Too many TX

[Beetix]

Describe the bug

The device sends too many uplinks (at a 5s interval) at the beginning of the execution.

Environment

• LMIC: 4.1.1
• PlatformIO Core: 6.1.4
• Network provider: Chipstack
• Region: EU868
• Board : M5Stack Core 2 with LoRa 868 module
• CPU: ESP32
• Radio: SX1276

To Reproduce

plaformio.ini

[env:m5stack-core2]
platform = espressif32
board = m5stack-core2
framework = arduino
lib_deps =
    m5stack/M5Core2@^0.1.2
    mcci-catena/MCCI LoRaWAN LMIC library@^4.1.1
monitor_speed = 115200
build_flags = 
	-D hal_init=LMIC_hal_init
	-D ARDUINO_LMIC_PROJECT_CONFIG_H_SUPPRESS
	-D CFG_eu868
	-D CFG_sx1276_radio=1

main.cpp

/*******************************************************************************
 * Copyright (c) 2015 Thomas Telkamp and Matthijs Kooijman
 * Copyright (c) 2018 Terry Moore, MCCI
 *
 * Permission is hereby granted, free of charge, to anyone
 * obtaining a copy of this document and accompanying files,
 * to do whatever they want with them without any restriction,
 * including, but not limited to, copying, modification and redistribution.
 * NO WARRANTY OF ANY KIND IS PROVIDED.
 *
 * This example sends a valid LoRaWAN packet with payload "Hello,
 * world!", using frequency and encryption settings matching those of
 * the The Things Network.
 *
 * This uses OTAA (Over-the-air activation), where where a DevEUI and
 * application key is configured, which are used in an over-the-air
 * activation procedure where a DevAddr and session keys are
 * assigned/generated for use with all further communication.
 *
 * Note: LoRaWAN per sub-band duty-cycle limitation is enforced (1% in
 * g1, 0.1% in g2), but not the TTN fair usage policy (which is probably
 * violated by this sketch when left running for longer)!

 * To use this sketch, first register your application and device with
 * the things network, to set or generate an AppEUI, DevEUI and AppKey.
 * Multiple devices can use the same AppEUI, but each device has its own
 * DevEUI and AppKey.
 *
 * Do not forget to define the radio type correctly in
 * arduino-lmic/project_config/lmic_project_config.h or from your BOARDS.txt.
 *
 *******************************************************************************/
#include <M5Core2.h>
#include <lmic.h>
#include <hal/hal.h>
#include <SPI.h>

// This EUI must be in little-endian format, so least-significant-byte
// first. When copying an EUI from ttnctl output, this means to reverse
// the bytes. For TTN issued EUIs the last bytes should be 0xD5, 0xB3,
// 0x70.
static const u1_t PROGMEM APPEUI[8]={ 0 };
void os_getArtEui (u1_t* buf) { memcpy_P(buf, APPEUI, 8);}

// This should also be in little endian format, see above.
static const u1_t PROGMEM DEVEUI[8]={ 0x00, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01 };
void os_getDevEui (u1_t* buf) { memcpy_P(buf, DEVEUI, 8);}

// This key should be in big endian format (or, since it is not really a
// number but a block of memory, endianness does not really apply). In
// practice, a key taken from ttnctl can be copied as-is.
static const u1_t PROGMEM APPKEY[16] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x00 };
void os_getDevKey (u1_t* buf) {  memcpy_P(buf, APPKEY, 16);}

static uint8_t mydata[] = "Hello M5LoRaKit!";
static osjob_t sendjob;

// Schedule TX every this many seconds (might become longer due to duty
// cycle limitations).
const unsigned TX_INTERVAL = 60;

// Pin mapping
// https://docs.m5stack.com/en/module/lora868
const lmic_pinmap lmic_pins = {
  .nss = 33,                       
  .rxtx = LMIC_UNUSED_PIN,
  .rst = 26,                       
  .dio = {36, 35, LMIC_UNUSED_PIN}, 
};

void printHex2(unsigned v) {
    v &= 0xff;
    if (v < 16)
        Serial.print('0');
    Serial.print(v, HEX);
}

void do_send(osjob_t* j){
    // Check if there is not a current TX/RX job running
    if (LMIC.opmode & OP_TXRXPEND) {
        Serial.println(F("OP_TXRXPEND, not sending"));
    } else {
        // Prepare upstream data transmission at the next possible time.
        LMIC_setTxData2(1, mydata, sizeof(mydata)-1, 0);
        Serial.println(F("Packet queued"));
    }
    // Next TX is scheduled after TX_COMPLETE event.
}

void onEvent (ev_t ev) {
    Serial.print(os_getTime());
    Serial.print(": ");
    switch(ev) {
        case EV_SCAN_TIMEOUT:
            Serial.println(F("EV_SCAN_TIMEOUT"));
            break;
        case EV_BEACON_FOUND:
            Serial.println(F("EV_BEACON_FOUND"));
            break;
        case EV_BEACON_MISSED:
            Serial.println(F("EV_BEACON_MISSED"));
            break;
        case EV_BEACON_TRACKED:
            Serial.println(F("EV_BEACON_TRACKED"));
            break;
        case EV_JOINING:
            Serial.println(F("EV_JOINING"));
            break;
        case EV_JOINED:
            Serial.println(F("EV_JOINED"));
            {
              u4_t netid = 0;
              devaddr_t devaddr = 0;
              u1_t nwkKey[16];
              u1_t artKey[16];
              LMIC_getSessionKeys(&netid, &devaddr, nwkKey, artKey);
              Serial.print("netid: ");
              Serial.println(netid, DEC);
              Serial.print("devaddr: ");
              Serial.println(devaddr, HEX);
              Serial.print("AppSKey: ");
              for (size_t i=0; i<sizeof(artKey); ++i) {
                if (i != 0)
                  Serial.print("-");
                printHex2(artKey[i]);
              }
              Serial.println("");
              Serial.print("NwkSKey: ");
              for (size_t i=0; i<sizeof(nwkKey); ++i) {
                      if (i != 0)
                              Serial.print("-");
                      printHex2(nwkKey[i]);
              }
              Serial.println();
            }
            // Disable link check validation (automatically enabled
            // during join, but because slow data rates change max TX
	    // size, we don't use it in this example.
            LMIC_setLinkCheckMode(0);
            break;
        /*
        || This event is defined but not used in the code. No
        || point in wasting codespace on it.
        ||
        || case EV_RFU1:
        ||     Serial.println(F("EV_RFU1"));
        ||     break;
        */
        case EV_JOIN_FAILED:
            Serial.println(F("EV_JOIN_FAILED"));
            break;
        case EV_REJOIN_FAILED:
            Serial.println(F("EV_REJOIN_FAILED"));
            break;
        case EV_TXCOMPLETE:
            Serial.println(F("EV_TXCOMPLETE (includes waiting for RX windows)"));
            if (LMIC.txrxFlags & TXRX_ACK)
              Serial.println(F("Received ack"));
            if (LMIC.dataLen) {
              Serial.print(F("Received "));
              Serial.print(LMIC.dataLen);
              Serial.println(F(" bytes of payload"));
            }
            Serial.print(F("Next transmission = "));
            Serial.println(os_getTime()+sec2osticks(TX_INTERVAL));
            // Schedule next transmission
            os_setTimedCallback(&sendjob, os_getTime()+sec2osticks(TX_INTERVAL), do_send);
            break;
        case EV_LOST_TSYNC:
            Serial.println(F("EV_LOST_TSYNC"));
            break;
        case EV_RESET:
            Serial.println(F("EV_RESET"));
            break;
        case EV_RXCOMPLETE:
            // data received in ping slot
            Serial.println(F("EV_RXCOMPLETE"));
            break;
        case EV_LINK_DEAD:
            Serial.println(F("EV_LINK_DEAD"));
            break;
        case EV_LINK_ALIVE:
            Serial.println(F("EV_LINK_ALIVE"));
            break;
        /*
        || This event is defined but not used in the code. No
        || point in wasting codespace on it.
        ||
        || case EV_SCAN_FOUND:
        ||    Serial.println(F("EV_SCAN_FOUND"));
        ||    break;
        */
        case EV_TXSTART:
            Serial.println(F("EV_TXSTART"));
            break;
        case EV_TXCANCELED:
            Serial.println(F("EV_TXCANCELED"));
            break;
        case EV_RXSTART:
            /* do not print anything -- it wrecks timing */
            break;
        case EV_JOIN_TXCOMPLETE:
            Serial.println(F("EV_JOIN_TXCOMPLETE: no JoinAccept"));
            break;

        default:
            Serial.print(F("Unknown event: "));
            Serial.println((unsigned) ev);
            break;
    }
}

void setup() {
    M5.begin();

    // LMIC init
    os_init();
    // Reset the MAC state. Session and pending data transfers will be discarded.
    LMIC_reset();

    // Start job (sending automatically starts OTAA too)
    do_send(&sendjob);
}

void loop() {
    os_runloop_once();
}

Expected behavior

Single uplink every minute.

Serial output

Packet queued
105935: EV_JOINING
295678: EV_TXSTART
615440: EV_JOINED
netid: 0
devaddr: 9B643E
AppSKey: 3B-C6-8B-E6-5B-FF-17-CD-04-59-65-C4-FA-52-DD-2D
NwkSKey: 15-6F-CA-81-C8-AA-45-3F-10-82-1E-D2-1A-5F-DD-1E
616191: EV_TXSTART
686273: EV_TXCOMPLETE (includes waiting for RX windows)
Next transmission = 4436280
1033155: EV_TXSTART
1101937: EV_TXCOMPLETE (includes waiting for RX windows)
Next transmission = 4851943
1322132: EV_TXSTART
1390914: EV_TXCOMPLETE (includes waiting for RX windows)
Next transmission = 5140921
1611107: EV_TXSTART
1679890: EV_TXCOMPLETE (includes waiting for RX windows)
Next transmission = 5429896
1900083: EV_TXSTART
2042310: EV_TXCOMPLETE (includes waiting for RX windows)
Next transmission = 5792316
5792338: EV_TXSTART
Packet queued
5935853: EV_TXCOMPLETE (includes waiting for RX windows)
Next transmission = 9685859

[terrillmoore]

Sorry you're having problems.

I think you'll find that chirpstack is sending MAC messages to your device that require response. Each uplink from the device causes another downlink from Chirpstack, until Chirpstack has finished sending the MAC messages. I don't believe this is a bug in the LMIC, but rather known behavior with Chirpstack.

[Beetix]

I see! Thank you.

I will investigate on Chirpstack to confirm this behavior.

[cyberman54]

I can confirm this, saw the same on a chirpstack network. The TX's are initiated by MAC commands from the network.

[kadirozdinc]

I have a same problem with lmic library but when I use arduino-lorawan library instead of arduino-lmic library, I did not encounter this to many tx problem. What should we edit/add in this library to sort the problem out ?

[Andermutu]

I found a solution, you have to disable MAC commands on chirpstack:

Mac-commands disabled.

mac_commands_disabled=true