R4DCB08 Temperature Collector Python Interface

A Python library and command-line interface for communicating with R4DCB08 8-channel temperature collectors using Modbus RTU (serial) and TCP protocols.

You can check my blog to more usage examples: https://hackthechaos.com/blog/ds18b20-rs485-raspberry-pi/

Features

• Read temperatures from all 8 channels
• Read temperature from individual channels
• Set temperature correction values for calibration
• Read current temperature corrections
• Support for both Modbus RTU (serial) and TCP connections
• Command-line interface for easy automation
• Simple Python API for integration

R4DCB08 Technical Specifications

Feature	Details
Operating Voltage	6-24V DC
Operating Current	8-13mA (depends on connected DS18B20 sensors)
Temperature Range	-55°C to +125°C
Accuracy	±0.5°C from -10°C to +85°C
Baud Rates	1200, 2400, 4800, 9600 (default), 19200
Data Format	N, 8, 1 (No parity, 8 data bits, 1 stop bit)
Communication Protocol	Modbus RTU
Temperature Channels	8 channels (DS18B20 sensors)
Default Address	1

Installation

1. Create a Python virtual environment:

python -m venv .venv
source .venv/bin/activate  # Linux/macOS
# or
.venv\Scripts\activate     # Windows

2. Install dependencies:

pip install -r requirement.txt

Required Packages

pyserial
pymodbus

Usage

Command Line Interface

The r4dcb08_cli.py script provides a complete command-line interface supporting both Modbus RTU (serial) and TCP connections:

Basic Usage

python r4dcb08_cli.py {rtu|tcp} [OPTIONS] COMMAND

Connection Types

RTU (Serial) Connection

python r4dcb08_cli.py rtu --port /dev/ttyUSB0 [OPTIONS] COMMAND

RTU Connection Options:

• --port, -p: Serial port (required, e.g., /dev/ttyUSB0, COM3)
• --address, -a: Modbus device address (1-247, default: 1)
• --baudrate, -b: Baud rate (1200, 2400, 4800, 9600, 19200, default: 9600)
• --timeout, -t: Communication timeout in seconds (default: 1.0)

TCP Connection

python r4dcb08_cli.py tcp --host 192.168.1.100 [OPTIONS] COMMAND

TCP Connection Options:

• --host, -H: TCP host IP address (required, e.g., 192.168.1.100)
• --port, -p: TCP port (default: 502)
• --address, -a: Modbus device address (1-247, default: 1)
• --timeout, -t: Communication timeout in seconds (default: 1.0)

Available Commands

1. Read All Temperatures

Read temperatures from all 8 channels:

RTU:

python r4dcb08_cli.py rtu --port /dev/ttyUSB0 --address 1 read-all

TCP:

python r4dcb08_cli.py tcp --host 192.168.1.100 read-all

Output:

R4DCB08 Temperature Readings:
-----------------------------------
Channel 0: 22.5°C
Channel 1: 23.1°C
Channel 2: No sensor
Channel 3: 21.8°C
...

2. Read Single Channel Temperature

Read temperature from a specific channel (0-7):

RTU:

python r4dcb08_cli.py rtu --port /dev/ttyUSB0 read-channel 0

TCP:

python r4dcb08_cli.py tcp --host 192.168.1.100 read-channel 3

Output:

Channel 0: 22.5°C

3. Set Temperature Correction

Set a temperature correction value for calibration:

RTU:

python r4dcb08_cli.py rtu --port /dev/ttyUSB0 set-correction 3 1.5

TCP:

python r4dcb08_cli.py tcp --host 192.168.1.100 set-correction 0 2.1

This adds a correction to the specified channel. Corrections can be negative:

python r4dcb08_cli.py rtu --port /dev/ttyUSB0 set-correction 2 -0.8

4. Read Temperature Corrections

View current correction values for all channels:

RTU:

python r4dcb08_cli.py rtu --port /dev/ttyUSB0 read-corrections

TCP:

python r4dcb08_cli.py tcp --host 192.168.1.100 read-corrections

Output:

Temperature Correction Values:
-----------------------------------
Channel 0: +0.0°C
Channel 1: +1.2°C
Channel 2: -0.8°C
Channel 3: +1.5°C
...

Example Commands

# RTU (Serial) examples - Linux/macOS
python r4dcb08_cli.py rtu --port /dev/ttyUSB0 --address 1 read-all
python r4dcb08_cli.py rtu --port /dev/ttyUSB0 read-channel 5
python r4dcb08_cli.py rtu --port /dev/ttyUSB0 set-correction 0 2.1

# RTU (Serial) examples - Windows  
python r4dcb08_cli.py rtu --port COM3 --address 2 read-all
python r4dcb08_cli.py rtu --port COM3 --baudrate 19200 read-channel 3

# RTU with different device address and baud rate
python r4dcb08_cli.py rtu --port /dev/ttyUSB0 --address 5 --baudrate 19200 read-all

# TCP examples
python r4dcb08_cli.py tcp --host 192.168.1.100 read-all
python r4dcb08_cli.py tcp --host 192.168.1.100 --port 502 read-channel 2
python r4dcb08_cli.py tcp --host 192.168.1.100 --address 3 set-correction 1 1.5

# TCP with custom port and longer timeout
python r4dcb08_cli.py tcp --host 192.168.31.223 --port 4196 --timeout 5.0 read-all
python r4dcb08_cli.py tcp --host 192.168.31.223 --port 4196 --timeout 5.0 read-channel 0

Python API Usage

You can also use the R4DCB08Client class directly in your Python code:

RTU (Serial) Example

from r4dcb08_cli import R4DCB08Client

# Create RTU client
client = R4DCB08Client(address=1, serial_port="/dev/ttyUSB0", baudrate=9600)

# Connect
if client.connect():
    try:
        # Read all temperatures
        temperatures = client.read_all_temperatures()
        for i, temp in enumerate(temperatures):
            if temp is not None:
                print(f"Channel {i}: {temp:.1f}°C")
        
        # Read single channel
        temp = client.read_single_temperature(0)
        print(f"Channel 0: {temp:.1f}°C")
        
        # Set correction
        client.set_temperature_correction(0, 1.5)
        
    finally:
        client.disconnect()

TCP Example

from r4dcb08_cli import R4DCB08Client

# Create TCP client
client = R4DCB08Client(address=1, host="192.168.1.100", tcp_port=502)

# Connect
if client.connect():
    try:
        # Read all temperatures
        temperatures = client.read_all_temperatures()
        for i, temp in enumerate(temperatures):
            if temp is not None:
                print(f"Channel {i}: {temp:.1f}°C")
        
        # Set correction for channel 2
        client.set_temperature_correction(2, -0.5)
        
    finally:
        client.disconnect()

Protocol Information

Register Map

• 0x0000-0x0007: Temperature readings (8 registers, one per channel)
• 0x0008-0x000F: Temperature corrections (8 registers, one per channel)

Temperature Encoding

• Temperature values are stored as signed 16-bit integers
• Actual temperature = raw_value / 10.0
• Example: 235 = 23.5°C, -150 = -15.0°C
• 0x8000 (32768) = sensor error/disconnected

Connection Settings

# Correct settings for R4DCB08
baudrate = 9600    # Default, can be 1200, 2400, 4800, 9600, 19200
parity = 'N'       # No parity (important!)
stopbits = 1       # 1 stop bit
bytesize = 8       # 8 data bits

Troubleshooting

Connection Issues

1. Device not responding:

   • Ensure R4DCB08 is powered (6-24V DC)
   • Check serial cable connection
   • Verify correct serial port path

2. Communication errors:

   • Confirm device address (default: 1)
   • Check baud rate setting (default: 9600)
   • Ensure no other program is using the serial port
   • Verify parity is set to 'N' (None)

3. TCP connection issues:

   • Verify the host IP address is correct and reachable
   • Check that the TCP port is correct (default: 502, custom: 4196, etc.)
   • Some TCP connections may require longer timeout (use --timeout 5.0)
   • Ensure firewall allows the connection

Temperature Reading Issues

1. "No sensor" readings:

   • Check DS18B20 sensor connections
   • Verify if sensors is powered by checking voltage between 5V and ground, also D* line should have about 5 V to ground
   • Test sensors individually or replace with known working sensors

2. Incorrect temperature values:

   • Check temperature corrections with read-corrections
   • Verify sensor calibration
   • Check for electromagnetic interference

Common Error Messages

• "Failed to connect": Check port path and permissions
• "Modbus error": Device communication issue, check address/baud rate
• "Channel must be 0-7": Invalid channel number specified
• "Correction must be between -327.6 and +327.6": Correction value out of range

Hardware Setup

1. Connect R4DCB08 to power supply (6-24V DC)
2. Connect DS18B20 temperature sensors to the 8 channels
3. Connect USB-to-RS485 converter to your computer
4. Connect RS485 A/B lines to R4DCB08 Modbus terminals

License

This project is licensed under the MIT License - see the LICENSE file for details.