arduino-LoRa: Guru meditation error while using onTxDone /onReceive on ESP32

Thank you so much @Jose2059 for your detailed response. After reading it, I’ve spend some hours to go deeper, working arround your approach.

@GIPdA GIPdA, thank you too, “merci beaucoup même”, I kept your quote in mind during my tests: I suspect there’s a function somewhere that sometimes waits too long.

The last night, I’ve found data I asked to send when I tried to read, it is another thing to know.

So! I’ve have something which seems to work, even in bad conditions and making send and receive using interrupts without any crash.

In some words:

Declare a volatile flag, initialize lora, create a xTask for reading and configure the interrupt to set the flag to true, only that. In the xTask, make a loop with a read only if the flag is true then set it to false. It is the solution given by @Jose2059 and it works for pure receiving.

But if you want to send too, be careful and take in consideration the flag! If you try to send something when it is true, you will make something bad in a buffer and when the task will try to read, the Guru crash may appears.

In this code, I tried to reproduce real conditions, enabling Wifi, sending and a periodic long process. There is no crash.

I just noticed after some minutes (over 10), the receive may stops to work. But it is another problem I will try to resolve.

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

#define PIN_SCK 18
#define PIN_MISO 19
#define PIN_MOSI 23
#define PIN_SS 5
#define PIN_RST 26
#define PIN_DI0 36
#define FREQUENCY 433E6

volatile bool _receivedLoRaP{false};

unsigned long _sendingPacketNumber = 0;
unsigned long _sendingTimer = 0;
unsigned long _processTimer = 0;

void setup() {

    delay(1000);

    // -------------------------------------------------------------------
    // Initialize Serial, Wire (I2C) and SPI

    Serial.begin(115200);

    // Make it heavier, turn on Wifi
    WiFi.softAP("WIFI_HOTSPOT_SSID", "WIFI_HOTSPOT_PASS");


    SPI.begin(PIN_SCK, PIN_MISO, PIN_MOSI);

    LoRa.setPins(PIN_SS, PIN_RST, PIN_DI0);

    if(!LoRa.begin(FREQUENCY)) {
        Serial.println("Failed to start LoRa");
        while (true);
    }

    Serial.println("LoRa started");

    xTaskCreatePinnedToCore(
        core0Task,              // Function that should be called
        "core0Task",            // Name of the task (for debugging)
        5000,                   // Stack size (bytes)
        NULL,                   // Parameter to pass
        3,                      // Task priority                                    <--- increased to 3
        NULL,                   // Task handle
        1                       // Core you want to run the task on (0 or 1)        <-- seems work better on core 1
    );
}

void loop() {

    delay(100);

    // ----------------------------------------------------------------------------------------------
    // TICKET FOR THE GURU MEDITATION ERROR: SEND WHILE A PACKET IS AVAILABLE
    if (millis() - _sendingTimer > 5000) {

        // THE LIFE SAVER: MAKE THE SENDING LATER
        if (_receivedLoRaP)
            return;

        Serial.print("Sending packet ");
        Serial.println(_sendingPacketNumber);

        // Send a realistic packet
        LoRa.beginPacket();
        LoRa.print("1 77777777 ");
        LoRa.print(_sendingPacketNumber++);
        LoRa.print(" 704 0 0 {\"state\":{\"time\":3639083,\"type\":\"ground module\",\"battery\":25,\"ram\":0}}");
        LoRa.endPacket();

        // Back to receive mode (required for the next interrupt)
        LoRa.receive();

        // Rearm timer
        _sendingTimer = millis();
    }
    // ---------------------------------------------------------------------------------------------


    // ----------------------------------------------------------------------------------------------
    // LET's MAKE IT HARDER WITH A PERIODIC LONG PROCESS IN LOOP
    if (millis() - _processTimer > 3000) {

        Serial.print("Emulating a long process");

        for (uint16_t i = 0; i < 500; i++)
            Serial.print(".");

        Serial.println("");

        // Rearm timer
        _processTimer = millis();
    }
}

void loRaOnReceiveInterrupt(int packetLength) {
    _receivedLoRaP = true;
}

void core0Task(void * parameter) {

    // Looks better to define it here (instead of setup)
    LoRa.onReceive(loRaOnReceiveInterrupt);
    LoRa.receive();

    while(true) {

        if (_receivedLoRaP) {

            // LoRa.sleep(); //< why? ----------------------------------------

            Serial.print("RX: ");
            Serial.println(LoRa.readString());

            _receivedLoRaP = false;
            // LoRa.receive();
        }

        vTaskDelay(10);
    }
}

The trace looks to this, with other module sending packet each 5 seconds:

RX: 1 77777777 167 704 0 0 {"state":{"time":3639083,"type":"ground module","battery":25,"ram":0}}
Sending packet 132
Emulating a long process........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................      
Emulating a long process........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................      
RX: 1 77777777 168 704 0 0 {"state":{"time":3639083,"type":"ground module","battery":25,"ram":0}}
Sending packet 133
Emulating a long process........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................      
RX: 1 77777777 169 704 0 0 {"state":{"time":3639083,"type":"ground module","battery":25,"ram":0}}
Emulating a long process........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................      
Sending packet 134
Emulating a long process........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................      
RX: 1 77777777 170 704 0 0 {"state":{"time":3639083,"type":"ground module","battery":25,"ram":0}}
Sending packet 135
Emulating a long process..........