meshquitto

A simple Arduino project, which aims to provide a gateway between a mesh network of ESP8266's and a remote MQTT broker.

How it works

• The mesh network is created by making use of the amazing painlessMesh library (see here).
• The Meshquitto gateway is composed of 2 ESP8266 devices (tested on D1-mini).
  • The first of the two devices (MQTT gateway) connects to an available WiFi network and consequently establishes a connection to a MQTT broker. Any messages received from the MQTT broker are forwarded to the Mesh gateway and vice versa.
  • The second (Mesh gateway) connects to the mesh network. Any messages received from the MQTT gateway are forwarded to the Mesh network and vice versa.
  • Since Software serial does not provide parity check functionality, CRC16 (see here for library) is used to detect transmission errors. (NOTE: Retransmition is not currently implemented, thus corrupted messages are simply dropped).
• The topic structure of messages is shown in the image above:
  • <MQTT_gateway_subtopics> form the first (few) subtopic(s) of the MQTT topic, which are used solely for subscription and publishing identification of the gateway with the MQTT broker.
  • Each of the mesh nodes (including the Mesh gateway) then are abstracted from the <MQTT_gateway_subtopics> and simply "publish" and "subscribe" to the <Mesh_network_subtopics>.
  • Removal and concatenation of the <MQTT_gateway_subtopics> is handled by the MQTT gateway.
• AES encryption (see relevant library here) has been imported in order to add an extra security layer to messages passed between nodes in the mesh.