MQTT specifications

Hi Team,

I have a system with R2 release software with 1 gateway and 1 proxy via the Raspberry PI Board. The proxy sends to my MQTT Server. Everything seems to be working properly. I need to know how MQTT messages are actually handled. When is the CONFIG message sent? I noticed that sometimes I get sent back and not just to the start. When is the STATUS message sent from the tags and with which event? Is it completely managed by the gateway? I noticed that, even if the tag is on, sometimes I get “status false”. I used that event to remove or to display the tag on my map, but often having “status true / false status” I have display problems. Can you send me a documentation or a report on how MQTT communication is managed and on which events in a precise way?


Hi Luca,

here is a list of uplink topics (from the UWB network to the MQTT Broker):

{prefix}/node/{deviceId}/uplink/config - last known configuration (MQPP.retain = true). Whenever an edge-node changes its configuration a new message is published.

{prefix}/node/{deviceId}/uplink/status last known status - online/offline status (MQPP.retain = true). Whenever an edge-node changes its state a new message is published (QoS is 1).

{prefix}/node/{deviceId}/uplink/location - last known location (MQPP.retain = true). Whenever an edge-node reports a new location a new message is published (QoS is 0).

{prefix}/node/{deviceId}/uplink/data - user data (MQPP.retain = false). Whenever an edge-node sends new data (QoS is 0) a new message is published (QoS is 0).

{prefix}/gateway/{deviceId}/uplink - information about the bridge node or proxy (contains IP address of the Daemon/Proxy, network ID, … QoS is 1). Whenever the bridge/proxy changes configuration a new message is published.

Note: in MQTT retain flag means the message will be stored on the MQTT Broker until it is cleared by someone. The broker stores only one retained message per topic here always the last published retained message is stored. As soon as a MQTT client connects to the Broker it will send all retained messages of topics to which the client subscribes to.


1 Like

Hi team,

Thanks for the reply.

I had noticed the retain flag and it is very useful, especially as an initial map setting.

Other questions:

  • ‘{prefix}/node/{deviceId}/uplink/config’ and ‘{prefix}/node/{deviceId}/uplink/status’ are sent whenever an edge-node changes its configuration/state and when the node is turned on?
    I’ve noticed that I get config messages without changes from time to time. Is it possible that the node reboots in some way? If yes, can you list the cases? (does any watchdog come into play?).

  • I noticed a TX power difference between the new and old DWM1001 modules, is that correct? In some cases, the new modules fail to send their data to the gateway. I have seen that through the command ‘dwm_uwb_cfg_set’ it is possible to set the TX Power, but they are 4 bytes. What do these 4 bytes represent? Is it possible to set the power as in the old modules?