to install the corresponding drivers.

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Question:Does it support Linux system?

 Answer:

Yes, it also supports Win7/8/8.1/10/11, Mac, Linux, Android, and WinC...

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Question:What about the RS485 proximity communication exception, the received data will be more than 0?

 Answer:

Remove the 120-ohm termination matching resistor for RS485.

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Question:What interfaces are supported for mutual conversion?

 Answer:

• Support USB to RS232, RS485 or TTL;
• Does not support RS232, RS485, TTL simultaneous conversion to USB
• RS232, RS485 and TTL cannot be converted to each other

Question:Does it support RS232,RS485 and TTL interchange?

 Answer:

Not supported, RS232, RS485 and TTL can not be interchangeable, support USB to RS232, RS485, or TTL.

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Question:How can I confirm that the TTL, RS232 or RS485 function is working?

 Answer:

TTL and RS232 are full-duplex communication, you can short RXD and TXD to test, RS485 is half-duplex communication, you can test with an external USB to RS485 device, the following figure is the loopback test TTL:

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Question:What is the VCC function?

 Answer:

VCC is the power supply pin, which can be switched by 5V or 3.3V (50mA) to power the connected device, if the device already has another external power supply, it can be connected without VCC.

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Question:Does it support node configuration? Does it support Modbus?

 Answer:

• The module is only for interface switch in terms of hardware, it does not support Modbus. It supports connecting to Modbus devices with an onboard RS485 (RS232, TTL) interface.
• When learning the Modbus protocol, you need to understand Modbus's function code and data format. Modbus has a variety of function codes, each of which corresponds to one type of operation, such as reading the coil status, reading the input status, reading the holding register, and so on.

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Question:Should the RS485 communication connect to GND?

 Answer:

No, but it is more stable with a connection to GND. For better performance, reliability, and anti-interference, it is recommended to connecting to GND for a long-distance communication.

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Question:When I use 24V power supply and use more than 8 channels at the same time, Relay will automatically shut down after working for a period of time.

 Answer:

This is caused by our old version setting the module current limiting resistor too large. If you encounter this problem during use, you can contact customer service to send it back for a new version, or you can disassemble the casing yourself and change the resistance to 5.1R or 4.7R, or short-circuit it directly to fix this problem, as shown in the figure below.

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Question:Does it support Linux system?

 Answer:

Yes, it also supports Win7/8/8.1/10/11, Mac, Linux, Android, and WinC...

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Question:What about the RS485 proximity communication exception, the received data will be more than 0?

 Answer:

Remove the 120-ohm termination matching resistor for RS485.

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Question:Since I'm having difficulties calculating the CRC16. do you have perhaps a well-documented Python example?

 Answer:

If you want to calculate easily CRC16 Modbus then you can check this 3rd Party site: https://www.lammertbies.nl/comm/info/crc-calculation.

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