Modbus RTU Relay 32CH

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Modbus RTU Relay 32CH
Modbus-rtu-relay-32ch-2.jpg

RS485
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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:

Modbus-RTU-Relay-32CH-details-7.jpg

  • 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.

Modbus-RTU-Relay-32CH-SSCOM-01.png

  • 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

L76X GPS Module rpi serial.png
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

Register address introduction

Address (HEX) Address storage content Register value Permission Modbus function code
0x0000
……
0x001F		 Daotong 1~Channel 32 relay address 0xFF00: relay on;
0x0000: relay off;
0x5500: relay flip;
 Read/write 0x01,0x05,0x0F
0x00FF Operate all relays 0xFF00: relays all on;
0x0000: relays all off;
0x5500: relays all flip;		 Write 0x05
0x0100
……
0x011F		 Daotong 1~Channel 32 relay flip address 0xFF00: Relay flips;
0x0000: Relay remains unchanged;
 Write 0x05,0x0F
0x01FF Operate all relays to flip 0xFF00: All relays flip;
0x0000: All relays remain unchanged;		 Write 0x05
0x0200
……
0x021F		 Relays of channel 1~channel 32 are open Delay time is data*100ms
Value: 0x0007, delay: 7*100MS = 700MS		 Write 0x05
0x0400
……
0x041F		 Relays of channel 1~channel 32 are closed Delay time is data*100ms
Value: 0x0007, delay: 7*100MS = 700MS		 Write 0x05
4x2000 Serial port parameters High eight bits are check mode: 0x00~0x02
Low eight bits are baud rate mode: 0x00~0x07		 Write 0x06
4x4000 Device address Directly store Modbus address
Device address: 0x0001		 Read 0x03,0x06
4x8000 Software version Convert to decimal and then shift the decimal point two places to the left to indicate the software version
0x0064 = 100 = V1.00		 Read 0x03

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

Software

Related application

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:
Serial Module FAQ01.png
Serial Module FAQ02.png

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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: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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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（Versions before November 2023） 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.
Modbus-32CH-hw-4R2.jpg

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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...

{{{5}}}


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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Question:What is the maximum power consumption (all relays activated)?

 Answer:

12V, 1.3A.

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Support



Technical Support

If you need technical support or have any feedback/review, please click the Submit Now button to submit a ticket, Our support team will check and reply to you within 1 to 2 working days. Please be patient as we make every effort to help you to resolve the issue.
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