Find out about the reason for MQTT and the different messages used.
Reason for MQTT
For communication between different parts in the system MQTT is used. As seen in the Architecture, nealry every part in the system publishes/subscibes to a broker. With this setup, messages in different topics can trigger different reactions. For example, this is used to inform the UI about a new score.
Handy controls
Schwierigkeit: was ist mit den vereinbarten Contracts? MQTT-Topics können nicht einfach ausgetauscht werden, ohne nicht alle zu benachrichtigen, die Zuhören. Aber: Woher weiß ich überhaupt, wer alles auf das Topic lauscht? –> Kommunikation wird entgegen üblicher Annahmen noch viel wichtiger, wenn so wie hier entkoppelt wird
MQTT messages
| topic | Description | Example payload | Comment |
|---|---|---|---|
| leds/backgroundlight/color | Sets the background light, default is #000000 | #CC11DD | |
| ball/position | The ball absolute position on the table, between 0 and 1 | { “x”: 0.5, “y”: 0.3333} | |
| ball/velocity | The balls average speed in the last half second, km/h | { “velocity”: 30 } | deprecated |
| ball/velocity/kmh | The balls average speed in the last half second, km/h | 30 | |
| ball/velocity/ms | The balls average speed in the last half second, m/s | 5 | |
| team/scored | The id of the team that scored | 1 | |
| game/score | The teams’ scores | { “score”: [ 0, 3 ] } | deprecated |
| game/score/<teamid> | Score of team with teamid <teamid> (zero-based) | 3 | |
| game/foul | Some foul has happened | - | |
| game/start | A match starts | - | |
| game/gameover | A match ended | { “winners”: [ 0 ] } | |
| game/idle | Is there action on the table | true | |
| game/reset | Command to interrupt the running game and startover | ||
| leds/foregroundlight/color | Foreground light overrules everything else if not #000000 | #111111 |