tMDS-16 is a temperature measurement module designed for Modbus RTU-based systems. It features two independent 1-Wire buses, each capable of connecting up to 8 DS18B20 temperature sensors, allowing for a total of 16 sensors.
Temperature data is made available via Modbus registers, which include both the current sensor readings and corresponding offset values used for calibration. This ensures accurate and consistent measurements across all connected sensors.
The tMDS-16 is primarily designed to function as an extension module for LK4 or LK3.5+ devices (also compatible with LK3.9), enabling scalable and distributed temperature monitoring.
A ready-to-use configuration file for these devices is available, allowing for quick and hassle-free integration.
By default, the device uses Modbus Slave ID 1, which can be changed via the USB serial console.
The tMDS-16 integrates seamlessly with LK4 and LK3.5+ devices. It can be powered directly from the LK controller using its 5V and GND outputs. Then, connect it—either alone or together with other Modbus devices—to the LK’s Modbus A+ and B− terminals to establish communication.
Once connected, configure a custom Modbus module on the LK using the ready-to-use configuration preset available in the Downloads section. You can easily modify this preset to read only the parameters you need, such as selected temperature sensors or calibration offsets.
To update the firmware, the tMDS-16 must be placed into bootloader mode. In this mode, the device appears as a mass storage device named RPI-RP2 when connected to a PC. Simply copy the new firmware file to that storage. After the upload, the device will automatically restart and resume normal operation with the new firmware.
You can enable bootloader mode in one of two ways:
Via USB Console
Connect the device to a PC and open the serial console (see instructions in Advanced configuration).
Then, send the command: bootloader.
The connection will be interrupted, and the device will restart in bootloader mode.
Via Hardware Button
Open the device casing to access the FLASH / SW1 button.
Press and hold this button before connecting the device to the PC via USB.
Keep holding it for a moment as the device powers on. Once it enters bootloader mode, you can release the button.
💡 Firmware files are available in the Downloads section.
The function button on the tMDS-16 offers a simple and intuitive way to perform essential setup actions – no USB connection required. This makes it ideal for quick configuration in the field.
The button is located next to the 1-Wire bus connectors, with a status LED positioned between them. The LED provides feedback indicating which function is about to be executed, depending on how long the button is held.
To modify the settings, you will need to connect the tMDS-16 to a computer via USB. The device can be powered through USB, so no additional power connections are necessary.
To establish a connection with the pulse counter, you'll need an application that can handle serial communication. Popular choices include:
PuTTy
TeraTerm
PySerial (Python library), which includes useful tools like pyserial-miniterm (for managing connections) and pyserial-ports (for listing available COM ports).
List Available Ports:
Run pyserial-ports to list the available COM ports before connecting the device. The output might look like:
COM1
COM3
COM15
COM16
COM17
Connect the Device
Plug in the tMDS-16 and run the command again. The new COM port (e.g., COM11) will represent the connected device.
Connect to tMDS-16
Use the following connection parameters:
Baud rate: 115200
Byte size: 8 bits
Parity: None
Stop bits: 1
Example command:
pyserial-miniterm COM11 115200
Send Commands
Once connected, you can issue commands to the device. Each command must be followed by the Enter key. A useful command is ? or help, which provides a list of all available commands (described below).
Reboot the device into bootloader mode to update the firmware. When connected to a computer, it will appear as a storage device named RPI-RP2, to which you should copy the firmware file with the extension uf2. Then the device will reboot into normal operation mode.
restart
Restart the device.
verbose=X | v=X
Turn on or off verbose mode, which displays more messages.
help | ?
Display this help message with a list of available commands.
Below are practical examples of how to configure and use the tMDS-16 via the console. These scenarios cover the most common integration and calibration tasks.
🔧 1. Changing the Modbus Slave address
When using multiple Modbus devices on the same bus, assign a unique address to each.
address=5
Then save the new setting:
save_config
🌡️ 2. Calibrating sensor readings manually
If you want to fine-tune readings from individual sensors, use per-sensor offsets.
Example: Set an offset of −0.5°C for sensor 3:
offset3=-0.5
Save the changes:
save_config
⚙️ 3. Auto-calibrating all sensors
To align readings across all connected DS18B20 sensors, use the following command:
set_offsets
This command calculates the average temperature across all active sensors and applies an offset to each one so that their readings match this average. It helps eliminate small factory variances and improves consistency when the sensors are later placed in different environments.
🛈 Before running this command, it is recommended to place all sensors in the same location with a stable temperature, wait a short while for them to equalize, and then execute the calibration.
This command automatically saves the calculated offsets to Flash memory.
🔍 4. Reading current sensor values
To display temperature readings directly in the console:
read_sensors
♻️ 5. Detecting connected sensors
After connecting new sensors or replacing old ones, update the device’s sensor list:
update_sensors
To reset all sensor IDs and their offsets:
reset_sensors
🧪 6. Inspecting Modbus registers
To check live register values exposed by the device:
Below is the list of Modbus registers available in the device.
The content corresponds to the output of the read_definitions command and includes register names, addresses, types, and divisors.
Tinycontrol
