OTAA activation and downlink payload #91

acsaba1977 · 2025-07-05T09:58:27Z

acsaba1977
Jul 5, 2025

Hi everyone,
I have just a curiosity regarding the OTAA. I'm using ChirpStack network server and I'm trying to send downlink messages to the node.
It looks the downlink message is not the one that I'm sending. For example, I send a message like: Data HEX - d2 04 d9 fd 3d 42 54 52 98 41 f5 e2 68 68 00 00 00 00 14 00 and I'm receiving 7B B5 DD 77 4E 35 80 E5 B2 29 2F FE FE F1 40 A6 54 C6 85 A5 (Always changing).
For the OTAA, the mandatory values should be AppKey, EUID and Join EUI. In the initialization phase, I'm also asked for the Network Key which is mandatory. The uplink (From the node to the network server) the communication works well and the message is correct. Only the downlink is altered.
I'm using:
Library:

#include <heltec_unofficial.h>
#include <LoRaWAN_ESP32.h>

PlatformIO configuration.

[env:heltec_wifi_lora_32_V3]
platform = espressif32
board = heltec_wifi_lora_32_V3
framework = arduino
upload_port = /dev/ttyUSB0
monitor_speed = 115200
lib_deps = 
	ropg/Heltec_ESP32_LoRa_v3@^0.9.2
	ropg/LoRaWAN_ESP32@^1.2.0

Any hint on what I'm doing wrong?

The data link looks fine:
Downlink data length: 20
Downlink port: 30, confirmed: 1, frmPending: 1, datarate: 5, freq: 867.299988, power: 2, fCnt: 3, multicast: 0
In the rmPending: 1 is always the same message: (d2 04 d9 fd 3d 42 54 52 98 41 f5 e2 68 68 00 00 00 00 14 00) and it is consumed.

Relevant code:

  uint8_t downlinkData[20];
  size_t lenDown = sizeof(downlinkData);
 LoRaWANEvent_t downlEvent;
 LoRaWANEvent_t uploadEvent;

state = node->sendReceive((uint8_t *) & myRegistrationPayload.payload, sizeof(myRegistrationPayload.payload), REGISTATION_UPLINK_PORT, downlinkData, &lenDown, false,  &uploadEvent, &downlEvent);



  if(state == RADIOLIB_ERR_NONE) {
    Serial.println("Message sent, no downlink received.");
  } else if (state > 0) {
    Serial.println("Message sent, downlink received.");

    Serial.printf("Downlink data length: %zu\n", lenDown);
    Serial.printf("Downlink port: %u, confirmed: %u, frmPending: %u, datarate: %u, freq: %f, power: %d, fCnt: %u, multicast: %u\n",
                  downlEvent.fPort, downlEvent.confirmed ? 1:0, downlEvent.frmPending ? 1:0, downlEvent.datarate, downlEvent.freq, downlEvent.power, downlEvent.fCnt, downlEvent.multicast ? 1:0);
 
    Serial.printf("Downlink RAW data: ");
    for (size_t i = 0; i < lenDown; ++i) {
      Serial.printf("%02X ", downlinkData[i]);
    }
    Serial.println();

  } else {
    Serial.printf("sendReceive returned error %d, we'll try again later.\n", state);
  }

Many thanks for your support.

Answered by StevenCellist

Jul 9, 2025

Right.. the big problem is that you must have configured that the device (profile) supports Class B, but RadioLib does not support Class B which is definitely mentioned all over the place 😉
Subsequently, Chirpstack sends the MAC command to set the Class B ping slots to 0 MHz (not used), which is an unknown command since RadioLib does not support it.
The fix will be to disable the support for Class B.

View full answer

StevenCellist · 2025-07-08T14:35:14Z

StevenCellist
Jul 8, 2025

As there is no other reply, I'll add the comment that you probably pulled down RadioLib 7.2 as a dependency while installing this library. There is a bug in RadioLib 7.2 that results in downlink payload being decoded incorrectly when there is some MAC payload in the downlink as well. In the first few downlinks after joining, there is usually MAC payload for ADR for instance. So the decoding bug plays up.
Please confirm if you have RadioLib 7.2 installed in your dependencies folder (I think the version is set in RadioLib's BuildOpt.h at the bottom). We'll likely soon bump to 7.2.1 to get the patch out for this bug.

16 replies

acsaba1977 Jul 9, 2025
Author

The version is LoraWAN 1.1 and the NwkKey is fine. I have checked several times. The uplink and join just works well.

Using node.setClass(RADIOLIB_LORAWAN_CLASS_C); and node.getDownlinkClassC(downlinkPayload, &downlinkLen, &downlinkEvent); the payload looks OK.
Using node.setClass(RADIOLIB_LORAWAN_CLASS_A); and node.sendReceive(uplinkPayload, sizeof(uplinkPayload),2, downlinkPayload, &downlinkLen, &uplinkEvent, &downlinkEvent); the downlonk payload dose not look OK.

Many thanks and really sorry bothering you.

StevenCellist Jul 9, 2025

No worries man, I wouldn't go out of my way to comment on someone else's repo if it had bothered me. And please have a sleep before reading on ;)

The reason why Class C works, is that Class C downlinks are not allowed to carry MAC commands and subsequently don't fall into the Unknown MAC CID. Apparently, there is some issue decoding some MAC payload that is carried in the normal (Class A) downlinks.

I am not completely sure what the root cause of this would be, especially if all the keys are correct.
If you are comfortable with it, can you please share the DevEUI, JoinEUI, AppKey and NwkKey of your setup, and show a complete log of JoinRequest + JoinAccept + Uplink + Downlink? Very preferably just one log instance, not separate log parts.
Also, please provide the info of the downlink you schedule, just as the screenshot before (FPort + Payload). Please then also include the JSON of the downlink as provided by the Chirpstack logs.

With that info I can run a full decode of the packets and see what parts decode correctly and what parts don't, and possibly other unexpected stuff that occurs.

If you are concerned about the security of the keys, feel free to change them right after. The EUIs are transmitted plainly with the JoinRequest, so no loss of security sharing those.

acsaba1977 Jul 9, 2025
Author

Nothing secret :) It is just a playground.

Application key and Network key (Both are the same): ad35cbce17c155adb2f66f78574664f1

#define RADIOLIB_LORAWAN_JOIN_EUI  0x0000000000000000

// the Device EUI & two keys can be generated on the TTN console 
#ifndef RADIOLIB_LORAWAN_DEV_EUI   // Replace with your Device EUI
#define RADIOLIB_LORAWAN_DEV_EUI   0x5ee930b186c1d3a3
#endif
#ifndef RADIOLIB_LORAWAN_APP_KEY   // Replace with your App Key 
#define RADIOLIB_LORAWAN_APP_KEY   0xad, 0x35, 0xcb, 0xce, 0x17, 0xc1, 0x55, 0xad, 0xb2, 0xf6, 0x6f, 0x78, 0x57, 0x46, 0x64, 0xf1
#endif
#ifndef RADIOLIB_LORAWAN_NWK_KEY   // Put your Nwk Key here
#define RADIOLIB_LORAWAN_NWK_KEY   0xad, 0x35, 0xcb, 0xce, 0x17, 0xc1, 0x55, 0xad, 0xb2, 0xf6, 0x6f, 0x78, 0x57, 0x46, 0x64, 0xf1
#endif

Console Debug

Setup ... 
Initialise the radio
Join ('login') the LoRaWAN Network
[5.170898] RLB_PRO: UL:   0 1 868.100 (0 - 5) | DL:   0 1 868.100 (0 - 5)
[5.171403] RLB_PRO: UL:   1 1 868.300 (0 - 5) | DL:   1 1 868.300 (0 - 5)
[5.181849] RLB_PRO: UL:   2 1 868.500 (0 - 5) | DL:   2 1 868.500 (0 - 5)
[5.192268] RLB_PRO: [MAC] 0x03
[5.192385] RLB_PRO: 00000000: 30                                               0                 
[5.202694] RLB_PRO: LinkAdrReq: dataRate = 3, txSteps = 0, nbTrans = 0
[5.202977] RLB_PRO: LinkAdrAns: 07
[5.203071] RLB_PRO: [MAC] 0x04
[5.213362] RLB_PRO: 00000000: 07                                               .                 
[5.223687] RLB_PRO: DutyCycleReq: max duty cycle = 1/2^7
[5.223739] RLB_PRO: [MAC] 0x05
[5.223813] RLB_PRO: 00000000: 00 d2 ad 84                                      ....              
[5.234140] RLB_PRO: RXParamSetupReq: Rx1DrOffset = 0, rx2DataRate = 0, freq = 869.525
[5.251709] RLB_PRO: [MAC] 0x08
[5.251857] RLB_PRO: 00000000: 01                                               .                 
[5.251963] RLB_PRO: RXTimingSetupReq: delay = 1 sec
[5.262210] RLB_PRO: [MAC] 0x09
[5.262279] RLB_PRO: 00000000: 05                                               .                 
[5.272558] RLB_PRO: [MAC] 0x0c
[5.272610] RLB_PRO: 00000000: 65                                               e                 
[5.282881] RLB_PRO: ADRParamSetupReq: limitExp = 6, delayExp = 5
[5.293191] RLB_PRO: [MAC] 0x0f
[5.293247] RLB_PRO: 00000000: fa                                               .                 
[5.303542] RLB_PRO: RejoinParamSetupReq: maxTime = 15, maxCount = 10
[5.372034] RLB_PRO: JoinRequest (DevNonce = 0):
[5.372268] RLB_PRO: 00000000: 00 00 00 00 00 00 00 00 00 a3 d3 c1 86 b1 30 e9  ..............0.
[5.382692] RLB_PRO: 00000010: 5e 00 00 78 93 3c ad                             ^..x.<.           
[5.383186] RLB_PRO: 
[5.393454] RLB_PRO: PHY:  Frequency = 868.100 MHz, TX = 16 dBm
[5.394990] RLB_PRO: LoRa: SF = 9, BW = 125.0 kHz, CR = 4/5, IQ: U
[5.618614] RLB_PRO: Uplink sent <-- Rx Delay start
[5.619114] RLB_PRO: 
[5.619167] RLB_PRO: PHY:  Frequency = 868.100 MHz, TX = 16 dBm
[5.630902] RLB_PRO: LoRa: SF = 9, BW = 125.0 kHz, CR = 4/5, IQ: D
[10.612865] RLB_PRO: Opened Rx1 window (115 ms timeout)... <-- Rx Delay end 
[10.725653] RLB_PRO: Closing Rx1 window
[10.869720] RLB_PRO: JoinAccept (JoinNonce = 114, previously 0):
[10.869993] RLB_PRO: 00000000: 20 72 00 00 00 00 00 e9 ad cb 01 80 01 18 4f 84   r............O.
[10.880433] RLB_PRO: 00000010: e8 56 84 b8 5e 84 88 66 84 58 6e 84 00 dd 87 92  .V..^..f.Xn.....
[10.890750] RLB_PRO: 00000020: 6e                                               n                 
[10.890840] RLB_PRO: LoRaWAN revision: 1.1
[10.902501] RLB_PRO: [MAC] 0x05
[10.902598] RLB_PRO: 00000000: 00 d2 ad 84                                      ....              
[10.912877] RLB_PRO: RXParamSetupReq: Rx1DrOffset = 0, rx2DataRate = 0, freq = 869.525
[10.913665] RLB_PRO: [MAC] 0x08
[10.924017] RLB_PRO: 00000000: 01                                               .                 
[10.934311] RLB_PRO: RXTimingSetupReq: delay = 1 sec
[10.934375] RLB_PRO: Processing CFList
[10.934419] RLB_PRO: [MAC] 0x07
[10.944745] RLB_PRO: 00000000: 03 18 4f 84 50                                   ..O.P             
[10.945229] RLB_PRO: UL:   3 1 867.100 (0 - 5) | DL:   3 1 867.100 (0 - 5)
[10.955745] RLB_PRO: [MAC] 0x07
[10.955860] RLB_PRO: 00000000: 04 e8 56 84 50                                   ..V.P             
[10.966599] RLB_PRO: UL:   4 1 867.300 (0 - 5) | DL:   4 1 867.300 (0 - 5)
[10.977100] RLB_PRO: [MAC] 0x07
[10.977229] RLB_PRO: 00000000: 05 b8 5e 84 50                                   ..^.P             
[10.987937] RLB_PRO: UL:   5 1 867.500 (0 - 5) | DL:   5 1 867.500 (0 - 5)
[10.988294] RLB_PRO: [MAC] 0x07
[10.998577] RLB_PRO: 00000000: 06 88 66 84 50                                   ..f.P             
[10.999112] RLB_PRO: UL:   6 1 867.700 (0 - 5) | DL:   6 1 867.700 (0 - 5)
[11.009657] RLB_PRO: [MAC] 0x07
[11.009771] RLB_PRO: 00000000: 07 58 6e 84 50                                   .Xn.P             
[11.020521] RLB_PRO: UL:   7 1 867.900 (0 - 5) | DL:   7 1 867.900 (0 - 5)
Sending a confirmed uplink
[11.032344] RLB_PRO: Uplink MAC payload:
[11.032491] RLB_PRO: 00000000: 0b 01 20 00                                      .. .              
[11.111038] RLB_PRO: Uplink (FCntUp = 0) decoded:
[11.111265] RLB_PRO: 00000000: 5b 31 31 2e 30 32 30 35 32 31 5d 20 52 4c 42 5f  [11.020521] RLB_
[11.121654] RLB_PRO: 00000010: 80 e9 ad cb 01 84 00 00 a1 c3 67 b9 01 db 20 38  ..........g... 8
[11.121769] RLB_PRO: 00000020: 36 37                                            67                
[11.134141] RLB_PRO: 
[11.134240] RLB_PRO: PHY:  Frequency = 867.700 MHz, TX = 16 dBm
[11.146044] RLB_PRO: LoRa: SF = 9, BW = 125.0 kHz, CR = 4/5, IQ: U
[11.338996] RLB_PRO: Uplink sent <-- Rx Delay start
[11.339481] RLB_PRO: 
[11.339534] RLB_PRO: PHY:  Frequency = 867.700 MHz, TX = 16 dBm
[11.351253] RLB_PRO: LoRa: SF = 9, BW = 125.0 kHz, CR = 4/5, IQ: D
[12.332874] RLB_PRO: Opened Rx1 window (115 ms timeout)... <-- Rx Delay end 
[12.445655] RLB_PRO: Closing Rx1 window
[14.534389] RLB_PRO: Downlink (NFCntDown = 0) encoded:
[14.534674] RLB_PRO: 00000000: 49 00 00 00 00 01 e9 ad cb 01 00 00 00 00 00 17  I...............
[14.545115] RLB_PRO: 00000010: 60 e9 ad cb 01 af 00 00 c4 3b fc 34 d5 56 e6 7b  `........;.4.V.{
[14.545283] RLB_PRO: 00000020: 41 3e f5 f0 c7 e6 8c 26 42 c9 f2                 A>.....&B..       
[14.555941] RLB_PRO: [MAC] 0x0b
[14.566174] RLB_PRO: 00000000: 01                                               .                 
[14.566266] RLB_PRO: RekeyConf: server version = 1.1
[14.576575] RLB_PRO: [MAC] 0x20
[14.576632] RLB_PRO: 00000000: 00                                               .                 
[14.586922] RLB_PRO: DeviceMode: Switching to LoRaWAN Class A
[14.597174] RLB_PRO: [MAC] 0x03
[14.597308] RLB_PRO: 00000000: 53 ff 00 00 00 00 00 00 00 00 00 00 00 01        S.............    
[14.607577] RLB_PRO: LinkAdrReq: dataRate = 5, txSteps = 3, nbTrans = 1
[14.607689] RLB_PRO: UL:   0 1 868.100 (0 - 5) | DL:   0 1 868.100 (0 - 5)
[14.618250] RLB_PRO: UL:   1 1 868.300 (0 - 5) | DL:   1 1 868.300 (0 - 5)
[14.618444] RLB_PRO: UL:   2 1 868.500 (0 - 5) | DL:   2 1 868.500 (0 - 5)
[14.628834] RLB_PRO: UL:   3 1 867.100 (0 - 5) | DL:   3 1 867.100 (0 - 5)
[14.639249] RLB_PRO: UL:   4 1 867.300 (0 - 5) | DL:   4 1 867.300 (0 - 5)
[14.639431] RLB_PRO: UL:   5 1 867.500 (0 - 5) | DL:   5 1 867.500 (0 - 5)
[14.649838] RLB_PRO: UL:   6 1 867.700 (0 - 5) | DL:   6 1 867.700 (0 - 5)
[14.660253] RLB_PRO: UL:   7 1 867.900 (0 - 5) | DL:   7 1 867.900 (0 - 5)
[14.660640] RLB_PRO: LinkAdrAns: 07
[14.670942] RLB_PRO: [MAC] 0x06
[14.671143] RLB_PRO: DevStatusAns: status = 0xff0b
[14.671197] RLB_PRO: WARNING: Unknown MAC CID 11
[14.681422] RLB_PRO: WARNING: Skipping remaining MAC payload
[14.681911] RLB_PRO: 
[14.681984] RLB_PRO: PHY:  Frequency = 867.700 MHz, TX = 10 dBm
[14.693691] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: U
Ready!

Sending uplink
[30.136065] RLB_PRO: Uplink MAC payload:
[30.136248] RLB_PRO: 00000000: 03 07 06 ff 0b                                   .....             
[30.215040] RLB_PRO: Uplink (FCntUp = 1) decoded:
[30.215279] RLB_PRO: 00000000: 1d 08 e5 00 00 78 56 ad 04 ce ce 3f 17 00 00 00  .....xV....?....
[30.225657] RLB_PRO: 00000010: 80 e9 ad cb 01 85 01 00 e3 a3 e0 a4 ae 02 e5 06  ................
[30.225785] RLB_PRO: 00000020: 97 ce ce 3f f7                                   ...?.             
[30.238665] RLB_PRO: 
[30.238759] RLB_PRO: PHY:  Frequency = 868.500 MHz, TX = 10 dBm
[30.250491] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: U
[30.314685] RLB_PRO: Uplink sent <-- Rx Delay start
[30.315169] RLB_PRO: 
[30.315216] RLB_PRO: PHY:  Frequency = 868.500 MHz, TX = 10 dBm
[30.326958] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: D
[31.309862] RLB_PRO: Opened Rx1 window (37 ms timeout)... <-- Rx Delay end 
[31.344653] RLB_PRO: Closing Rx1 window
[33.522390] RLB_PRO: Downlink (AFCntDown = 0) encoded:
[33.522677] RLB_PRO: 00000000: 49 01 00 00 00 01 e9 ad cb 01 00 00 00 00 00 15  I...............
[33.533123] RLB_PRO: 00000010: 60 e9 ad cb 01 aa 00 00 b2 42 df b6 26 c1 31 b1  `........B..&.1.
[33.533278] RLB_PRO: 00000020: b2 99 14 79 ff 4a 2b 0f b9                       ...y.J+..         
[33.543891] RLB_PRO: [MAC] 0x03
[33.554257] RLB_PRO: 00000000: 54 ff 00 00 00 00 00 00 00 00 00 00 00 01        T.............    
[33.554349] RLB_PRO: LinkAdrReq: dataRate = 5, txSteps = 4, nbTrans = 1
[33.564698] RLB_PRO: UL:   0 1 868.100 (0 - 5) | DL:   0 1 868.100 (0 - 5)
[33.575266] RLB_PRO: UL:   1 1 868.300 (0 - 5) | DL:   1 1 868.300 (0 - 5)
[33.575471] RLB_PRO: UL:   2 1 868.500 (0 - 5) | DL:   2 1 868.500 (0 - 5)
[33.585851] RLB_PRO: UL:   3 1 867.100 (0 - 5) | DL:   3 1 867.100 (0 - 5)
[33.596265] RLB_PRO: UL:   4 1 867.300 (0 - 5) | DL:   4 1 867.300 (0 - 5)
[33.596458] RLB_PRO: UL:   5 1 867.500 (0 - 5) | DL:   5 1 867.500 (0 - 5)
[33.606855] RLB_PRO: UL:   6 1 867.700 (0 - 5) | DL:   6 1 867.700 (0 - 5)
[33.607049] RLB_PRO: UL:   7 1 867.900 (0 - 5) | DL:   7 1 867.900 (0 - 5)
[33.617666] RLB_PRO: LinkAdrAns: 07
[33.617775] RLB_PRO: WARNING: Unknown MAC CID 11
[33.628025] RLB_PRO: WARNING: Skipping remaining MAC payload
[33.628488] RLB_PRO: 
[33.628547] RLB_PRO: PHY:  Frequency = 868.500 MHz, TX = 8 dBm
[33.640194] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: U
State : 1
Received a downlink
Downlink data: 59 4C 
Downlink length: 2
[LoRaWAN] Frame count:  2
Sending uplink
[63.787062] RLB_PRO: Uplink MAC payload:
[63.787268] RLB_PRO: 00000000: 03 07                                            ..                
[63.866037] RLB_PRO: Uplink (FCntUp = 2) decoded:
[63.866243] RLB_PRO: 00000000: 1d 08 e5 00 00 78 56 ad 04 ce ce 3f 17 00 00 00  .....xV....?....
[63.876625] RLB_PRO: 00000010: 80 e9 ad cb 01 82 02 00 01 6a 02 67 96 82 56 ad  .........j.g..V.
[63.876744] RLB_PRO: 00000020: 04 ce                                            ..                
[63.889115] RLB_PRO: 
[63.889220] RLB_PRO: PHY:  Frequency = 867.500 MHz, TX = 8 dBm
[63.900948] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: U
[63.959995] RLB_PRO: Uplink sent <-- Rx Delay start
[63.960491] RLB_PRO: 
[63.960535] RLB_PRO: PHY:  Frequency = 867.500 MHz, TX = 8 dBm
[63.972268] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: D
[64.953869] RLB_PRO: Opened Rx1 window (37 ms timeout)... <-- Rx Delay end 
[64.988653] RLB_PRO: Closing Rx1 window
[66.122373] RLB_PRO: Downlink (NFCntDown = 1) encoded:
[66.122661] RLB_PRO: 00000000: 49 02 00 00 00 01 e9 ad cb 01 01 00 00 00 00 12  I...............
[66.133109] RLB_PRO: 00000010: 60 e9 ad cb 01 aa 01 00 7f 17 14 70 3a 99 c4 ff  `..........p:...
[66.133249] RLB_PRO: 00000020: 3e 6a ed a8 db 2d                                >j...-            
[66.143877] RLB_PRO: [MAC] 0x03
[66.154245] RLB_PRO: 00000000: 55 ff 00 00 00 00 00 00 00 00 00 00 00 01        U.............    
[66.154341] RLB_PRO: LinkAdrReq: dataRate = 5, txSteps = 5, nbTrans = 1
[66.164684] RLB_PRO: UL:   0 1 868.100 (0 - 5) | DL:   0 1 868.100 (0 - 5)
[66.175253] RLB_PRO: UL:   1 1 868.300 (0 - 5) | DL:   1 1 868.300 (0 - 5)
[66.175454] RLB_PRO: UL:   2 1 868.500 (0 - 5) | DL:   2 1 868.500 (0 - 5)
[66.185840] RLB_PRO: UL:   3 1 867.100 (0 - 5) | DL:   3 1 867.100 (0 - 5)
[66.196252] RLB_PRO: UL:   4 1 867.300 (0 - 5) | DL:   4 1 867.300 (0 - 5)
[66.196440] RLB_PRO: UL:   5 1 867.500 (0 - 5) | DL:   5 1 867.500 (0 - 5)
[66.206844] RLB_PRO: UL:   6 1 867.700 (0 - 5) | DL:   6 1 867.700 (0 - 5)
[66.207040] RLB_PRO: UL:   7 1 867.900 (0 - 5) | DL:   7 1 867.900 (0 - 5)
[66.217654] RLB_PRO: LinkAdrAns: 07
[66.217762] RLB_PRO: WARNING: Unknown MAC CID 11
[66.228012] RLB_PRO: WARNING: Skipping remaining MAC payload
[66.228477] RLB_PRO: 
[66.228538] RLB_PRO: PHY:  Frequency = 867.500 MHz, TX = 6 dBm
[66.240184] RLB_PRO: LoRa: SF = 7, BW = 125.0 kHz, CR = 4/5, IQ: U
State : 1
Received a downlink
Downlink data: 
Downlink length: 0
[LoRaWAN] Frame count:  3

log_ok.json

Hope it helps.

Keep in touch.

StevenCellist Jul 9, 2025

Right.. the big problem is that you must have configured that the device (profile) supports Class B, but RadioLib does not support Class B which is definitely mentioned all over the place 😉
Subsequently, Chirpstack sends the MAC command to set the Class B ping slots to 0 MHz (not used), which is an unknown command since RadioLib does not support it.
The fix will be to disable the support for Class B.

Answer selected by acsaba1977

acsaba1977 Jul 10, 2025
Author

Thank you so much for your help with my issue. I really appreciate your support and explanations.

It turns out that the problem was enabling CLASS_B support in ChirpStack, while the library I’m using — ropg/heltec_esp32_lora_v3 — is based on RadioLib, which doesn’t support CLASS_B devices. I had missed that detail. :(

Thanks again for helping me figure it out!

StevenCellist Jul 10, 2025

You're welcome :)

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OTAA activation and downlink payload #91

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OTAA activation and downlink payload #91

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acsaba1977 Jul 5, 2025

Replies: 1 comment · 16 replies

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