# Arduino LMIC: cannot receive downlink messages

**URL:** <https://www.thethingsnetwork.org/forum/t/arduino-lmic-cannot-receive-downlink-messages/15956>\
**Category:** LMIC\
**Created:** [July 16, 2018, 12:32pm UTC](https://www.thethingsnetwork.org/forum/t/arduino-lmic-cannot-receive-downlink-messages/15956 "2018-07-16T12:32:12Z")\
**Posts on this page:** 1\
**Showing post:** 34

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**Author:** ![arjanvanb](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/arjanvanb/32/46626_2.png) [@arjanvanb](https://www.thethingsnetwork.org/forum/u/arjanvanb)\
**Post date:** [July 19, 2018, 6:41pm UTC](https://www.thethingsnetwork.org/forum/t/arduino-lmic-cannot-receive-downlink-messages/15956/34 "2018-07-19T18:41:52Z")

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> [@Memeos135](#):
>
> TTN frequency plan shown in the link you provided me displays 8 channels for uplink, each channel corresponding to a downlink as well (903.9 –\> 923.3… 904.1 –\> 923.9… etc).

But for the uplink [it specifies](https://www.thethingsnetwork.org/docs/lorawan/frequency-plans.html#us902-928) SF7 to SF10, while for the downlinks it lists SF7 to SF12. Also, the uplinks have 9 frequencies, the downlinks only 8, so I can only assume that 904.6 SF8 should not be used when relying on downlinks, like when using ADR? Not a clear specification if you’d ask me. Also, US has the notion of [“hybrid”](https://www.thethingsnetwork.org/forum/search?q=hybrid) which is not mentioned at all?

> [@BerndWOB](#):
>
> It seems that the gateway then stores the message and transmits it after the next uplink message was sent.

If that’s true, then I’d not alter my application/node but I’d look for a different test gateway, or get a full gateway.

But indeed, if the downlink has not already been scheduled then TTN might not wait long enough for the application to return a downlink. But then TTN is scheduling it for the next opportunity, not the gateway; see [My application's downlink is always queued for next uplink](https://www.thethingsnetwork.org/forum/t/my-applications-downlink-is-always-queued-for-next-uplink/7014).

([This ESP8266 test gateway](https://github.com/JaapBraam/LoRaWanGateway) worked great for me, for EU868. See also @bluejedi’s list in [Single Channel Packet Forwarder part 3 [Deprecated]](https://www.thethingsnetwork.org/forum/t/single-channel-gateway-part-3/11546) .)

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