Add mqtt topic documentation.

Author: brocaar

docs/topics.md

@@ -0,0 +1,81 @@
+# MQTT topics
+
+To receive data from your gateways, you need to subscribe to its MQTT topic(s).
+For debugging, you can use a (command-line) tool like ``mosquitto_sub``
+which is part of the [Mosquitto](http://mosquitto.org/) MQTT broker.
+
+Use ``+`` for a single-level wildcard, ``#`` for a multi-level wildcard.
+Examples:
+
+```bash
+mosquitto_sub -t "gateway/#" -v                   # show data from all gateways
+mosquitto_sub -t "gateway/0101010101010101/+" -v  # show all data for the given gateway
+```
+
+## gateway/[MAC]/stats
+
+Topic for gateway statistics. Example payload:
+
+```json
+{
+    "altitude": 0,
+    "latitude": 0,
+    "longitude": 0,
+    "mac": "1dee08d0b691d149",
+    "rxPacketsReceived": 2,
+    "rxPacketsReceivedOK": 1,
+    "time": "2016-06-10T14:04:53Z"
+}
+```
+
+## gateway/[MAC]/rx
+
+Topic for received packets (from nodes). Example payload:
+
+```json
+{
+    "phyPayload": "AAEBAQEBAQEBAgICAgICAgJpNbxrAh8=",  // base64 encoded LoRaWAN packet
+    "rxInfo": {
+        "channel": 1,
+        "codeRate": "4/5",
+        "crcStatus": 1,
+        "dataRate": {
+            "bandwidth": 125,
+            "modulation": "LORA",
+            "spreadFactor": 7
+        },
+        "frequency": 868300000,
+        "loRaSNR": 7,
+        "mac": "1dee08d0b691d149",
+        "rfChain": 1,
+        "rssi": -57,
+        "size": 23,
+        "time": "0001-01-01T00:00:00Z",
+        "timestamp": 2074240683                        // gateway internal timestamp (32 bit) with microsecond precision
+    }
+}
+```
+
+## gateway/[MAC]/tx
+
+Topic for publishing packets to be transmitted by the given gateway.
+Example payload:
+
+```json
+{
+    "phyPayload": "IKu70cumKom7BREUFrxlHtM=",
+    "txInfo": {
+        "codeRate": "4/5",
+        "dataRate": {
+            "bandwidth": 125,
+            "modulation": "LORA",
+            "spreadFactor": 7
+        },
+        "frequency": 868300000,
+        "immediately": false,
+        "mac": "1dee08d0b691d149",
+        "power": 14,
+        "timestamp": 2079240683
+    }
+}
+```

mkdocs.yml

@@ -2,6 +2,7 @@ site_name: LoRa Semtech Bridge documentation
 pages:
   - index.md
   - getting-started.md
+  - topics.md
   - changelog.md
 theme: readthedocs
 repo_url: https://github.com/brocaar/lora-semtech-bridge/