# AT LoRa USB Dongle

USB device that lets you send and receive LoRa wireless data using simple AT commands. No coding needed. Good for testing and development.

- **Seller:** [Ropixon Labs](https://lectronz.com/stores/ropixon), Choceň, Březenice, Czechia
- **Price:** €78.00 (EUR, before shipping and taxes)
- **Availability:** In stock
- **Categories:** STM32, Prototyping, Tools
- **Product page:** https://lectronz.com/products/at-lora-usb-dongle

## Options

**Oscilator type**

- RF with XTALL [Add €39.00] (10 left)
- RF with TCXO [Add €44.00] (1 left)

## Links

- [Documentation](https://github.com/Ropixon/AT-LoRa-USB-Dongle)
- [Design Files](https://github.com/Ropixon/AT-LoRa-USB-Dongle/tree/master/Hardware)
- [Schematics](https://github.com/Ropixon/AT-LoRa-USB-Dongle/tree/master/Hardware)

## Images

![AT LoRa USB Dongle](https://lectronz-images.b-cdn.net/lectronz/active_storage/representations/proxy/eyJfcmFpbHMiOnsiZGF0YSI6NDMyNzQsInB1ciI6ImJsb2JfaWQifX0=--7945359f9f7a50f8f7ba59311cfe6882cb6d3a36/eyJfcmFpbHMiOnsiZGF0YSI6eyJmb3JtYXQiOiJqcGciLCJyZXNpemVfdG9fbGltaXQiOls5NjAsNjQwXSwic2F2ZXIiOnsic3RyaXAiOnRydWV9fSwicHVyIjoidmFyaWF0aW9uIn19--970c165836a83091725a1a0fd4f37ce9408da1bf/22_clean.jpg)
![AT LoRa USB Dongle](https://lectronz-images.b-cdn.net/lectronz/active_storage/representations/proxy/eyJfcmFpbHMiOnsiZGF0YSI6NDMyNzEsInB1ciI6ImJsb2JfaWQifX0=--dfc0bb96279c98ac598dd8ab8ef328cba5e7b028/eyJfcmFpbHMiOnsiZGF0YSI6eyJmb3JtYXQiOiJqcGciLCJyZXNpemVfdG9fbGltaXQiOls5NjAsNjQwXSwic2F2ZXIiOnsic3RyaXAiOnRydWV9fSwicHVyIjoidmFyaWF0aW9uIn19--970c165836a83091725a1a0fd4f37ce9408da1bf/44_clean.jpg)
![AT LoRa USB Dongle](https://lectronz-images.b-cdn.net/lectronz/active_storage/representations/proxy/eyJfcmFpbHMiOnsiZGF0YSI6NDMyNzksInB1ciI6ImJsb2JfaWQifX0=--fe34883a370d070b9e526f02442c037f2a1f32ea/eyJfcmFpbHMiOnsiZGF0YSI6eyJmb3JtYXQiOiJwbmciLCJyZXNpemVfdG9fbGltaXQiOls5NjAsNjQwXSwic2F2ZXIiOnsic3RyaXAiOnRydWV9fSwicHVyIjoidmFyaWF0aW9uIn19--605f1da017bcbb03ce31845cd0e81d97e3b3c574/clean_3.png)
![AT LoRa USB Dongle](https://lectronz-images.b-cdn.net/lectronz/active_storage/representations/proxy/eyJfcmFpbHMiOnsiZGF0YSI6NDMyODMsInB1ciI6ImJsb2JfaWQifX0=--589735ccf20d83b02cc34150f81c71a3e4d4f75e/eyJfcmFpbHMiOnsiZGF0YSI6eyJmb3JtYXQiOiJwbmciLCJyZXNpemVfdG9fbGltaXQiOls5NjAsNjQwXSwic2F2ZXIiOnsic3RyaXAiOnRydWV9fSwicHVyIjoidmFyaWF0aW9uIn19--605f1da017bcbb03ce31845cd0e81d97e3b3c574/1_clean.png)

## Description

## What is AT LoRa Dongle?

**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.

**For quick start:**

**1)** Install driver for serial interface CP2102 according to your system: [Download drivers](https://www.silabs.com/interface/usb-bridges/classic/device.cp2102?tab=softwareandtools)
 
**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:

- RED => Reception of new AT commands
- GREEN => System LED - indicates proper operation of the entire device
- BLUE => Reception or transmission of LoRa data


*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 **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:
- **RF LoRa Chip**: SX1262 LoRa transceiver from Semtech - Datasheet here: [SX1262](https://www.semtech.com/products/wireless-rf/lora-connect/sx1262)
- **Interface**: USB (Virtual COM port) - Drivers can be found here: [Download drivers](https://www.silabs.com/interface/usb-bridges/classic/device.cp2102?tab=softwareandtools)
- **Control**: AT commands via serial line
- **Supported baud rates**: 9600, 19200, 38400, 57600, 115200, 230400 (default/recommended)
- **Frequency**: 150 MHz - 960 MHz (typically **863-870 MHz for EU, 915 MHz for USA)**, RF path is optimized for 868 MHz band, but 915 MHz operation is also fine. The further from the operating band, the less power can be transmitted/received from the dongle.
- **TX power**: up to **22 dBm**
- **Spreading Factor**: SF5 to SF12
- **Bandwidths**: 7.81 kHz to 500 kHz

## Serial terminal connection configuration:
- **Baud rate**: 230400 (default)
- **Data bits**: 8
- **Parity**: None
- **Stop bits**: 1
- **Flow control**: None
- **Line ending**: CR+LF (\r\n)

## Communication test
Send command:
```
AT (or AT+HELP)
```
Dongle will respond with a list of all available commands.
```
AT+IDENTIFY
```
Dongle will respond "Ropixon AT-USB LoRa_Dongle v1.0.0 UID:xxxxxxx......."

---

## AT Commands - Complete Overview

### Basic 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 all settings to factory defaults and restart | `AT+FACTORY_RST` |
| `AT+SYS_RESTART` | System restart | `AT+SYS_RESTART` |
| `AT+UART_BAUD` | Set/query baud rate, restart on change | `AT+UART_BAUD=230400` |

### LoRa TX Parameters (transmission)

| Command | Description | Value Range | Example |
|---------|-------------|-------------|---------|
| `AT+LR_TX_FREQ` | TX frequency in Hz | - | `AT+LR_TX_FREQ=869525000` |
| `AT+LR_TX_POWER` | TX power | -17 to 22 dBm | `AT+LR_TX_POWER=14` |
| `AT+LR_TX_SF` | Spreading Factor | 5 to 12 | `AT+LR_TX_SF=7` |
| `AT+LR_TX_BW` | Bandwidth | 0-9 (see table) | `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, 1 | `AT+LR_TX_CRC=1` |
| `AT+LR_TX_IQ` | IQ inversion | 0, 1 | `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 Optimization | 0=off, 1=on, 2=auto | `AT+LR_TX_LDRO=2` |

## LoRa RX Parameters (reception)

Same parameters as TX, just replace `TX` with `RX`:
- `AT+LR_RX_FREQ`, `AT+LR_RX_SF`, `AT+LR_RX_BW`, etc.

**Important**: `AT+LR_RX_PLDLEN` - Payload length (required for implicit header mode)

### Bandwidth Values

| Value | Bandwidth |
|-------|-----------|
| 0 | 7.81 kHz |
| 1 | 10.42 kHz |
| 2 | 15.63 kHz |
| 3 | 20.83 kHz |
| 4 | 31.25 kHz |
| 5 | 41.67 kHz |
| 6 | 62.5 kHz |
| 7 | 125 kHz |
| 8 | 250 kHz |
| 9 | 500 kHz |

## Quick Setup (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
```


**How to navigate all parameter configurations?** 
Here is calculator showing what happens to data/packet with different modulation settings
(select SX1262 as device):

- Online calculator: [Semtech LoRa Calculator](https://www.semtech.com/design-support/lora-calculator)
- Offline calculator (PDF): [Semtech SX1262 Calculator](https://semtech.my.salesforce.com/sfc/p/E0000000JelG/a/2R000000Q2OT/GhbZe2lGVNO6sNDUlo6lcHVaKMQvcVCdaYfFeSjyitk)

A simple rule applies:
For high data rates, choose high BW and low SF - however, this reduces the receiver's ability to obtain data at greater distances. On the other side, if signal is weak (poor transmission conditions) **SF** needs to be increased and **BW** decreased. All this affects packet Time on Air (TOA). TOA can also be easily verified using the command: `AT+RF_GET_TOA=<packet_size_bytes>`, the result is calculated from the current LoRa TX settings.
### 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 to UART | `AT+RF_RX_TO_UART=1` |
| `AT+RF_RX_FORMAT` | RX data output format | `AT+RF_RX_FORMAT=HEX` |

**Received data is displayed automatically** (if `RX_TO_UART=1 (ON), =0 (OFF), ?`

Received data output format:

```
+RX:5,48656C6C6F,RSSI:-45
```
Where **5** = number of received bytes, **48656C6C6F** = packet itself, **-45** = packet RSSI

### Saved Packets and Periodic Transmission
One packet can be stored in the **AT dongle** (NVM memory), which can then be sent at any time or set for 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 saved packet TX period | `AT+RF_TX_NVM_PERIOD=1000` |
| `AT+RF_TX_PERIOD_STATUS` | Current periodic TX status | `AT+RF_TX_PERIOD_STATUS?` |

### RF Test Commands
For various testing purposes, these 3 commands may be useful, especially `AT+RF_TX_CW=1 (ON), =0 (OFF), ?`, which enables carrier wave transmission (no modulated data).

| Command | Description | Example |
|---------|-------------|---------|
| `AT+RF_TX_CW` | Enable/disable CW (continuous wave) transmission | `AT+RF_TX_CW=1` |
| `AT+RF_GET_TOA` | Calculate Time on Air from current TX settings, parameter is packet length in bytes | `AT+RF_GET_TOA=10` |
| `AT+RF_GET_TSYM` | Get symbol time from current TX settings | `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` (pin 1, 1Hz, duty 50%) |
| `AT+AUX_PULSE_STOP` | Stop PWM | `AT+AUX_PULSE_STOP=1` (stop PWM on pin 1) |

---

## Practical Usage Examples

### Example 1: Simple Point-to-Point Communication

**Dongle 1 (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
```

**Dongle 2 (receiver):**

```
AT+LR_RX_SET=SF:9,BW:7,CR:45,Freq:869525000,IQInv:0,HeaderMode:0,CRC:1,Preamble:8,LDRO:2
```

→ Receiver will output: `+RX:4,AABBCCDD,RSSI:-47`

### Example 2: Range Test with Periodic Transmission

**TX Dongle:**
```
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
```

Subsequent RX reception:
`+RX:5,1122334455,RSSI:-68`

### Example 3: CW Test on Frequency

```
AT+LR_TX_FREQ=868000000
AT+LR_TX_POWER=10
AT+RF_TX_CW=1
```
Transmits carrier wave at 868 MHz with 10 dBm power

Stop TX:
```
AT+RF_TX_CW=0
```

### Example 4: Baud Rate Change

**Query current speed:**
```
AT+UART_BAUD?
```
115200

**Change to faster:**
```
AT+UART_BAUD=230400
OK
```
Dongle restarts and switches to **230400** baud. Terminal must also be switched.

---

## Important Notes

### TX/RX Parameter Compatibility

**For successful communication, RF settings must match:**

- 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)**
- LDRO **(LDRO 2 = automatic mode)**
- IQInv **(TX_IQInv = RX_IQInv)**

### Range vs. Speed Optimization

**Maximum range (lowest speed):**
High SF and low BW → maximum range → slowest data rate

- **SF:** 12
- **BW:** 0 (7.81 kHz)
- **CR:** 48 (4/8)
- **Power:** 22 dBm
- → Range: > 10 km (open space)

**High speed (shorter range):**

- **SF:** 5
- **BW:** 9 (500 kHz)
- **CR:** 45 (4/5)
- **Power:** 22 dBm


### Time on Air (ToA)

The higher the SF and lower the BW, the longer the transmission time. Use `AT+RF_GET_TOA` to get packet time on air.

### Implicit vs. Explicit Header

- **Explicit (0)**: Header contains packet length
- **Implicit (1)**: No header - RX_PLDLEN must be set on receiver side before starting reception!

### LDRO (Low Data Rate Optimization)

- **Auto (2)**: Firmware automatically selects based on SF and BW - **recommended**
- **On (1)**: Manually enabled - you can experiment and select suitable option for your settings
- **Off (0)**: Manually disabled

---

## Troubleshooting

### Dongle is not responding to AT commands

**1.** Check baud rate (try 115200 or 230400)
**2.** Check connection jumpers on serial line **MCU-USB** must be connected on both RX and TX headers
**3.** Check line ending (must be CR+LF)
**4.** Restart dongle (disconnect and reconnect USB)
**5.** Try `AT+SYS_RESTART`

### RX not seeing TX data

**1.** Verify all RF parameters for TX and RX are identical
**2.** Verify RX has enabled `AT+RF_RX_TO_UART=1`
**3.** Increase TX power or shorten distance

### Low RSSI or Packet Loss

**1.** Increase TX power (**max 22 dBm**)
**2.** Reduce distance
**3.** Try higher SF (7→9→12)
**4.** Try connecting external antenna - need to resolder jumper (zero ohm resistor in 0402 package) from chip antenna to UFL connector!!

### CRC Errors

**1.** RF interference - change frequency
**2.** TX/RX parameter mismatch
**3.** Set LDRO to "auto" on both TX and RX sides

---

## Technical Specifications

### Hardware

- **MCU**: STM32L071 (ARM Cortex-M0+)
- **RF chip**: Semtech SX1262
- **Frequency**: 150 MHz - 960 MHz
- **TX power**: 0 to +22 dBm
- **RX sensitivity**: up to -149.1 dBm (SF12, BW 7.81 kHz)
- **USB**: Virtual COM port
- **GPIO**: 8x AUX pins (PWM capable)

### Operating Conditions

- **Power supply**: 5V from USB
- **Temperature**: -20°C to +70°C (operating)

**© 2024-2026 Ropixon - AT LoRa Dongle**