Modbus RTU Analog Input 8CH
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Overview
Hardware Description
- Each channel can be individually configured for its range, making it more convenient for users.
"AIN+" is the positive input, and "AIN-" is the negative input. The module supports both differential and single-ended input. When used as a single-ended input, "AIN-" is connected to the ground.
Note: When inputting the different powers, it is important to connect the ground wire to establish a common ground. Otherwise, the collected data may be inaccurate.
- Opening the device case, you can see jumpers are near the device terminals, corresponding to the eight channels AI1~AI8. You need to select the jumper mode based on the measurement signal; otherwise, the measurement data will be inaccurate.
- When measuring voltage signals, the jumper wire for the corresponding channel should be disconnected.
- When measuring current signals, the jumper wire for the corresponding channel should be connected.
- Modbus RTU Analog Input 8CH defaults to current mode with the jumper wire connected. Modbus RTU Analog Input 8CH (B) defaults to voltage mode with the jumper wire disconnected.
Version Comparision
- Currently, there are two versions of the analog input series, one defaults to current input, and the other defaults to voltage input.
| Version | Modbus RTU Analog Input 8CH | Modbus RTU Analog Input 8CH (B) |
|---|---|---|
| Default mode | 8-ch current mode, 0~20mA | 8-ch voltage mode, 0~10V |
| Measurement range | 0~5V/1~5V 0~20mA/4~20mA |
0~10V/2~10V 0~20mA/4~20mA |
| Resolution | 12-bit | 12-bit |
| Current sampling resistance | 249Ω | 499Ω |
| Operational amplifier ratio | 32.4/49.9 | 10/32.4 |
| Channel | 8-AI | 8-AI |
- Each version has five range modes from 0 to 4.
| Mode | Modbus RTU Analog Input 8CH | Modbus RTU Analog Input 8CH (B) |
|---|---|---|
| 0 | 0~5V voltage mode | 0~10V voltage mode |
| 1 | 1~5V voltage mode | 2~10V voltage mode |
| 2 | 0~20mA current mode | 0~20mA current mode |
| 3 | 4~20mA current mode | 4~20mA current mode |
| 4 | 4096-scale code mode | 4096-scale code mode |
- The scale code is the data collected by the AD converter and needs to undergo a linear transformation to obtain voltage or current data. The conversion formula is as follows.
- Voltage = Scale Code * 3300/4095/Operational Amplifier Ratio
- Current = Voltage/Sampling Resistor
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 it will return the 8-channel analog input data normally.
01 04 00 00 00 08 F1 CC
- 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 4-20mA current input mode.
01 06 10 00 00 03
- 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, 04 Read Input Registers (3x) for Function, and 8 channels for Quantity, and 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 successful connection, it can display the analog input data for channels 1-8.
- Modbus RTU Analog Input 8CH (A) displays the current by default, and the unit is uA. Modbus RTU Analog Input 8CH (B) displays the voltage by default, and the unit is mV.
- Choose File->New to create a new window, select Setup->Read/Write Definition. Select the actual device address for Slave ID, 16 Write Multiple Registers for Function, Hex for Address Mode, 1000 for Address, and 8 channels for Quantity, and then click "OK" to confirm.
- The new window 2 can set up the measuring modes for different channels. For example, you can set the channel 1 mode as 2, that is, 0~20mA current mode. And channel 1 of the window 1 will display the current.
Note: The internal jumper wires should be modified when changing the current and voltage mode, otherwise, the measurement data will not be accurate.
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, disable shell access, and enable the hardware serial port
Then restart Raspberry Pi:
sudo reboot
Open the /boot/config.txt file, find the following configuration statement to enable the serial port, if not, you can add it to the end of the file.
enable_uart=1
For Raspberry Pi 3B users, the serial port is used for Bluetooth and needs to be commented out:
#dtoverlay=pi3-miniuart-bt
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.
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-Input-8CH/Modbus_RTU_Analog_Input_Code.zip unzip Modbus_RTU_Analog_Input_Code.zip cd Modbus_RTU_Analog_Input_Code/Python3 sudo python3 modbus.py
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_Input_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 Input 8CH via a wire, and connect the RS485_B on the RS485 CAN Shield module to the RS485_B on the Modbus RTU Analog Input 8CH via a wire. Then power on the Modbus RTU Analog Input 8CH and the STM32 sequentially.
4. After the program runs normally, you can observe through the serial port assistant that the device prints the collected results
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_Input.ino in the path Modbus_RTU_Analog_Input_Code\Arduino\Modbus_RTU_Analog_Input, 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 Input 8CH via a wire, and connect the RS485_B on the RS485 CAN Shield module to the RS485_B on the Modbus RTU Analog Input 8CH via a wire. Then power on the Modbus RTU Analog Input 8CH and the Arduino sequentially.
5. After the program runs normally, you can observe through the serial port assistant that the device prints the collected results
Development Protocol V2
Function Code Introduction
| Function Code | Description |
|---|---|
| 03 | Read holding register |
| 04 | Read input 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 |
|---|---|---|---|---|
| 3x0000 …… 3x0007 |
Channels 1~8 input data | Read values as unsigned hexadecimal | Read | 0x04 |
| 4x1000 …… 4x1007 |
Channels 1~8 data types | 0x0000~0x0004 five ranges | 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
Read Analog Input Command
Send code: 01 04 00 00 00 08 F1 CC
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 04 | 04 command | Read input 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 |
| F1 CC | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return code: 01 04 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 2C
| Field | Description | Note |
|---|---|---|
| 01 | Device Address | 0x00 indicates the broadcast address, 0x01-0xFF indicates the device address |
| 04 | 04 command | Read input register |
| 10 | Byte Number | Data length |
| 00 00 …… 00 00 |
Register data | Indicates the values of analog inputs from channels 0 - 7 An unsigned 16-bit identifier for a channel, with the higher bits first and the lower bits last The data range is determined by the output data type |
| 55 2C | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Read 1-8 channels : 01 04 00 00 00 08 F1 CC Read 1 channel : 01 04 00 00 00 01 31 CA Read 2 channel : 01 04 00 01 00 01 60 0A Read 3-5 channels : 01 04 00 02 00 03 11 CB
Read Channel Data Type Command
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 Command | Read holding register |
| 10 00 | Register Start Address | 0x1000 - 0x1007 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 |
| 40 CC | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return code: 01 03 10 00 02 00 02 00 02 00 02 00 02 00 02 00 02 00 02 09 C3
| 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 |
| 00 02 …… 00 02 |
Data Type | Indicates data types of 0-7 channels, 0x0000~0x0004 represents five ranges 0x0000: Range 0~5V, output range 0~5000 or 0~10000, unit mV; 0x0001: Range 1~5V, output range 1000~5000 or 2~10V, output range 2000~10000, unit mV; 0x0002: Range 0~20mA, output range 0~20000, unit uA; 0x0003: Range 4~20mA, output range 4000~20000, unit uA; 0x0004: Direct output of numerical code, output range 0~4096, requires linear conversion to obtain actual measured voltage and current; |
| 09 C3 | 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 10 00 00 08 40 CC Read data type for channel 1 : 01 03 10 00 00 01 80 CA Read data type for channel 2 : 01 03 10 01 00 01 D1 0A Read data type for channels 3-5 : 01 03 10 02 00 03 A0 CB
Set Single-channel Data Type Command
Send code: 01 06 10 00 00 03 CD 0B
| 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 correspond to data types of 1~8 input channels |
| 00 03 | Channel Data Type | Channel data types, 0x0000~0x0004 represents five ranges 0x0000: Range 0~5V, output range 0~5000 or 0~10000, unit mV; 0x0001: Range 1~5V, output range 1000~5000 or 2~10V, output range 2000~10000, unit mV; 0x0002: Range 0~20mA, output range 0~20000, unit uA; 0x0003: Range 4~20mA, output range 4000~20000, unit uA; 0x0004: Direct output of numerical code, output range 0~4096, requires linear conversion to obtain actual measured voltage and current; |
| CD 0B | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return code: 01 06 10 00 00 03 CD 0B
| 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 | Channel Data Type Address | 0x1000 - 0x1007 correspond to data types of 1~8 input channels |
| 00 03 | Channel Data Type | Channel data type, 0x0000~0x0004 represents five ranges |
| CD 0B | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Set data type to 0~20mA for channel 1 : 01 06 10 00 00 02 0C CB Read data type 4~20mA for channel 2: 01 06 10 01 00 03 9C CB
Set Multi-channel Data Type Command
Send code: 01 10 10 00 00 08 10 00 03 00 03 00 03 00 03 00 03 00 03 00 03 00 03 91 2B
| 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 correspond to data types of 1~8 input 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 |
| 00 03 …… 00 03 |
Command | Corresponding to data types of 0-7 channels, 0x0000~0x0004 represents five ranges 0x0000: Range 0~5V, output range 0~5000 or 0~10000, unit mV; 0x0001: Range 1~5V, output range 1000~5000 or 2~10V, output range 2000~10000, unit mV; 0x0002: Range 0~20mA, output range 0~20000, unit uA; 0x0003: Range 4~20mA, output range 4000~20000, unit uA; 0x0004: Direct output of numerical code, output range 0~4096, requires linear conversion to obtain actual measured voltage and current; |
| 91 2B | CRC16 | The CRC16 checksum of the first 6 bytes of data |
Return 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 correspond to data types of 1~8 input channels |
| 00 08 | Register Number | Set register number, which must not exceed the maximum number of the channels |
| C5 0F | CRC16 | The CRC16 checksum of the first 6 bytes of data |
For example: [Address 1 device]
Read data type 4~20mA for channels 1-8: 01 10 10 00 00 08 10 00 03 00 03 00 03 00 03 00 03 00 03 00 03 00 03 91 2B Read data type 1~5V for channels 3-5 : 01 10 10 02 00 03 06 00 01 00 01 00 01 BE 4A
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 0x0064 = 100 = V1.00 |
| B9 AF | CRC16 | The 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
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
Demo
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 enter 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: 0.395W. Please refer to actual conditions for specific power consumption
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For the Modbus RTU Analog Input 8CH module, it is recommended that the maximum input value does not exceed 5V 20mA, and actual operation should be within this range.
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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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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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