LoRa SX1278 Not working with Arduino UNO

Projects Networking, Protocols, and Devices
1

Hi
I am trying to setup a basic LoRa communication between two Arduino UNO boards and SX1278, 433MHz modules, one as RX and other as RX.

The wired settings are as follows

// LoRa-02 SX1278 module PINs:
// 3.3 V and ground : Connected to 3V3 and GND of Arduino UNO
// RST : Connected to PIN-9 of Arduino UNO
// NSS : Connected to PIN-10 of Arduino UNO
// MOSI : Connected to PIN-11 of Arduino UNO
// MISO : Connected to PIN-12 of Arduino UNO
// SCK : Connected to PIN-13 of Arduino UNO
// DIO0 : : Connected to PIN-2 of Arduino UNO

The connections are same for both RX and TX side.
I am using LoRa Library of Sandeep Mistry version 0.8.0 and used example programs LoRa Sender, which is as below

#include <SPI.h>
#include <LoRa.h>

int counter = 0;

void setup() {
Serial.begin(9600);
while (!Serial);

Serial.println("LoRa Sender");

if (!LoRa.begin(433E6)) {
Serial.println("Starting LoRa failed!");
while (1);
}
}

void loop() {
Serial.print("Sending packet: ");
Serial.println(counter);

// send packet
LoRa.beginPacket();
LoRa.print("hello ");
LoRa.print(counter);
LoRa.endPacket();

counter++;

delay(5000);
}

LoRA Receive:

#include <SPI.h>
#include <LoRa.h>

void setup() {
Serial.begin(9600);
while (!Serial);

Serial.println("LoRa Receiver");

if (!LoRa.begin(433E6)) {
Serial.println("Starting LoRa failed!");
while (1);
}
}

void loop() {
// try to parse packet
int packetSize = LoRa.parsePacket();
if (packetSize) {
// received a packet
Serial.print("Received packet '");

// read packet
while (LoRa.available()) {
  Serial.print((char)LoRa.read());
}

// print RSSI of packet
Serial.print("' with RSSI ");
Serial.println(LoRa.packetRssi());

}
}

Except for the frequency, I have not changed any thing in code.
At the TX side, I see prints "Sending Packet" with counter incrementing
On the TX side, I do not see any packets coming.

Both TX and RX side, it does not say LoRa failed, so, I assume Lora is not failed, but the packets are not seen on RX side.

I do not know if there is issue in TX side or issue in RX side.

The LoRa Module which I use reads on case as

RA-02
ISM: 410-525MHz
PA: +18dBm
LoRa/FSK/00k

2

Suggest you disconnect the LoRa modules from the UNOs as soon as you can.

The LoRa modules are 3.3V logic level and its pins should not be directly connected to a 5V logic level Arduino such as a UNO, they can be damadged.

If you do want to connect the LoRa device to a UNO use logic level conversion connections.

Heaps and heaps easier to use LoRa modules with 3.3V logic Micro controllers or Arduinos.

1 Like
3

Both. Use logic level shifters to connect 5V and 3.3V devices. You may already have damaged one or both components.

4

Thank you. Unfortunately this information is forth coming clearly from demos and videos available on internet. Will try with a new set of components and level shifters.

5

Thank you for the suggestion. Will try with a new set of components and level shifters.

1 Like
6

I recommend the Adafruit Feather LoRa boards. They have advanced 3.3V processors directly connected to the radios, are easy to use and work as advertised.

1 Like
7

I have several of the Adafruit Feather 32u4 LoRa modules used for testing systems - with LoRa onboard removes all the problems with interconnecting wires and resultant intermittent problems
these days tending to move to Heltec WiFi LoRa 32(V3), ESP32S3 + SX1262 LoRa Node
ESP32S3 microcontroller (with onboard WiFi and BLE) + LoRa SX1262 + OLED display

8

Dear All.
The root cause of LoRA module not working when directly connected to Ardiono board is due to difference in IO voltage levels. As suggested in this forum, I have used level convertor to convert 5V IO signal to 3.3V while interfacing with SX1278. The problem got solved.

So, please keep in mind, to always have a level convertor between Arduinoi Uno and Semtech AX1278 LoRA module.

1 Like