Deep Sleep and OTAA (m328p / LMIC)

bertrik · June 21, 2019, 12:55pm

This Arduino stack allows you to save the session keys (and network id, upload counter):

I’m basing a node on this library for use with an ESP32 TTGO LoRa board where the session keys and some counters are stored in (simulated) EEPROM here. In the EV_JOINED callback, I’m saving them:

github.com

bertrik/LoraWanPmSensor/blob/master/LoraWanPmSensor.ino#L152


    break;
case EV_BEACON_TRACKED:
    Serial.println(F("EV_BEACON_TRACKED"));
    break;
case EV_JOINING:
    Serial.println(F("EV_JOINING"));
    setLoraStatus("OTAA JOIN...");
    break;
case EV_JOINED:
    Serial.println(F("EV_JOINED"));
    LMIC_getSessionKeys(&otaa_data.netid, &otaa_data.devaddr, otaa_data.nwkKey,
                        otaa_data.artKey);
    otaa_data.magic = OTAA_MAGIC;
    EEPROM.put(0, otaa_data);
    EEPROM.commit();


    print_keys();


    setLoraStatus("JOIN OK!");
    break;
case EV_JOIN_FAILED:

Upon startup, I check my EEPROM structure for a previously saved session, and restore it using either LMIC_SetSession(…), or do a JOIN using LMIC_StartJoining():

github.com

bertrik/LoraWanPmSensor/blob/master/LoraWanPmSensor.ino#L304


snprintf(screen.loraDevEui, sizeof(screen.loraDevEui),
         "%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X", deveui[7], deveui[6], deveui[5], deveui[4],
         deveui[3], deveui[2], deveui[1], deveui[0]);


// LMIC init
os_init();
LMIC_reset();
LMIC_setClockError(MAX_CLOCK_ERROR * 1 / 100);
EEPROM.begin(512);
EEPROM.get(0, otaa_data);
if (otaa_data.magic == OTAA_MAGIC) {
    setLoraStatus("Resume OTAA");
    LMIC_setSession(otaa_data.netid, otaa_data.devaddr, otaa_data.nwkKey, otaa_data.artKey);
    print_keys();
} else {
    LMIC_startJoining();
}


char version[32];
if (sds_version(version, sizeof(version))) {
    Serial.print("SDS version and date: ");