Modbus RTU Analog Output 8CH
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Overview
Hardware Description
- AON is the analog output terminal, AGND is the analog ground, and the output range is 0-20mA.
Note: The output current depends on the input voltage and load size. If the input voltage is insufficient, it may result in inadequate output current.
For example: If the internal sampling resistor is 100R and the external load is 500R, with an output of 20mA, the voltage is (100R + 500R) * 20mA = 12V. Additionally, there is a 2V internal voltage drop, so the input must be at least 14V to output 20mA.
Version Comparision
Currently, there are two versions of the analog output series, one defaults to current output, and the other defaults to voltage output.
- Modbus RTU Analog Output 8CH outputs current, range 0-20mA
- Modbus RTU Analog Output 8CH (B) outputs voltage, range 0-10V
Hardware Connection
- Connect the USB TO 485 to the target boards via cables, A-A and B-B connected as shown below:
Software Test
SSCOM Serial Port Debugging Assistant
- Download SSCOM serial port debugging assistant and open it on the computer. Open the corresponding port number, set the baud rate as 9600, and select SendHEX and HEXshow.
Send the following command, and channel 1 will output 1mA current under normal circumstances.
01 06 00 00 03 E8 89 74
- If you need to send other commands, choose SendHEX. For checksum validation, select ModbusCRC16. After entering the first six bytes of the command, clicking SEND will automatically add the CRC check code.
For example, send the following command, you can set channel 1 to output 5mA current.
01 06 00 00 13 88
- For more control commands, you can refer to the development protocol.
Modbus Poll Software
- It is not convenient to use the SSCOM software for observing the data, you can select Modbus Poll software to read the data. Download and install the Modbus Poll software.
- Open the software, select Setup -> Read/Write Definition. Select the actual device address for Slave ID, 16 Read Input Registers (3x) for Function, and 8 channels for Quantity, Click OK to confirm.
- Select Connection->Connect..., choose the corresponding serial port, set the baud rate to 9600, and select 8 Data bits and None Parity. Click OK to connect.
- After the connection is normal, you can set the analog output current for channels 1-8, with units of uA, ranging from 0-20000uA, i.e., 0-20mA.
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 enter the following command to enter the configuration interface
sudo raspi-config Select Interfacing Options -> Serial Port, select Yes to open the hardware serial port
Then restart 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, make sure to connect A-A, B-B.< br/>
Run the following commands 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
Note: The STM32 demo is based on the NUCLEO-F103RB and RS485 CAN Shield module.
1. Download Demo, find the STM32 project file Modbus.uvprojx in the path Modbus_RTU_Analog_Output_Code\STM32\MDK-ARM, and double-click to open the STM32 project file. Note that you should ensure Keil5 software is installed on your computer before using it.
2. Connect the STM32 to a computer via the STM32 download and debug probe. Compile and download the program to the development board.
3. Install the RS485 CAN Shield module on the STM32. Connect the RS485_A on the RS485 CAN Shield module to the RS485_A on the Modbus RTU Analog Output 8CH via a wire, and connect the RS485_B on the RS485 CAN Shield module to the RS485_B on the Modbus RTU Analog Output 8CH via a wire. Then power on the Modbus RTU Analog Output 8CH and the STM32 sequentially.
4. After the demo runs normally, all channels will output 5mA current.
Arduino
Note: The Arduino demo is based on the UNO PLUS and RS485 CAN Shield module.
1. Download Demo, find the Arduino project file Modbus_RTU_Analog_Output.ino in the path Modbus_RTU_Analog_Output_Code\Arduino\Modbus_RTU_Relay, and double-click to open the Arduino project file. Note that you should ensure Arduino IDE software is installed on your computer before using it.
2. Connect the Arduino to the computer via a USB cable. In the Arduino IDE software, select the Arduino board model under Tools->Board. Choose the COM port that the Arduino is connected to under Tools->Port.
3. After seeing the prompt to connect to the computer in the lower right corner, click to compile and flash the program, and wait for the flashing to complete.
4. Install the RS485 CAN Shield module on the Arduino. Connect the RS485_A on the RS485 CAN Shield module to the RS485_A on the Modbus RTU Analog Output 8CH via a wire, and connect the RS485_B on the RS485 CAN Shield module to the RS485_B on the Modbus RTU Analog Output 8CH via a wire. Then power on the Modbus RTU Analog Output 8CH and the Arduino sequentially.
5. After the demo runs normally, all channels will output 5mA current.
PLC
Note: The PLC demo is based on SIMATIC S7-200 SMART.
1. Download Demo, find the PLC project file modbus_rtu.smart in the path Modbus_RTU_Analog_Output_Code\PLC, and double-click to open the PLC project file. Note that you should ensure STEP 7-MicroWIN SMART software is installed on your computer before using it.
2. Connect the PLC to the computer via a network cable. Click to download
3. Select the communication interface in the communication popup, find your device, and click Confirm
4. In the download pop-up window, check the boxes for program blocks, data blocks, and system blocks, and then click Download.
5. Connect the 485_A on the PLC module to RS485_A on Modbus_RTU_Analog_Output with a wire, and connect the 485_B on the PLC module to RS485_B on Modbus_RTU_Analog_Output with a wire. Then power on the Modbus_RTU_Analog_Output.
6. After powering on the Modbus_RTU_Analog_Output, in the STEP 7-MicroWIN SMART software, find the "PLC" tab in the upper menu bar, switch to this tab, and click the green "RUN" button in the lower "Operation" area to perform the operation to make the PLC enter the running state
7. After the demo runs normally, all channels will output 5mA current.
Development Protocol V2
Function Code Introduction
| Function Code | Description |
|---|---|
| 03 | Read holding register |
| 06 | Write single holding register |
| 10 | Write multiple holding register |
Register Address Introduction
| Address (HEX) | Address storage content | Register value | Permission | Modbus Function Code |
|---|---|---|---|---|
| 4x0000 …… 4x0007 |
Channels 1~8 output data | The values are unsigned hexadecimal | Read/write | 0x03,0x06,0x10 |
| 4x2000 | UART Parameter | The high eight bits indicate the parity mode: 0x00~0x02 The low eight bits indicate the baud rate mode: 0x00~0x07 |
Read/Write | 0x03, 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 |
Operation Command Introduction
Set Single-channel Output Command
Send code: 01 06 00 00 03 E8 89 74
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 06 | 06 Command | Write single register |
| 00 00 | Register Address | 0x0000 - 0x0007 correspond to output data for channels 1~8 |
| 03 E8 | Set Values | Set the value to hexadecimal in uA, with the high bits in front and the low bits in the back 0x03E8 = 1000uA, i.e., 1mA |
| 89 74 | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return code: 01 06 00 00 03 E8 89 74
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 06 | 06 Command | Write single register |
| 00 00 | Register Address | 0x0000 - 0x0007 correspond to data types of 1~8 output channels |
| 03 E8 | Set Values | Set the value to hexadecimal in mV, with the high bits in front and the low bits in the back 0x03E8 = 1000mV, i.e., 1V |
| 89 74 | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Set channel 1 output 1mA : 01 06 00 00 03 E8 89 74 Set channel 2 output 5mA : 01 06 00 01 13 88 D5 5C
Set Multi-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
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 10 | 10 Command | Write multiple registers |
| 00 00 | Register Start Address | 0x0000 - 0x0007 correspond to 1~8 output channels |
| 00 08 | Register Number | Set register number, which must not exceed the maximum number of the channels |
| 10 | Byte Number | Set the number of bytes to be output |
| 03 E8 …… 03 E8 |
Command | Start channel analog output …… Final channel analog output Set the value to hexadecimal in uA, with the high bits in front and the low bits in the back 0x03E8 = 1000uA, i.e., 1mA |
| 3C 05 | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return code: 01 10 00 00 00 08 C1 CF
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 10 | 10 Command | Write multiple registers |
| 00 00 | Register Start Address | 0x0000 - 0x0007 correspond to 1~8 output channels |
| 00 08 | Register Number | Set register number, which must not exceed the maximum number of the channels |
| C1 CF | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Set channels 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 channels 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
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 03 | 03 Command | Read holding register |
| 00 00 | Register Start Address | 0x0000 - 0x0007 correspond to 1~8 input channels |
| 00 08 | Register Number | The number of the registers to be read, which must not exceed the maximum number of the channels |
| 44 0C | CRC16 | The 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
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 03 | 03 Command | Read holding register |
| 10 | Byte Number | The number of all bytes of the returned status information |
| 03 E8 …… 03 E8 |
Output value | Start channel analog output …… Final channel analog output Set the value to hexadecimal in uA, with the high bits in front and the low bits in the back 0x03E8 = 1000uA, i.e., 1mA |
| C1 91 | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Read data types for channels 1-8 : 01 03 00 00 00 08 44 0C Read data type for channel 1 : 01 03 00 00 00 01 84 0A Read data type for channel 2 : 01 03 00 01 00 01 D5 CA Read data type for channels 3-5 : 01 03 00 02 00 03 A4 0B
Set Baudrate Command
Send code: 00 06 20 00 00 05 43 D8
| Field | Description | Note |
|---|---|---|
| 00 | 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 |
| 00 | Parity Method | 0x00: no parity, 0x01: even parity; 0x02: odd parity |
| 05 | Baud Rate Value | Correspondence of baud rate values 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 |
Return code: 00 06 20 00 00 05 43 D8
| Field | Description | Note |
|---|---|---|
| 00 | 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 |
| 00 | Parity Method | 0x00: no parity, 0x01: odd parity; 0x02: even parity |
| 05 | Baud Rate | Correspondence of baud rate values 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 baud rate as 4800: 00 06 20 00 00 00 83 DB Set the baud rate as 9600: 00 06 20 00 00 01 42 1B Set the baud rate as 115200: 00 06 20 00 00 05 43 D8
Set Device Address Command
Send code: 00 06 40 00 00 01 5C 1B
| Field | Description | Note |
|---|---|---|
| 00 | 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 |
| 00 01 | Device Address | Set the device address, 0x0001-0x00FF |
| 5C 1B | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return code: 00 06 40 00 00 01 5C 1B
| Field | Description | Note |
|---|---|---|
| 00 | 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 |
| 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 |
|---|---|---|
| 00 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 03 | 03 Command | Read the device address |
| 40 00 | Command register | 0x4000: read the device address, 0x8000: read software version |
| 00 01 | Byte Number | Fixed 0x0001 |
| 90 1B | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return 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 Number | The number of bytes returned |
| 00 01 | Device Address | Set the device address, 0x0001-0x00FF |
| 79 84 | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 2 device]
Send: 00 03 40 00 00 01 90 1B Return: 02 03 02 00 02 7D 85 // Address 0x02
Read Software Version Command
Send code: 00 03 80 00 00 01 AC 1B
| Field | Description | Note |
|---|---|---|
| 00 | 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 | 0x4000: read the device address, 0x8000: read software version |
| 00 01 | Byte Number | Fixed 0x0001 |
| AC 1B | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return 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 Number | The number of bytes returned |
| 00 64 | Software Version | Converting to decimal and then shifting the decimal point two places to the left will represent the software version
|
| B9 AF | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Send: 00 03 80 00 00 01 AC 1B Return: 01 03 02 00 64 B9 AF //0x0064 = 100 =V1.00
Exception Function Code
When the received command is incorrect or the device is abnormal, an exception response will be returned in the following format:
Return: 01 85 03 02 91
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 85 | Exception Function Code | Exception function code = Request function code + 0x80 |
| 03 | Byte Number | Exception Code |
| 02 91 | CRC16 | The CRC16 checksum of the first 6 bytes of data |
An exception code is a single-byte value that indicates the type of error. Several commonly used exception codes defined by the Modbus protocol:
| Exception Code | Name | Description |
|---|---|---|
| 0x01 | Illegal Function | The requested function code is not supported |
| 0x02 | Illegal Data Address | The requested data address is incorrect |
| 0x03 | Illegal Data Value | The requested data value or operation cannot be executed |
| 0x04 | Server Failure | Server equipment failure |
| 0x05 | Response | The request has been received and is being processed |
| 0x06 | Device Busy | The device is currently busy and cannot perform the requested operation |
Resources
Demos
Software
Related Resources
FAQ
The device does not require an additional driver download. You can control the device relay's on/off or query the relay status by sending Modbus commands through the device's 485 interface.
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There is no DIP switch, it can only be set through commands
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Please refer to Modbus Series BootLoader Description to eEnter the boot mode, then you can select option 3 to read communication parameters or select option 2 to reset communication parameters
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Check if the 485 bus is reversed. If not, connect a 120 Ω terminal resistor across the A and B cables
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Under 5V power supply, the reference power consumption when in standby mode: 0.39W. Please refer to actual conditions for specific power consumption
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The device is in linkage mode at this time, just switch to other modes
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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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