RopixonRopixon AT LoRa Dongle - User Manual
Ropixon AT-USB LoRa Dongle enables sending and receiving all LoRa packets! Just configure it properly using intuitive AT commands via serial line.
- No programming required.
- It's suitable for rapid development, testing, or creating your own wireless LoRa link.
What is it for?
AT LoRa Dongle is suitable for:
- Testing and development of LoRa applications
- Point-to-Point communication over long distances
- Range tests - measuring capable of LoRa connection distance
- Sensor networks - collecting data from remote sensors
- RF testing - testing RF parameters, CW transmission
- Scanning - capturing random packets transmitted over the air
Overview
When sending packets, no additional "wrapping" or encryption of data is used - you always send RAW (hex or ASCII) data. The same applies to reception.
Additional functions: AT LoRa dongle has 8 aux pins - you can set its logical level or activate PWM on it - just through the AT commands.
AT LoRa Dongle - hardware overview
For quick start:
Ready-to-use device available on Tindie.
1) Install driver for serial interface CP2102 according to your system: Download drivers
2) Connect AT dongle to USB and set desired LoRa parameter configuration (or leave defaults)
3) Send your first LoRa packet via AT commands:
- Send data in ASCII:
AT+RF_TX_TXT=Hello, this is AT LoRa dongle Ropixon! - Send data in HEX:
AT+RF_TX_HEX=48656C6C6F2C2074686973206973204154204C6F526120646F6E676C6520526F7069786F6E21
4) Reception is activated automatically - output format HEX/ASCII can be selected using AT+RF_RX_FORMAT=HEX|ASCII, ?
Status LEDs
The dongle has 3 LEDs serving these functions:
| LED | Function |
|---|---|
| 🔴 RED | Reception of new AT commands |
| 🟢 GREEN | System LED - indicates proper operation |
| 🔵 BLUE | Reception or transmission of LoRa data |
Aux pins
The AT dongle has 8 aux pins that can be "manually" controlled or run PWM modulation (maximum frequency 1 kHz): AT+AUX_PULSE=<pin:1-8>,<period_ms>,<duty%:0-100>
Main Features
| Feature | Specification |
|---|---|
| RF LoRa Chip | SX1262 LoRa transceiver from Semtech (Datasheet) |
| Interface | USB (Virtual COM port) |
| Control | AT commands via serial line |
| Baud rates | 9600, 19200, 38400, 57600, 115200, 230400 (default) |
| Frequency | 150 MHz - 960 MHz (optimized for 868 MHz band) |
| TX power | 0 to +22 dBm |
| Spreading Factor | SF5 to SF12 |
| Bandwidths | 7.81 kHz to 500 kHz |
Note: RF path is optimized for 868 MHz band (EU: 863-870 MHz, USA: 915 MHz). The further from the operating band, the less power can be transmitted/received.
AUX Pins
The dongle has 8 auxiliary pins that can be manually controlled or run PWM modulation (max frequency 1 kHz):
AT+AUX_PULSE=<pin:1-8>,<period_ms>,<duty%:0-100>
Quick Start
1. Install driver according to your system: Download drivers
2. Connect AT dongle to USB and set desired LoRa parameter configuration (or leave defaults)
3. Send data via AT commands:
- ASCII:
AT+RF_TX_TXT=Hello, this is AT LoRa dongle Ropixon! - HEX:
AT+RF_TX_HEX=48656C6C6F2C2074686973206973204154204C6F526120646F6E676C6520526F7069786F6E21
4. Reception is activated automatically - output format can be selected using AT+RF_RX_FORMAT=HEX or AT+RF_RX_FORMAT=ASCII
Use Cases
- Testing and development of LoRa applications
- Point-to-Point communication over long distances
- Range tests - measuring LoRa connection range
- Sensor networks - collecting data from remote sensors
- RF testing - testing RF parameters, CW transmission
- Scanning - capturing packets transmitted over the air
Serial Connection
| Parameter | Value |
|---|---|
| Baud rate | 230400 (default) |
| Data bits | 8 |
| Parity | None |
| Stop bits | 1 |
| Flow control | None |
| Line ending | CR+LF (\r\n) |
Communication Test
Send AT or AT+HELP - dongle will respond with a list of all available commands.
Send AT+IDENTIFY - dongle will respond with device identification:
Ropixon AT-USB LoRa_Dongle v1.0.0 UID:xxxxxxx.......
AT Commands Reference
System Commands
| Command | Description | Example |
|---|---|---|
AT | Print help | AT |
AT+HELP | Display all available commands | AT+HELP |
AT+IDENTIFY | Return unique device ID | AT+IDENTIFY |
AT+FACTORY_RST | Reset to factory defaults and restart | AT+FACTORY_RST |
AT+SYS_RESTART | System restart | AT+SYS_RESTART |
AT+UART_BAUD | Set/query baud rate (restarts on change) | AT+UART_BAUD=230400 |
LoRa TX Parameters
| Command | Description | Values | Example |
|---|---|---|---|
AT+LR_TX_FREQ | TX frequency in Hz | 150-960 MHz | AT+LR_TX_FREQ=869525000 |
AT+LR_TX_POWER | TX power | 0 to +22 dBm | AT+LR_TX_POWER=14 |
AT+LR_TX_SF | Spreading Factor | 5-12 | AT+LR_TX_SF=7 |
AT+LR_TX_BW | Bandwidth | 0-9 (see table below) | AT+LR_TX_BW=7 |
AT+LR_TX_CR | Coding Rate | 45, 46, 47, 48 | AT+LR_TX_CR=45 |
AT+LR_TX_PREAMBLE | Preamble length | symbols | AT+LR_TX_PREAMBLE=8 |
AT+LR_TX_SYNCWORD | Sync word | 0x0000-0xFFFF | AT+LR_TX_SYNCWORD=0x3444 |
AT+LR_TX_CRC | CRC enable/disable | 0=off, 1=on | AT+LR_TX_CRC=1 |
AT+LR_TX_IQ | IQ inversion | 0=off, 1=on | AT+LR_TX_IQ=0 |
AT+LR_TX_HEADERMODE | Header mode | 0=explicit, 1=implicit | AT+LR_TX_HEADERMODE=0 |
AT+LR_TX_LDRO | Low Data Rate Opt. | 0=off, 1=on, 2=auto | AT+LR_TX_LDRO=2 |
LoRa RX Parameters
Same parameters as TX, replace TX with RX in command names: AT+LR_RX_FREQ, AT+LR_RX_SF, AT+LR_RX_BW, etc.
Important:AT+LR_RX_PLDLEN- Payload length is required for implicit header mode.
Bandwidth Reference
| Value | Bandwidth | Value | Bandwidth | |
|---|---|---|---|---|
| 0 | 7.81 kHz | 5 | 41.67 kHz | |
| 1 | 10.42 kHz | 6 | 62.5 kHz | |
| 2 | 15.63 kHz | 7 | 125 kHz | |
| 3 | 20.83 kHz | 8 | 250 kHz | |
| 4 | 31.25 kHz | 9 | 500 kHz |
Quick Setup Commands
Configure all RF parameters at once:
TX configuration:
AT+LR_TX_SET=SF:7,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2,Power:22
RX configuration:
AT+LR_RX_SET=SF:7,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2
Tip: Use Semtech LoRa Calculator (select SX1262) to understand how different modulation settings affect your data/packet.
Simple rule: High BW + low SF = faster data rate but shorter range. Low BW + high SF = longer range but slower. Use AT+RF_GET_TOA=<packet_size> to check Time on Air.
RF Transmission and Reception
| Command | Description | Example |
|---|---|---|
AT+RF_TX_HEX | Transmit data in HEX format | AT+RF_TX_HEX=48656C6C6F |
AT+RF_TX_TXT | Transmit data as text | AT+RF_TX_TXT=Hello |
AT+RF_RX_TO_UART | Enable/disable RX output | AT+RF_RX_TO_UART=1 |
AT+RF_RX_FORMAT | RX data output format | AT+RF_RX_FORMAT=HEX |
Received data format:
+RX:<length>,<data>,RSSI:<rssi>
Example: +RX:5,48656C6C6F,RSSI:-45 (5 bytes, data "Hello" in hex, RSSI -45 dBm)
Saved Packets and Periodic Transmission
Store one packet in NVM memory for later or periodic transmission:
| Command | Description | Example |
|---|---|---|
AT+RF_SAVE_PACKET | Save packet to memory | AT+RF_SAVE_PACKET=010203 |
AT+RF_TX_SAVED | Transmit saved packet once | AT+RF_TX_SAVED |
AT+RF_TX_SAVED_REPEAT | Start/stop periodic TX | AT+RF_TX_SAVED_REPEAT=ON |
AT+RF_TX_NVM_PERIOD | Set TX period in ms | AT+RF_TX_NVM_PERIOD=1000 |
AT+RF_TX_PERIOD_STATUS | Query periodic TX status | AT+RF_TX_PERIOD_STATUS? |
RF Test Commands
| Command | Description | Example |
|---|---|---|
AT+RF_TX_CW | Continuous wave (carrier only) | AT+RF_TX_CW=1 |
AT+RF_GET_TOA | Calculate Time on Air (ms) | AT+RF_GET_TOA=10 |
AT+RF_GET_TSYM | Get symbol time | AT+RF_GET_TSYM |
AUX GPIO Pins (1-8)
| Command | Description | Example |
|---|---|---|
AT+AUX | Set pin state | AT+AUX=1,1 (pin 1 HIGH) |
AT+AUX_PULSE | Start PWM | AT+AUX_PULSE=1,1000,50 (1 Hz, 50% duty) |
AT+AUX_PULSE_STOP | Stop PWM | AT+AUX_PULSE_STOP=1 |
Practical Examples
Example 1: Point-to-Point Communication
Transmitter:
AT+LR_TX_SET=SF:9,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,Power:22,LDRO:2 AT+RF_TX_HEX=AABBCCDD
Receiver:
AT+LR_RX_SET=SF:9,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2
Receiver output: +RX:4,AABBCCDD,RSSI:-47
Example 2: Range Test with Periodic TX
TX Dongle (sends packet every 2 seconds):
AT+LR_TX_SET=SF:12,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2,Power:22 AT+RF_SAVE_PACKET=31313232333334343535 AT+RF_TX_NVM_PERIOD=2000 AT+RF_TX_SAVED_REPEAT=ON
RX Dongle:
AT+LR_RX_SET=SF:12,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2 AT+RF_RX_TO_UART=1 AT+RF_RX_FORMAT=ASCII
Output: +RX:10,1122334455,RSSI:-68
Example 3: CW Test
Transmit carrier wave at 868 MHz with 10 dBm:
AT+LR_TX_FREQ=868000000 AT+LR_TX_POWER=10 AT+RF_TX_CW=1
Stop: AT+RF_TX_CW=0
Example 4: Change Baud Rate
AT+UART_BAUD? → 115200 AT+UART_BAUD=230400 → OK (dongle restarts)
Note: Update your terminal to the new baud rate after restart.
Important Notes
TX/RX Parameter Compatibility
For successful communication, these RF settings must match on both sides:
| Parameter | TX = RX |
|---|---|
| Frequency | TX_FREQ = RX_FREQ |
| Spreading Factor | TX_SF = RX_SF |
| Bandwidth | TX_BW = RX_BW |
| Coding Rate | TX_CR = RX_CR |
| Sync Word | TX_SYNCWORD = RX_SYNCWORD |
| Header Mode | TX_HEADERMODE = RX_HEADERMODE |
| CRC | TX_CRC = RX_CRC |
| IQ Inversion | TX_IQ = RX_IQ |
| LDRO | Use 2 (auto) on both sides |
Range vs. Speed Optimization
| Setting | Maximum Range | Maximum Speed |
|---|---|---|
| SF | 12 | 5 |
| BW | 0 (7.81 kHz) | 9 (500 kHz) |
| CR | 48 (4/8) | 45 (4/5) |
| Power | 22 dBm | 22 dBm |
| Result | > 10 km (open space) | Fastest data rate |
Header Modes
| Mode | Value | Description |
|---|---|---|
| Explicit | 0 | Header contains packet length (recommended) |
| Implicit | 1 | No header - RX_PLDLEN must be set on receiver! |
LDRO (Low Data Rate Optimization)
| Value | Description |
|---|---|
| 0 | Off (manual) |
| 1 | On (manual) |
| 2 | Auto (recommended) - firmware selects based on SF/BW |
Troubleshooting
Dongle Not Responding
- Check baud rate (try 115200 or 230400)
- Verify MCU-USB jumpers are connected on both RX and TX headers
- Check line ending (must be CR+LF)
- Reconnect USB cable
- Try
AT+SYS_RESTART
RX Not Receiving Data
- Verify all RF parameters match between TX and RX
- Enable RX output:
AT+RF_RX_TO_UART=1 - Increase TX power or reduce distance
Low RSSI / Packet Loss
- Increase TX power (max 22 dBm)
- Reduce distance
- Increase SF (7 → 9 → 12)
- Use external antenna (requires resoldering 0402 jumper from chip antenna to U.FL connector)
CRC Errors
- Change frequency (RF interference)
- Verify TX/RX parameter match
- Set LDRO to
2(auto) on both sides
Technical Specifications
| Component | Specification |
|---|---|
| MCU | STM32L071 (ARM Cortex-M0+) |
| RF chip | Semtech SX1262 |
| Frequency | 150 MHz - 960 MHz |
| TX power | 0 to +22 dBm |
| RX sensitivity | -149.1 dBm (SF12, BW 7.81 kHz) |
| USB | Virtual COM port (CP2102) |
| GPIO | 8x AUX pins (PWM capable) |
| Power supply | 5V from USB |
| Operating temp. | -20°C to +70°C |
Appendix: Python Automation
Example script using pyserial for automated testing:
#!/usr/bin/env python3
import serial
import time
# Configuration
PORT = "COM3" # Windows: COM3, Linux: /dev/ttyUSB0
BAUD = 230400
FREQ = 869525000
DATA_HEX = "48656C6C6F" # "Hello"
def send_AT(ser, cmd, timeout=2.0): """Send AT command and wait for response.""" ser.reset_input_buffer() ser.write((cmd + "\r\n").encode())
t0, resp = time.time(), "" while time.time() - t0 < timeout: if ser.in_waiting: resp += ser.read(ser.in_waiting).decode(errors="ignore") if "OK" in resp or "ERROR" in resp: break time.sleep(0.01) return resp.strip()
# Main
ser = serial.Serial(PORT, BAUD, timeout=1)
time.sleep(0.5)
# Verify device
resp = send_AT(ser, "AT+IDENTIFY")
if "Ropixon AT-USB LoRa_Dongle" not in resp: print(f"Unknown device: {resp}") ser.close() exit(1)
print(resp)
# Configure and send
send_AT(ser, f"AT+LR_TX_SET=SF:7,BW:7,CR:45,Freq:{FREQ},IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2,Power:22")
for i in range(5): resp = send_AT(ser, f"AT+RF_TX_HEX={DATA_HEX}", timeout=3.0) print(f"Packet {i+1}: {'OK' if 'OK' in resp else 'FAIL'}") time.sleep(1.0)
ser.close()