SX1262-LoRa-DTU-xF
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Overview
- This product does not support LoRaWAN.
- This product only supports SX1262-LoRa-DTU-xF and USB-TO-LoRa-xF communication.
- At least 2x SX1262-LoRa-DTU-HF are required to form a LoRa communication network (SX1262-LoRa-DTU-LF is the same).
Introduction
SX1262-LoRa-DTU is a wireless data transfer unit with RS232, RS485, and RS422 interfaces based on the SX1262 module. Adopts LoRa Modulate and Demodulate technology, with the advantages of anti-interference and long-distance communication (up to 5KM). Supports point-to-point, point-to-multipoint, relay network, AES, etc. As it is compact and easy to install, SX1262-LoRa-DTU-xF is suitable for wireless data transmission and device control of industry standard or non-standard user protocol.
Feature
- Adopts LoRa Modulate and Demodulate technology, anti-interference, and long-distance communication.
- Adopts the original SX1262 chip, with -148dBm reception sensitivity and 22dBm emit power.
- Supports preamble detection, with CRC, automatic packetization, 960 bytes cache functions.
- Supports LBT sending, RSSI output, and AT command configuration.
- AES communication to ensure data transmission security.
- Supports multi-level relay networking to increase the wireless communication distance.
- Supports host configuration and firmware upgrade (support firmware customization for batch order).
- Adopts high-quality components such as TCXO to ensure stable operation under harsh working conditions.
- Comes with online development resources and manuals.
Parameters
| Communication Interface | |
| Interface | Screw terminals: RS485 × 1, RS422 × 1 DB9 male connector: RS232 × 1 SMA-KE female connector: 6dBi omni-directional antenna × 1 |
| RS485 | Anti-surge, overcurrent protection (reserved 120R balanced resistor header) |
| RS232 | TVS diode, anti-surge, and ESD protection |
| RS422 | Anti-surge, overcurrent protection (reserved 120R balanced resistor header) |
| Wireless Parameters | |
| Frequency Band | Sub-GHz (410~510MHz, 850~930MHz) |
| Signal Modulation | LoRa |
| Encryption | AES |
| Emit Power | +22dBm Max |
| Reception Sensitivity | -148dBm |
| UART Parameters | |
| Baud Rate | 1200 ~ 115200bps |
| Parity Bit | None |
| Data bit | 8 ~ 9 bits |
| Flow Control | N/F |
| Environmental Requirements | |
| Operating Temperature | 0 ~ 85℃ |
| Humidity Range | 5% ~ 95% relative humidity |
| Others | |
| Power Supply | Screw terminals 6 ~ 28V or DC 12V, overcurrent, overvoltage and reverse-proof |
| Case | Aluminum alloy |
| Dimensions | 77.0 × 24.0 × 64.2mm |
Hardware Description
- This product does not support LoRaWAN.
- This product only supports SX1262-LoRa-DTU-xF and USB-TO-LoRa-xF communication.
- At least 2x SX1262-LoRa-DTU-HF are required to form a LoRa communication network (SX1262-LoRa-DTU-LF is the same).
- When installing the SX1262-LoRa-DTU-xF (hereinafter referred to as DTU), position the SMA antenna interface upwards and the LED light facing outward. The back has a 35mm DIN latch embedded for fixing with a latch. Install the antenna, RS485, RS232, or RS422 interface cables in sequence, and finally, connect the DC12V power supply or terminal for power (only one power source needs to be connected).
- Note: it is not possible to simultaneously convert RS232, RS485, and RS422 to LoRa, and the RS232, RS485, and RS422 interfaces for the same LoRa module cannot be converted to one another.
Interface Description
RS485
- TA, and TB at the bottom of DTU are RS485 half-duplex bus interfaces. (Starting from V1.2 firmware, RS485 is the default interface. The baud rate is 9600, and the mode is 8N1.)
- Note that if the RS485 interface is blocked and the DTU receives the LoRa message, the RS485 interface has switched to output mode and does not receive data any more.
RS232
- The DB9 male plug on the top of DTU is the RS232 full-duplex bus interface.
RS422
- DTU bottom TA, TB, RA, and RB are RS422 full-duplex bus interfaces.
- Note: RS485 bus interface multiplexes the sending end of RS422.
SMA Port (Antenna)
- The SMA interface on the top of the DTU is a supporting 6dBi omnidirectional antenna interface.
Power Port
- DC12V power supply: Use the matching AC-DC power supply to connect the DTU.
- Terminal 6~28V power supply: 6-28V at the 6-pin green terminal, GND is the DC power supply port.
Indicator
- PWR: When connected to DC12V or terminal power supply, the PWR indicator is always on.
- TXD: When sending data, the TXD indicator is on, and it goes out after sending.
- RXD: When receiving data, the RXD indicator is on, and it goes out after receiving.
Key
- KEY: Note: Do not press the button within 3 seconds after powering on.
- Press and hold the KEY within 3 seconds of powering on or before powering on. After holding the key for two seconds, release the KEY when TXD and RXD flash, indicating entry into firmware update mode (starting from firmware version 1.1).
- After powering on for 3 seconds, the TXD and RXD indicators blink at the same time to enter the default operating status.
- After 3 seconds of powering on, lightly touch the KEY at 1-second intervals and then release the button to switch between RS485, RS232, and RS422 COMx modes.
- After 3 seconds of powering on, hold down the KEY button until the RXD light is off, then release the KEY button. This will restore factory parameter settings and automatically reboot.
Dimensions
LoRa & LoRaWAN
What is LoRa ?
[Semtech]'s LoRa is a long-distance, low-power wireless platform for the Internet of Things (IoT), which generally refers to radio frequency chips using LoRa technology. The main features are as follows:
- The spread spectrum modulation technology adopted by LoRa (abbreviation of long-range) is derived from Chirp Spread Spectrum (CSS) technology, which is one of the long-distance wireless transmission technology and LPWAN communication technology. Spread spectrum technology uses bandwidth for sensitivity technology, Wi-Fi, ZigBee, etc. all use spread spectrum technology, but the characteristic of LoRa modulation is that it is close to the limit of Shannon's theorem, and the sensitivity can be improved with maximum efficiency. Compared with traditional FSK technology, at the same communication rate, LoRa is more sensitive than FSK by 8 ~12dBm. At present, LoRa mainly operates in the ISM frequency band of Sub-GHz.
- LoRa technology integrates technologies such as digital spread spectrum, digital signal processing, and forward error correction coding, which greatly improves the performance of long-distance communication. Lora's link budget is better than any other standardized communication technology. The link budget refers to the main factors that determine the distance in a given environment.
- LoRa RF chips mainly include SX127X series, SX126X series and SX130X series, of which SX127X and SX126X series are used for LoRa nodes, and SX130X is used for LoRa gateways. For details, please refer to [Semtech]'s product list.
What is LoRaWAN ?
- LoWAN is an open protocol for low-power wide-area networks based on LoRa radio modulation technology. Designed to wirelessly connect battery-powered "things" to the Internet in regional, national or global networks, and target critical Internet of Things (IoT) requirements such as two-way directional communication, end-to-end security, mobility, and localized services. The node wirelessly connects to the Internet with network access authentication, which is equivalent to establishing an encrypted communication channel between the node and the server. The LoRaWAN protocol level is shown in the figure below.
- The Class A/B/C node devices in the MAC layer basically cover all the application scenarios of the Internet of Things. The differences among the three nodes lie in the different time slots of sending and receiving for nodes.
- EU868 and AS430 in the Modulation layer show that frequency band parameters are different in different countries. Please click the reference [link] for regional parameters.
- To achieve LoRaWAN network coverage in cities or other areas, it needs to be composed of four parts: nodes (LoRa node RF chips), gateways (or base stations, LoRa gateway RF chips), Servers and clouds, as shown in the figure below:
- DEVICE (node device) needs to initiate a network access request packet to GATEWAY (gateway) and then to the server. After passing the authentication, it can normally send and receive application data from the server.
- GATEWAY (gateway) can communicate with the server via a wired network or 3/4/5G wireless network.
- The main operators on the server side include TTN, etc. For building cloud services by yourself, please refer to lorawan-stack, chirpstack.
Application
LoRa devices and networks such as LoRaWAN enable smart IoT applications to help solve the planet's formidable challenges in energy management, natural resource reduction, pollution control, infrastructure efficiency, disaster prevention, and more. Semtech's LoRa devices have achieved hundreds of successful use cases in smart cities, homes and buildings, communities, metrology, supply chain, logistics, agriculture, and more. LoRa networks have covered hundreds of millions of devices in more than 100 countries and are committed to a smarter planet.
How To Use
Boot Test
- This test uses two sets of USB to RS232 cables and DTUs connected to PC Windows 10, DTU uses an RS232 interface for streaming mode transmission by default when powered on.
- Install DTU's antenna, RS485/RS232/RS422 interface circuit according to the #Hardware Description chapter (power on with RS485 by default, switch to other interfaces to refer to the AT command set), power supply, etc.
- Download and open the AT setting tool or other serial port assistant tools, connect the USB to the RS232 serial port number, set the baud rate to 9600, and finally click to open the serial port.
- After entering the data in the SSCOM sending area, click the send button, the received data will be printed on the other set of DTU, and vice versa, as shown in the figure below.
- Similarly, other acquisition devices such as PLC can also use DTU to send and receive data.
AT Commands
- The DTU works in the stream transmission mode of the RS232 interface by default, and the default parameters can be used for pairing and sending. The default parameters are as follows:
| Item | Parameter Default Value |
| Spreading Factor | Default 7, (7~12 optional) |
| Bandwidth | Default 0: 125KHz (1:250, 2:500 (KHz) optional) |
| Code Rate | Default 1:4/5 (2:4/6, 3:4/7, 4:4/8 optional) |
| Emit Power | Default 22dBm (10~22dBm optional) |
| Network ID | Default 0 (0~255 optional) |
| LBT (Listen Before Talk) | Default 0: disabled, 1: enabled |
| Operating Mode | Default 1: stream mode (2: packet mode, 3: relay mode) |
| Transmission Channel | HF version defaults to 18 (corresponding to 868MHz) (0~80 is optional, corresponding to 850~930Mhz or 410~490MHz ) LF version defaults to 23 (corresponding to 433MHz) |
| Receiving Channel | HF version defaults to 18 (corresponding to 868MHz) (0~80 is optional, corresponding to 850~930Mhz or 410~490MHz ) LF version defaults to 23 (corresponding to 433MHz) |
| Address | Default 0 (0~65535 optional, 65535 is broadcast listening address) |
| Interface Selection | Default 3: RS232 (1: RS422, 2: RS485, 3: RS232 optional) |
| Interface Baud Rate | Default 9600bps (1200~115200bps optional) |
| Interface Parity | No parity by default |
- For DTU settings, please check the AddCrLf or add the carriage return line feed option. If the extension bar does not appear, click the extension button on the right to pop up. Click the +++ command button to enter the AT command mode, as shown in the figure below:
- When configuring DTU for other devices such as PLC, pay attention to the carriage return and line feed character CR LF(\r\n) at the end of the AT command.
+++\r\n Enter AT command mode AT+EXIT\r\n Exit AT command mode ATE\r\n Enable/disable AT command echo AT+VER\r\n Check the software version number AT+HELP\r\n View AT help AT+SF=7\r\n Set the spreading factor to 7, the value range is 7~12 AT+BW=0\r\n Set bandwidth, 0 means 125KHz, 1 means 250KHz, 2 means 500KHz AT+CR=1\r\n Set the encoding rate to 1, 1 represents 4/5, 2 represents 4/6, 3 represents 4/7, 4 represents 4/8 AT+PWR=22\r\n Set the RF power, the value range is 10~22dBm AT+NETID=0\r\n Network ID assignment, the value range is 0~255 AT+LBT=0\r\n Enable/disable LBT function, 0: disable, 1: enable AT+MODE=1 DTU working mode, 1: stream mode, 2: packet mode, 3: relay mode AT+TXCH=18\r\n Transmit channel, value range 0~80, corresponding frequency point is 850~930MHz or 410~490MHz AT+RXCH=18\r\n Receive channel, value range 0~80, corresponding frequency point is 850~930MHz or 410~490MHz AT+RSSI=0\r\n Enable/disable RSSI signal value output, 0: disable, 1: enable AT+ADDR=0\r\n Set DTU address, value range 0~65535 AT+PORT=3\r\n Set COM port, 1:RS422, 2:RS485, 3:RS232 AT+BAUD=9600\r\n Set COMx port baud rate, value range 9600~115200, 9600, 14400, ....., 57600, 115200 //AT+AllP is used to write AT commands at once. The sequence follows from "AT+SF" to "AT+KEY" as mentioned in the previous context. AT+AllP=7,0,1,22,0,0,1,18,18,0,0,3,115200, "8N1",0 setting spreading factor to key multiple parameters AT+RESTORE=0\r\n Restore factory settings, 0: disabled, 1: enabled
- After setting the AT parameters, entering "AT+EXIT\r\n" will save the parameters and exit AT mode. At this point, the DTU will reset. After reset, 3 seconds later, TXD and RXD will blink once to indicate that it has started working.
- Explanation of AT parameters:
- AT+SF: Configures the spreading factor of LoRa. LoRa modulation is achieved by representing each bit of payload information with multiple chips. The rate at which spread spectrum information is transmitted is called the symbol rate (Rs). The ratio between the symbol rate and the chip rate is the spreading factor, which represents the number of symbols sent per bit of information. A larger spreading factor means more information needs to be transmitted, resulting in longer transmission times. However, it also improves receiver sensitivity, making communication more likely to succeed, particularly in long-distance communication scenarios. Conversely, a smaller spreading factor has the opposite effect, requiring less time for transmission but potentially reducing sensitivity and reliability, especially in long-distance communication.
- AT+BW: Sets the bandwidth of LoRa. An increase in bandwidth results in a higher effective data rate, which reduces transmission time, but at the cost of reduced reception sensitivity, note that when using high bandwidth, the baud rate of each COMx port also needs to be increased.
- AT+CR: Configures the coding rate of LoRa. The coding rate (CR) is used to configure LoRa's error-correcting capability. A higher coding rate improves the robustness of the transmission link against noise but at the cost of longer transmission times. In normal conditions, a coding rate of 4/5 provides the best balance between error correction and transmission time. However, in the presence of strong interference, a higher coding rate can be used to enhance error correction further. The receiver does not have to know the error correcting code in advance because it is encoded in the header part of the packet.
- AT+PWR: Sets the transmission power of LoRa, affecting transmission distance. The larger the power, the larger the current consumption and the longer the transmission distance.
- AT+NETID: Establishes a LoRa mesh network, allowing the connection of multiple LoRa DTU nodes for extended transmission distance. For more details, you can refer to the relay mode.
- AT+LBT: The Listen Before Talk (LBT) for LoRa enables the device to listen for signals before transmission. When this feature is enabled (AT+LBT=1), the device monitors the channel for interference. If interference is detected, it waits for up to two seconds. If the channel is clear within these two seconds, it randomly transmits the LoRa signal. This functionality significantly enhances the reliability of communication in LoRa mesh networks by reducing the likelihood of collisions and interference.
- AT+MODE: Sets the working mode of the DTU: stream mode for plaintext transmission like Modbus ASCII, packet mode for Modbus RTU, and relay mode uses DTU as a relay node for extending transmission range.
- AT+TXCH: Set the DTU transmission channel, the range is 0~80, and the corresponding frequency point is 850~930MHz or 410~490MHz, the default factory value is 18 or 23, respectively corresponding to 868MHz or 433MHz (the HF version is 868MHz and the LF version is 433MHz).
- AT+RXCH: Set the DTU reception channel, the range is 0~80, and the corresponding frequency point is 850~930MHz or 410~490MHz, the default factory value is 18 or 23, respectively corresponding to 868MHz or 433MHz (the HF version is 868MHz and the LF version is 433MHz).
- AT+RSSI: for setting the DTU output RSSI value, after enabling (AT+RSSI=1), it will print a hexadecimal RSSI value at the back of the data every time it receives and prints a LoRa message, which can be used to evaluate the degree of LoRa signal attenuation, the bigger the value is, the further the communication distance between the two DTUs is.
Stream Transfer Mode
- DTU is in the stream mode when working in the RS485 interface (V1.2 firmware version) by default, and the factory default parameters can be used for pairing and sending.
- Stream mode refers to a transmission mode in which a LoRa device (such as SX1262-LoRa-DTU or USB-TO-LoRa) transmits the sending data stream received from an interface via LoRa to another device, which then demodulates it and outputs the data stream through the specified interface. Essentially, what is sent is what is received.
- Suppose there are Device A, B, C, D, E and F devices to form a stream mode LoRa communication network. To change the address, channel and working mode of the devices in the LoRa network, please refer to the following communication diagram and parameter table, and pay attention to using the AT command (AT+MODE=1\r\n) to switch to the stream transfer mode.
- Device A and Device C constitute stream mode point-to-point communication.
- Device A sends Hello World to Device C, and Device C with a matching address channel can receive it normally.
- Device C sends any World to Device A, and Device A with a matching address channel can receive it normally.
- Device A, B, C, D, E and F constitute stream mode point-to-multiple communication, Device B's address is set to 65535 (Hex: 0xFFFF), at this time it will be used as a device with broadcast monitoring function in the LoRa network, Device B broadcast when sending data streams, devices with addresses 0~65535 in the same channel can receive data streams, and when other devices send data streams, Device B can monitor the data streams of devices with addresses 0~65535 in the same channel.
- Device B broadcasts and sends HI World data streams, Device A, C, D and E with matching channels receive normally, and Device F with mismatched channels fails to receive.
- When Device A, C, D and E send data streams, such as Device A sends Hello World, Device B can monitor the received data streams.
- When Device F with a mismatched channel sends a data stream, Device B fails to monitor and receive.
- Device A and Device C constitute stream mode point-to-point communication.
- Suppose there are Device A, B, C, D, E and F devices to form a stream mode LoRa communication network. To change the address, channel and working mode of the devices in the LoRa network, please refer to the following communication diagram and parameter table, and pay attention to using the AT command (AT+MODE=1\r\n) to switch to the stream transfer mode.
| Parameters | Device A | Device B | Device C | Device D | Device E | Device F |
| Spreading Factor | 7 | 7 | 7 | 7 | 7 | 7 |
| Bandwidth | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz |
| Code rate | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 |
| Operating Mode | 1: Stream mode | 1: Stream mode | 1: Stream mode | 1: Stream mode | 1: Stream mode | 1: Stream mode |
| Address | 65534 (Hex:0xFFFE) | 65535 (Hex:0xFFFF) | 65534 (Hex:0xFFFE) | 65534 (Hex:0xFFFE) | 0 (Hex:0x0000) | 65534 (Hex:0xFFFE) |
| Channel | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) | 65 (Hex:0x41) |
| Example 1 | Send Hello World | √ | √ | √ | × | × |
| Example 2 | √ | Send Hi World | √ | √ | √ | × |
| Example 3 | √ | √ | Send any World | √ | × | × |
Packet Transfer Mode
- Packet mode refers to a transmission mode in LoRa devices where the first 3 bytes of the sent data stream specify the destination device address and channel. The data stream uses the hexadecimal (Hex) data format.
- Assuming there are Device A, B, C, D, E and F, a total of 6 LoRa devices forming a packet mode LoRa communication network. To modify the address, channel and working mode of the LoRa devices in the network, please refer to the communication diagram and parameter table provided below. Please note to use the AT command (AT+MODE=2\r\n) to switch to packet mode.
- Device A and Device C form a packet-mode point-to-point communication.
- Device A sends hexadecimal data stream FF FE 12 AA, where FF FE is the address of the receiving data stream device (i.e., Device C), 12 is the channel of the receiving data stream device (i.e., Device C), and AA is the data (note that the hexadecimal data format is A...F, such as AA, AF, FA, etc.), the Device C with a matching address channel receives the data normally.
- Device C sends hexadecimal data stream 00 01 12 CC, where 00 01 is the address of the receiving data stream device (i.e., Device A), 12 is the channel of the receiving data stream device (i.e., Device A), and CC is the data (note that the hexadecimal data format is A...F, such as AA, AF, FA, etc.), the Device A with a matching address channel receives the data normally.
- Device A, B, C, D, E and F form a packet mode point-to-multiple communication, Device B's address is set to 65535(Hex:0xFFFF), at this time it will be used as a broadcast listening device in the LoRa network, Device B broadcasts and sends out a data stream, the devices with the address 0~65535 under the same channel will be able to receive the stream, and when the other devices send out a stream, Device B will be able to listen to the stream of the devices with the address 0~65535 under the same channel.
- Device B broadcasts and sends a hexadecimal data stream FF FF 12 BB, where FF FF is the broadcast address, 12 is the channel, BB is the data, Device A, C, D and E (channel 18(Hex:0x12)) with matching channel receives it normally, and Device F (channel 65(Hex:0x41)) with mismatching channel fails to receive it.
- When Device A, C, D or E sends a data stream, such as Device A sends FF FE 12 AA, Device B can listen to the received data stream BB.
- When Device F (channel 65 (Hex: 0x41)) with a mismatched channel sends a data stream, Device B fails to monitor and receive.
- Device A and Device C form a packet-mode point-to-point communication.
- Assuming there are Device A, B, C, D, E and F, a total of 6 LoRa devices forming a packet mode LoRa communication network. To modify the address, channel and working mode of the LoRa devices in the network, please refer to the communication diagram and parameter table provided below. Please note to use the AT command (AT+MODE=2\r\n) to switch to packet mode.
| Parameters | Device A | Device B | Device C | Device D | Device E | Device F |
| Spreading Factor | 7 | 7 | 7 | 7 | 7 | 7 |
| Bandwidth | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz |
| Code Rate | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 |
| Operating Mode | 2: Packet transfer mode | 2: Packet transfer mode | 2: Packet transfer mode | 2: Packet transfer mode | 2: Packet transfer mode | 2: Packet transfer mode |
| Address | 65534 (Hex:0xFFFE) | 65535 (Hex:0xFFFF) | 65534 (Hex:0xFFFE) | 65534 (Hex:0xFFFE) | 0 (Hex:0x0000) | 65534 (Hex:0xFFFE) |
| Channel | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) | 65 (Hex:0x41) |
| Example 1 | Send AA (Hex) | √ | √ | √ | × | × |
| Example 2 | √ | Send BB (Hex) | √ | √ | √ | × |
| Example 3 | √ | √ | Send CC (Hex) | √ | × | × |
Relay Mode
- Relay mode refers to a transmission mode in the LoRa network where some LoRa devices act as relay nodes to forward data streams from either stream mode or packet mode. Relay mode devices do not output any data from their interfaces; their main function is to increase the wireless communication distance.
First-level Relay
- The first-level relay refers to a transmission mode in a LoRa network where multiple LoRa devices are configured, and only one LoRa device acts as a relay node to forward data streams from other LoRa devices.
- In a separate first-level relay LoRa network comprising devices A, G and H, when Device G is set as the relay mode using the AT+MODE=3\r\n command, it only relays data streams from Device A and Device H while not outputting any data streams from its interface.
- In the relay mode LoRa communication network, the communication devices in stream mode or packet mode have the same parameters except for the NETID parameter. For Device A and H, their NETID parameters will be used as addressing addresses for the relay node. For example, the NETID values of Device A and H form the address for Device G in hexadecimal: 0x0304 (Decimal: 772).
| Parameters | Device A | Device G | Device H |
| Spreading Factor | 7 | 7 | 7 |
| Bandwidth | 0: 125KHz | 0: 125KHz | 0: 125KHz |
| Code Rate | 1: 4/5 | 1: 4/5 | 1: 4/5 |
| NETID | Hex: 0x03 (Decimal: 3) | Ignore | Hex: 0x03 (Decimal: 3) |
| Operating Mode | 1: Stream Transfer Mode | 3: Relay Mode | 1: Stream Transfer Mode |
| Address | Hex: 0x0102 (Decimal: 258) | Hex: 0x0304 (Decimal: 772) | Hex: 0x0102 (Decimal: 258) |
| Channel | 18 (Hex:0x12) | 18 (Hex:0x12) | 18 (Hex:0x12) |
Second-level Relay
- Second-level relay refers to a transmission mode in a LoRa network where multiple LoRa devices are configured, and only two LoRa devices act as relay nodes to forward data streams from other LoRa devices.
- In the network depicted above, Devices A, B, C and D form a second-level relay LoRa network. After configuring Device B and C as relay mode using the AT+MODE=3\r\n command, they will only relay data streams from Device A and Device D while not outputting any data streams from their interfaces.
| Parameters | Device A | Device B | Device C | Device D |
| Spreading Factor | 7 | 7 | 7 | 7 |
| Bandwidth | 0: 125KHz | 0: 125KHz | 0: 125KHz | 0: 125KHz |
| Code Rate | 1: 4/5 | 1: 4/5 | 1: 4/5 | 1: 4/5 |
| NETID | Hex: 0x03 (Decimal: 3) | Ignore | Ignore | Hex: 0x03 (Decimal: 3) |
| Operating Mode | 1: Stream Transfer Mode | 3: Relay Mode | 3: Relay Mode | 1: Stream Transfer Mode |
| Address | Hex: 0x0102 (Decimal: 258) | Hex: 0x0304 (Decimal: 772) | Hex: 0x0405 (Decimal: 1029) | Hex: 0x0102 (Decimal: 258) |
| Channel | 18 (Hex: 0x12) | 18 (Hex: 0x12) | 18 (Hex: 0x12) | 18 (Hex: 0x12) |
Other Functions
Encryption
- The encryption feature encrypts plaintext data from LoRa devices using the AES algorithm before transmission over LoRa, ensuring wireless communication security.
- To set up encryption, use the AT+KEY=65535 command (default 0: encryption disabled, 1~65535: key value) to configure the encryption key.
- After enabling encryption, LoRa devices with the same key value can communicate normally, while LoRa devices with different key values cannot establish a successful communication link.
- As shown in the diagram, when Device A and B have the same encryption key, they can communicate normally. However, when the key value is different, as in the case of Device C, the data output appears as garbled or unreadable.
RSSI Output
- RSSI, Received signal strength indication, used to evaluate signal quality, improve communication network, distance measurement, etc.
- After using AT+RSSI=1 (default 0: disabled) to enable the RSSI function, as shown in the figure below, each output data packet will follow a hexadecimal RSSI value.
LBT (Listen Before Talk)
- LBT (Listen Before Talk) means that the module actively monitors the channel environment noise before sending. This function can improve the communication success rate and anti-collision processing of DTU in harsh environments.
- Use AT+LBT=1 (default 0: disabled) to enable the LBT function, and actively monitor the channel noise before sending the data packet, if it exceeds the threshold, the sending will be delayed, the maximum delay is two seconds, and the sending will be forced after more than two seconds.
Upgrade Firmware
- The default firmware update interface is RS485, other interfaces are not supported.
- Press and hold the KEY button within three seconds after powering on, and release the KEY button when the TXD and RXD lights are on simultaneously. After entering the firmware update mode, use a USB to RS485 tool (such as USB TO RS485) to connect DTU and PC.
- Download and open the firmware update software, open the corresponding COM, select the latest firmware such as SX1262-LoRa-DTU-HF-V1.1.ws, and click the Update button to update.
- Power on the device after the upgrade.
Resource
Datasheet
Software
Others
FAQ
Answer:
KEY: Note, do not press the key within 3 seconds of power-on. Within 3 seconds of power-on, press and hold the key for 2 seconds to enter firmware update mode (V1.1 firmware start). After 3 seconds of power-on, TAP the KEY button to switch among RS485, RS232 and RS422.
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Answer:
- 1) Consider that the amount of data sent per unit of time is too large.
240 characters can be sent in one second, it is recommended to reduce the amount of data and sending frequency. - 2) Firmware problem, please burn the latest firmware comparison test:
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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.
Working Time: 9 AM - 6 PM GMT+8 (Monday to Friday)