Unsolicited downlinks

Question

How to avoid unwanted down link with null port and null frm_payload ?
Some of my sensor receive unconfirmedDataDown with port value as null, and frm_payload value as null too without I send something. I would like to know why, understand if I have done something wrong and how to control this if it's possible.Here are two examples of different sensors brought up by different gateways.
unconfirmedDataDown_with-port-null_with-payload-null_15-57.png

Orne Brocaar · Answer

The first / left downlink contains a mac-command to re-synchronize the channel configuration. Normally within EU868 these channels are sent as part of the CFList in the join-accept, but if a device sends an uplink with adr_ack_req: true, ChirpStack will re-negotate these channels with the device.

THe second / right downlink contains an ack: true, most likely because the preceeding uplink was a confirmed uplink, and thus must be acknowledged by ChirpStack.

Unsolicited downlinks

1 Answers