Can't join OTAA RFM95; seeing different frequencies and SF for RX


Hi All,

I tried to use ABP to send message to TTN and i got the payload, but since i try to use OTAA, i can’t join, at TTN console gateway i got message join accept but in node side, the log said EV_JOIN_FAILED. After check debug output at my node rfm95 i found odd output where the TX send data using x frequency but RX using y frequency as example log output below:

66429753: EV_JOIN_FAILED
66429758: engineUpdate, opmode=0xc
67349743: engineUpdate, opmode=0xc
67351971: TXMODE, freq=914300000, len=23, SF=10, BW=125, CR=4/5, IH=0
67671843: RXMODE_SINGLE, freq=925700000, SF=10, BW=500, CR=4/5, IH=0
67704521: RXMODE_SINGLE, freq=923300000, SF=12, BW=500, CR=4/5, IH=0
67835100: engineUpdate, opmode=0xc
67846746: engineUpdate, opmode=0xc
67848965: TXMODE, freq=909400000, len=23, SF=8, BW=500, CR=4/5, IH=0
68163918: RXMODE_SINGLE, freq=925700000, SF=7, BW=500, CR=4/5, IH=0
68168276: RXMODE_SINGLE, freq=923300000, SF=12, BW=500, CR=4/5, IH=0
68298866: EV_JOIN_FAILED

So i think that’s why node print EV_JOIN_FAILED didn’t accept message join approval from TTN due to difference frequency.

And added information, my gateway with the node pretty near, only 1-2 meters

Here a video record i took while troubleshoot this issue,

(Arjan) #2

Why would you expect the same frequencies? For RX1 that’s indeed to be expected for some regions, like EU868, but looking at that looks okay for US902-928 and AU915-928.

However, the difference in SF might we weirder, but I am not familiar with these regions:

So, in which region are you? And what library are you using, with what settings?

Also, I don’t see the 914.3 nor 909.4 on that page, though you’re seeing the OTAA Join in TTN Console, so maybe I don’t understand that page, or it’s not up to date. See also

Maybe a search for LMIC_setClockError and hybrid mode will help.

(And always keep at least a few meters between node and gateway. I’ve not looked at your video, but we surely need more details to be able to help.)


Hi @arjanvanb thanks to give some hint, what i mean TX using x freq and RX using y freq is while the node tried to join to WAN, node will give some information to gateway at freq X (for example X at 914.3MHz) then after information sent to TTN and it accept the key then TTN sent back information through gateway that node can join to the network and sent back to node in freq 914.3MHz but unfortunately the RX node using 925.7MHz so the information didn’t receive by node. That’s what i understand about join OTAA cmiiw.

My region in Indonesia so i set the gateway freq 923MHz, i use Global Config Korean Region because it use 923MHz too.

I use library LMIC 1.5 from github

My node use wemos D1mini.

Why you need to see 914.3 or 909.4?

I put value from 1 to 20 at LMIC_setClockError after LMIC_reset but nothing changed, maybe i will try for hybrid mode.

Sorry can’t quote your question due to use mobile phone while reply.


Fadli Mukhtarif

(Arjan) #4

Because they are listed in your own logging:

But apparently the packet is received, so apparently the node and gateway agree on that these frequencies are available. However:

Hmmm, states:

Indonesia AS923-925 (“AS2”)

South Korea KR920-923

So, while I still don’t know the details about those regions, why not make the nodes use AS923-925, for which 914.3 or 909.4 are NOT listed as supported uplink frequencies, and make sure that you’ve selected the good region for the gateway too?

(Jreiss) #5

The arduino-lmic library referenced only supports US915 or EU868.

To use with KR920 the EU868 code will be closer in functionality but the frequencies would need to be modified to match the KR920 default frequencies and allowed ranges. Duty-cycle code could be disabled. KR920 also requires LBT which is not implemented in lmic


Hi All, Thanks the hint, seems what @arjanvanb and @jreiss is make sense, library from @matthijskooijman only support 915Mhz and 868MHz, so i will try to research maybe someone has custom library for 923MHz.

What i thought before was library 915MHz can covered 923MHz too, my bad :grimacing: i’ll let give further information if i need more help. Thanks all



Lucky, MCCI has custom LMIC provide AS_923, i can joined OTAA now, but now i have another problem which is each time the node sent data, the gateway is not forward data except at SF 10 (based on TTN gateway console), here the screenshot i took, the counter missing some number. 33

Maybe someone now what’s going on?

(Jreiss) #8

Looks like you are only receiving on the default frequencies.
Perhaps there is a mismatch between the frequencies in the Join Accept CFList and what the gateway is configured for.

(Arjan) #9

Am I right to understand that at SF7, 8 and 9 you don’t receive anything at all, and at SF10 you’re missing some packets?

If so, then @jreiss already answered about the problems at SF10.

Regarding SF7, 8 and 9: the higher the SF, the longer the airtime and the better the reception/maximum distance. So, to use a lower (better) SF you need to be improve the reception. Like be closer to the gateway, put your gateway and/or node in a higher position, and so on. See Best position for a gateway.