Modbus RTU Analog Output 8CH
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Overview
Hardware Description
- AO1~AO8 is the analog output, AGND is the analog ground, and the output range is 0-20mA.
Please note that the output current is related to the input voltage and the load, and if the input voltage is insufficient, the output current will be insufficient.
For example: if the internal sampling resistance is 100R, the external load is 500R with an output of 20mA, and the voltage is (100R+500R)*20mA=12V. Additionally, considering a 2V internal voltage drop, the input needs to be a minimum of 14V to achieve an output of 20mA.
Version Comparision
Currently, the analog output has two versions: the current output version and the voltage output.
- Modbus RTU Analog Output 8CH outputs the current with the range of 0-20mA.
- Modbus RTU Analog Output 8CH (B) outputs the voltage with the range of 0-10V.
Hardware Connection
- Connect the USB TO 485 and the target board through dupont line, connects A --> A and B --> B as shown below:
Software Test
SSCOM
- Download SSCOM and open it on the PC, open the corresponding port, set the baud rate of 9600, and select hex to send and receive.
Send the following commands, channel 1 will then output 1mA of current.
01 06 00 00 03 E8 89 74
- If you need to send other commands then select HEX to 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 example, send the following command to set channel 1 to output 5mA current.
01 06 00 00 13 88
- For more details, you can see the development protocol.
Modbus Poll Software
- It is not convenient to observe data through the SSCOM software. You can use Modbus Poll software to read data. Download and install Modbus Poll software.
- Open the software, and select 'Setup -> Read/Write Definition'. Choose the actual device address for Slave ID, select 16 Write Multiple Registers in Function, and change the Quantity to 8 channels. Click "OK" to confirm.
- Select Connection -> Connect..., and choose the corresponding serial port, the baud rate as 9600, 8 Data bits, none parity mode. Click "OK" to connect.
- After the connection is normal then you can set 1-8 channels analog output current, unit uA, range 0-20000uA, i.e. 0-20mA.
Demo Test
Note: RS485 cannot be directly connected to the Raspberry Pi's serial port; otherwise, the device may be burned. It requires a 485 level converter. It's advisable to use the RS485 CAN HAT with the Raspberry Pi. For NUCLEO-F103RB and Arduino, it's recommended to use with the RS485 CAN Shield module.
Raspberry Pi
Enter the Raspberry Pi terminal and input the following commands to enter the configure interface:
sudo raspi-config Select Interfacing Options -> Serial Port, Select Yes, and Open the hardware serial port
And then reboot the Raspberry Pi:
sudo reboot
Insert the RS485 CAN HAT module into the Raspberry Pi, and connect A and B of ModBus RTU Relay module and RS485 CAN HAT module.
If you are using other 485 devices, make sure the connection is A-A, B-B.
Run the following command to run the demo:
sudo apt-get install unzip sudo apt-get install python3-pip pip install modbus_tk wget https://files.waveshare.com/wiki/Modbus-RTU-Analog-Output-8CH/Modbus_RTU_Analog_Output_Code.zip unzip Modbus_RTU_Analog_Output_Code.zip cd Modbus_RTU_Analog_Output_Code/Python3 sudo python3 modbus.py
After the demo runs normally, all channels will output 5mA current.
STM32
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. Note that before use make sure the computer has installed keil5 software, and download the demo to the development board.
After the demo runs normally, all channels will output 5mA current.
Arduino
The Arduino demo is based on NUO PLUS and RS485 CAN Shield module.
Use Arduino IDE to open the demo, select the corresponding development board, and then download the demo.
After the demo runs normally, all channels will output 5mA current.
Development Protocol
Function Code Introduction
| Function Code | Note |
|---|---|
| 03 | Read Holding Registers |
| 06 | Write Single Holding Register |
| 10 | Write Multiple Holding Register |
Register Address Introduction
| Address (HEX) | Address Storage Content | Register Value | Permissions | Modbus Function Code |
|---|---|---|---|---|
| 4x0000 …… 4x0007 |
Channel 1 ~ 8 Output Data | Unsigned hexadecimal | Read/Write | 0x03, 0x06, 0x10 |
| 4x2000 | Serial port parameters | High 8-bit is the parity mode: 0x00~0x02 Low 8-bit is the baud rate mode: 0x00~0x07 |
Read/Write | 0x03, 0x06 |
| 4x4000 | Device address | Direct store Modbus addresses Device address: 0x0001-0x00FF |
Read/Write | 0x03, 0x06 |
| 4x8000 | Software version | Convert to decimal and then shift the decimal point two places to the left to represent the software version 0x0064 = 100 = V1.00 |
Read | 0x03 |
Set Single-channel Output Command
Send code: 01 06 00 00 03 E8 89 74
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 06 | 06 Command | Write a single register command |
| 00 00 | Register Address | 0x0000 - 0x0007 corresponds to 1~8 channel output data |
| 03 E8 | Value Setting | Set the value to hexadecimal, unit uA, high bits in the front, low bits at the end 0x03E8 = 1000uA, or 1mA |
| 89 74 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Receive code: 01 06 00 00 03 E8 89 74
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 06 | 06 Command | Write a single register command |
| 00 00 | Register Address | 0x0000 - 0x0007 corresponds to 1~8 input channel data type |
| 03 E8 | Value Setting | Set the value in hexadecimal, unit mV, high bits in the front, low bits in the end. 0x03E8 = 1000mV, or 1V |
| 89 74 | CRC16 | CRC16 checksum of the first 6 bytes of data |
For example:
[No.1 address device]
Set channel 1 output 1mA : 01 06 00 00 03 E8 89 74
Read channel 2 output 5mA : 01 06 00 01 13 88 D5 5C
Set Multiple-channel Output Command
Send code: 01 10 00 00 00 08 10 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 3C 05
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates the device address |
| 10 | 10 Command | Write multi-register command |
| 00 00 | Register Initial Address | 0x0000 - 0x0007 corresponds to 1~8 output channels |
| 00 08 | Register Numbers | Set the number of registers, up to 8 channels |
| 10 | Bytes Numbers | Set the output bytes |
| 03 E8 …… 03 E8 |
Command | Channel 1 analog output …… Channel 8 analog output Set the value in hexadecimal, unit in mV, high bits in the front, low bits in the end 0x03E8 = 1000uA, or 1mA |
| 3C 05 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Receive code: 01 10 00 00 00 08 C1 CF
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 10 | 10 Command | Write multi-register command |
| 00 00 | Register Initial Address | 0x0000 - 0x0007 corresponds to 1~8 output channels |
| 00 08 | Register Numbers | Set the register numbers, up to 8 channels |
| C1 CF | CRC16 | CRC16 checksum of the first 6 bytes of data |
For example:
[No.1 address device]
Set channel 1-8 output 1mA: 01 10 00 00 00 08 10 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 3C 05
Set channel 3-5 output 2mA: 01 10 00 02 00 03 06 07 D0 07 D0 07 D0 84 0E
Read Channel Output Command
Send code: 01 03 00 00 00 08 44 0C
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 03 | 03 Command | Read holding register |
| 00 00 | Register Initial Address | 0x0000 - 0x0007 corresponds to 1~8 input channels |
| 00 08 | Register Numbers | Read the register numbers, up to 8 channels |
| 44 0C | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return code: 01 03 10 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 03 E8 C1 91
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 03 | 03 Command | Read holding register |
| 10 | Byte Numbers | Number of bytes for returning status information |
| 03 E8 …… 03 E8 |
Output Value | Channel 1 analog output …… Channel 8 analog output Set the value in hexadecimal, unit mV, high bits in the front, low bits in the end 0x03E8 = 1000uA, or 1mA |
| C1 91 | CRC16 | CRC16 checksum of the first 6 bytes of data |
For example
[No.1 address device]
Read channel 1-8 data type: 01 03 00 00 00 08 44 0C
Read channel 1 data type: 01 03 00 00 00 01 84 0A
Read channel 2 data type: 01 03 00 01 00 01 D5 CA
Read channel 3-5 data type: 01 03 00 02 00 03 A4 0B
Set Baudrate Command
Send code: 00 06 20 00 00 05 43 D8
| Fields | Description | Note |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 06 | 06 Command | Set the baud rate and device addresses |
| 20 00 | Command Register | 0x2000 for setting baudrate, 0x4000 for setting device addresses |
| 00 | Parity Method | 0x00 is no parity, 0x01 is even parity, 0x02 is odd parity |
| 05 | Baudrate Value | The baud rate values correspond: 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 | Description | Note |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 06 | 06 Command | Set the baud rate and device addresses |
| 20 00 | Command Register | 0x2000 is setting the baud rate, 0x4000 is setting the device address |
| 00 | Parity Method | 0x00 is no parity, 0x01 is even parity, 0x02 is odd parity |
| 05 | Baudrate | The baud rate values correspond: 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 baud rate 4800: 00 06 20 00 00 00 83 DB
Set baud rate 9600: 00 06 20 00 00 01 42 1B
Set baud rate 115200: 00 06 20 00 00 05 43 D8
Set Device Address Command
Sending code: 00 06 40 00 00 01 5C 1B
| Fields | Description | Note |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 06 | 06 Command | Set the baud rate and device addresses |
| 40 00 | Command Register | 0x2000 is setting baudrate, 0x4000 is 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 |
Return code: 00 06 40 00 00 01 5C 1B
| Fields | Description | Note |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 06 | 06 Command | Set the baud rate and device addresses |
| 40 00 | Command Register | 0x2000 is setting baudrate, 0x4000 is 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 Device Address Command
Send code: 00 03 40 00 00 01 90 1B
| Fields | Description | Note |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 03 | 03 Command | Read 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 |
Received code: 01 03 02 00 01 79 84
| Fields | Description | Note |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates device address |
| 03 | 03 Command | Read the software version and the device address |
| 02 | Byte Numbers | Return byte numbers |
| 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
Receive: 01 03 02 00 01 79 84 //address 0x01
[No.2 address device]
Send: 00 03 40 00 00 01 90 1B
Receive: 02 03 02 00 02 7D 85 //address 0x02
[No.3 address device]
Send: 00 03 40 00 00 01 90 1B
Receive: 03 03 02 00 03 81 85 //address 0x03
Read Software Version Command
Sending code: 00 03 80 00 00 01 AC 1B
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 03 | 03 Command | Read the software version and the device address |
| 80 00 | Command Register | 0x4000 is reading device address, 0x8000 is reading software version |
| 00 01 | Byte Numbers | Fixed 0x0001 |
| 8F CA | CRC16 | CRC16 checksum of the first 6 bytes of data |
Receive code: 01 03 02 00 64 B9 AF
| Fields | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address; 0x01-0xFF indicates device address |
| 03 | 03 Command | Read the software version and the device address |
| 02 | Byte Numbers | Received Byte Numbers |
| 00 64 | Software Version | Convert to decimal and then shift the decimal point two places to the left to represent the software version. 0x0064 = 100 = V1.00 |
| B9 AF | CRC16 | CRC16 checksum of the first 6 bytes of data |
For example:
[No.1 address device]
Send: 00 03 80 00 00 01 AC 1B
Receive: 01 03 02 00 64 B9 AF //0x0064 = 100 =V1.00
Resource
Demo
Software
FAQ
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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