LM LoRa DTU
RS232 / RS485 to LoRa wireless data transfer unit
LM LoRa DTU transmits data using LoRa modulation, so equipment with RS232 or RS485 serial ports can communicate over a long-range wireless link. Control it directly with AT commands, or configure it as a master or slave that exchanges data with field devices over Modbus.
- Interface
- RS232 / RS485
- Power
- 12–36 VDC
- Operating temp
- -40 to 85 °C
- NCC approval
- CCAJ23LP2990T7
Features
-
Point-to-point and addressed sending
Point-to-point communication, with the option to send data to a specific node.
-
Master–slave mode
Configure as master or slave to exchange data with field devices over Modbus.
-
Encrypted transmission
Supports encrypted data transmission to protect field data.
-
AT command configuration
Set parameters with AT commands, with a PC configuration tool for testing.
-
Industrial protection
ESD level 4, level 3 surge protection on power and RS232/RS485, and a hardware watchdog.
-
Wide-range power input
12–36 VDC input that works with either polarity, with TVS protection.
Specifications
Radio parameters vary by frequency version. Units sold in Taiwan are the NCC-approved 920–925 MHz version.
| Radio | |
|---|---|
| Frequency band | 920–925 MHz (NCC-approved Taiwan version); other frequency versions available on request |
| Transmit power | Up to 22 dBm (Taiwan version set to NCC limits) |
| Receive sensitivity | Down to -148 dBm (SF12, 10.4 kHz bandwidth) |
| Range | About 4,000 m (open line of sight, 22 dBm, 2 dBi antenna, 2 m height, SF12) |
| Antenna connector | SMA (external thread, inner hole), 50 Ω |
| Interface | |
| Data interface | RS232 (DB9 female), RS485 (3.81 mm terminal) |
| Baud rate | 1200–115200 bps, default 9600 bps |
| Max. packet length | 240 bytes |
| Indicators | 5 LEDs: POWER, LoRa TX, LoRa RX, DTU TX, DTU RX |
| Buttons | Reset (RST), factory reset (RTD, hold 10 seconds) |
| Power | |
| Input voltage | 12–36 VDC with TVS protection |
| Power connector | DC 5.5 × 2.1 mm jack or 3.81 mm terminal |
| Current | TX peak 40 mA, standby 3 mA (12 V input) |
| Environment | |
| Operating temperature | -40 to 85 °C |
| Storage temperature | -45 to 125 °C |
| Humidity | Operating 5–95 %RH, storage 1–95 %RH (non-condensing) |
| Protection | |
| ESD | Level 4 |
| Surge | Level 3 on power and RS232/RS485 |
| System | Hardware watchdog |
Operating modes
General transparent mode
The host controller drives every action with AT commands, such as entering receive mode or sending data: one command, one action.
Master–slave transparent mode
The DTU enters receive mode at power-up. The master sends data from its serial port to slaves over LoRa; each slave passes it to the field device and returns the reply to the master, which suits Modbus polling.
- Same-frequency
- Uplink and downlink use the same frequency.
- Different-frequency
- Uplink and downlink use separate frequencies, for example 920 MHz from the master and 920.5 MHz back from the slave.
Applications
Wireless Modbus over LoRa
A server connects to the LoRa master over RS232 or RS485 and sends Modbus commands. Each slave DTU’s RS485 bus can chain sensors, meters, remote IO or industrial panels; the device whose address matches executes the command and returns the result.
Gateway with a 4G DTU
At outdoor sites without wired networks, a 4G DTU connected to the LoRa master sends data from LoRa slaves to an MQTT server over the cellular network.
Certification
This product has type approval for telecommunications-controlled radio frequency devices from Taiwan’s National Communications Commission (NCC).
- Approval label
- CCAJ23LP2990T7
- Model
- LM_DTU
- Device
- RS485/RS232 to LoRa data transfer unit
- Frequency
- 920–925 MHz
- Approval date
- July 31, 2023
Planning to use LM LoRa DTU in a project?
Tell us your application, quantity and timeline, and we will send a quote and recommend the right frequency version.