Source: https://mokxi.com/parts/sx1278 Updated: 2026-11-02 Part # LoRa module, SX1278 (Ra-02) Put two down and they talk: LoRa.h or RadioLib, packets that take as long on the air as real ones, on a shared air line. or see every part - 14 pins - In 1 project Drawn live by the editor's own code, at the size you see it. At a glance ## The LoRa module, SX1278 (Ra-02) in brief What it is, and where it sits on the bench. The Ai-Thinker Ra-02 is a Semtech SX1278 LoRa radio for 433 MHz on a shielded board; the SX1276 in the RFM95W has the same registers, so this part covers it too. Its pins are GND, 3.3V, RST, DIO0 to DIO5, NSS, SCK, MISO and MOSI, on 1.8 to 3.7 V, never 5 V. With LoRa.h’s defaults on an Uno, NSS goes to 10, RST to 9, DIO0 to 2 and SPI to 13, 11 and 12 and power from 3V3; on an ESP32, SCK, MISO and MOSI go to GPIO 18, 19 and 23 and LoRa.setPins() names the rest. Mokxi models the datasheet’s register file behind SPI, RegVersion reading 0x12, with its modes, FIFO, IRQ flags, DIO0 and DIO1. Every module’s extra ANT pin joins one shared air, so two modules hear each other with no wire, and packets take LoRa’s real time on air: about 60 ms for 20 bytes at SF7 and 125 kHz, over a second at SF12. A receiver takes only packets whose frequency, sync word, spreading factor and bandwidth match. The classic mistake is changing one on one side only. Distance, walls and fading are not modeled; RSSI always reads -45 dBm. Family Clocks and links Pins 14 Pins ## 14 pins Named as the editor names them, so a wire lands where you expect it. Pin Role What it does GND Input or output Ground. 3.3V Input or output Supply, 1.8 to 3.7 V. Use the board's 3.3 V pin. RST Input Reset, active low. DIO0 Output Packet received, packet sent or channel scan done, as the sketch maps it. DIO1 Output Receive timeout. DIO2 to DIO5 stay low. DIO2 Output DIO3 Output DIO4 Output DIO5 Output NSS Input SPI chip select. SCK Input SPI. MISO Output SPI. MOSI Input SPI. ANT Input or output The air every LoRa module on the canvas shares. Leave it unwired. How to use it ## How to use the SX1278 Ra-02 LoRa module with an Arduino The Ra-02 is a 3.3 V SPI radio. With LoRa.h’s default pins on an Uno, NSS goes to 10, RST to 9 and DIO0 to 2, SCK, MISO and MOSI to 13, 12 and 11, and the supply to the 3V3 pin, never 5V. This messenger wires two Unos that way, one module each, and no wire between the modules: every LoRa module on the canvas shares one air. LoRa.begin(433E6) finds the chip, then beginPacket(), print() and endPacket() send, and parsePacket() and read() receive. The sender prints each packet’s time on air, a few tens of milliseconds at the default spreading factor of 7; call LoRa.setSpreadingFactor(12) in both sketches and it is close to a second. Change it, the frequency or the sync word on one side only and nothing arrives. On the bench, the Uno’s 5 V SPI lines want level shifting in front of a 3.3 V chip. Part pin Board pin 3.3V 3V3 GND GND NSS Pin 10 RST Pin 9 DIO0 Pin 2 SCK Pin 13 MISO Pin 12 MOSI Pin 11 An ESP32 is 3.3 V throughout: put SCK, MISO and MOSI on GPIO 18, 19 and 23 and call LoRa.setPins() with your NSS, RST and DIO0 before LoRa.begin(). Click to open it in the editor This is the simulator itself, running here. Click anything to open it in the editor. Open this project in the editor Read the full tutorial The sending end, from the LoRa messenger How it is modeled ## What is true about the LoRa module, SX1278 (Ra-02), here In its help article’s own words: what the simulation gets right, and where it stops. ### Not modeled The radio itself: distance, walls, fading and output power. packetRssi() and getRSSI() always report -45 dBm and packetSnr() 9.5 dB, a strong close signal, because there is no distance in the simulator. The coding rate is stored but does not change the time on air, and modules with different coding rates still hear each other. Invert IQ and implicit header mode are stored and not modeled. The FSK modem is not modeled: in FSK mode nothing is sent or heard. There is no LoRaWAN gateway or network server, so LMIC and The Things Network sketches have nobody to join. From LoRa module, SX1278 (Ra-02), in full. Projects ## See the LoRa module, SX1278 (Ra-02) in a project One built-in project uses it. It opens in the editor, already wired. Boards ## The boards it is shown on This board has a built-in project with the LoRa module, SX1278 (Ra-02) in it. - Arduino Uno R3 Libraries ## Arduino libraries for the LoRa module, SX1278 (Ra-02) Built in, so the sketch compiles with nothing to install. Each page has the calls, the wiring and an example to run. - LoRa - RadioLib More parts ## The rest of the bench Every one of these is drawn and simulated the same way. Full-size breadboard A real 0.1 inch grid with the rails and the center channel, 63 columns wide. Jumper wires Drag from any pin or hole to any other. Corners snap, and you can drag them. Power A supply rail at the voltage you choose. Ground The other end of every circuit. LED Lights when current flows. Five colors, and the brightness is what your eye would see. Filament lamp A tungsten bulb in a holder: an inrush when it is switched on cold, tens of milliseconds to warm up, and dim on half its voltage. Resistor Any value you like, with the color bands drawn to match. ESP32-C3-DevKitM-1 A RISC-V board that runs your firmware at 160 MHz on the real memory map. Pushbutton A 12 mm tactile switch. Hold it while the simulation runs. Raspberry Pi Pico The RP2040 board on our own Cortex-M0+ core. Pick a program and press Run. Raspberry Pi Pico W Raspberry Pi Pico W (RP2040). The same board and the same pinout as a Pico, with the CYW43439 on it. The WiFi is simulated (no radio; real internet through the Cloud panel’s switch), and the on-board LED, which hangs off that chip rather than off GP25, is driven through the same path. Everything else is the Pico. Raspberry Pi 4 Model B Raspberry Pi 4 Model B: the 40-pin header, driven by main.py with RPi.GPIO or gpiozero. See every part ## Wire up the LoRa module, SX1278 (Ra-02) Open the editor and push it into the breadboard. It is free, and it runs on your own machine. Start building free Open the editor