Possible to have LoRa AND 3G communication with RadioHead?

Hey guys,

I’m currently using the RadioHead library with a LoRa shield stacked on a 3G shield (stacked on the arduino, obviously). Now, I can get each shield working separately but when I make a sketch to get data over LoRa and then send it over 3G to ThingSpeak, it does not work. It is either I initialize the 3G shield second and the LoRa shield does not communicate with the client, or I initialize the LoRa shield second and the 3G shield disconnects from the network. Does anyone have any ideas? I have tried changing my program, looking into the library, but RadioHead is pretty complicated and I don’t see where it may be getting in the way. My code:


#include <SoftwareSerial.h>
#include <SPI.h>

#include "Adafruit_FONA.h"
#include "RHReliableDatagram.h"
#include "RH_RF95.h"


#define FONA_TX 4
#define FONA_RX 5
#define FONA_RST 9


uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];

/*----------------------3G CONSTRUCTORS-------------------------*/

SoftwareSerial fonaSS = SoftwareSerial(FONA_TX,FONA_RX);
SoftwareSerial *fonaSerial = &fonaSS;

Adafruit_FONA_3G fona = Adafruit_FONA_3G(FONA_RST);

/*---------------------LORA CONSTRUCTORS------------------------*/

RH_RF95 driver;

RHReliableDatagram LORAmanager(driver, SERVER_ADDRESS);


void setup() {


    if (!LORAmanager.init()){
        Serial.println("init failed");
    } else {
        Serial.println("init succeeded");


void FONAsetup() {
    int i;
    Serial.println(F("FONA basic test"));

    if (! fona.begin(*fonaSerial)) {
        Serial.println(F("Couldn't find FONA"));
        while (1);

    Serial.println(F("FONA is OK"));




    for(i=0;i<3 && !fona.sendCheckReply(F("AT+CHTTPSSTART"), F("OK"), 10000);i++);

void FONASendHTTP() {
    int i=0;
    char getstr[100] = {0};
    char getstr1[] = "GET /update?api_key=2TQ3N7QCJFJXF7KM&field2=";
    char getstr2[] = " HTTP/1.1\r\nHost: api.thingspeak.com\r\n\r\n";

    strcat(getstr, getstr1);
    strcat(getstr, (char*)buf);
    strcat(getstr, getstr2);
    for(i=0;i<3 && !fona.sendCheckReply(F("AT+CHTTPSOPSE=\"api.thingspeak.com\",443,2"), F("OK") ,10000);i++);
    for(i=0;i<3 && !fona.sendCheckReply(F("AT+CHTTPSSEND=120"),F(">"), 10000);i++);
    for(i=0;i<3 && !fona.sendCheckReply(getstr, F("OK"), 10000);i++);
    for(i=0;i<3 && !fona.sendCheckReply(F("AT+CHTTPSCLSE"),F("OK"),10000);i++);

void loop() {
    Serial.println("Check if LoRa received");
    if(LORAmanager.available()) {
            uint8_t len = sizeof(buf);
            uint8_t from;
            if (LORAmanager.recvfromAck(buf, &len, &from))
                Serial.print("Got data: ");
                Serial.println("Intiating HTTP request: ");


The RadioHead library depends on the interrupts to be handled within a short time frame. Using SoftwareSerial for the FONA makes this impossible. Sending one byte using that library blocks the complete CPU for more than 2ms. This cannot work. Use the hardware serial interface for the serial connection.

Pylon, thank you for your response! I ended up putting a time delay before making the HTTP request and after receiving the packet from the LoRa node. This seems to have fixed the problem, but do you know if this is just an unreliable fix?

This seems to have fixed the problem, but do you know if this is just an unreliable fix?

That depends on how often and defined the values on the radio side arrive. If you can ensure that no radio communication happens while the Arduino is sending values to the FONA it might work reliably. If you can't ensure that it might fail any time.