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HaMQTT Protocol

(Discussion Document)

An MQTT Interface to an Amateur Radio Station

The proposed (now functional) device is apiece of ESP8266-based hardware, which sits between a Ham radio and an MQTT broker. The Ham radio receives Dual Tone Multimple Frequency (DTMF) sequences and relays them back to and MQTT broker. The hardware, then transmits any subscribed MQTT messages. The length of teh incoming DTMF sequence is 8 characters or less. This is a nominal value seelcted due to two assumptions:

  • There is no enter key so input must be by timeout, which must be short or it becomes a pain in the ass.
  • If the user is entering the charaters by hand, more than 8 charaters is a pain in the ass to type.

The protocol allows Commands and Queries. Essentially, we send contents to (Command) or request contents from (Query) virtual memory locations. Certain sequences are reserved. Commands Start with * Queries Start with #

commands / Queries for the DTMF / MQTT Dialog Engine Hardware

*7 or #7 is a command or query to the engine. That's the actual ESP8266 hardware itself.

  • *700 close the relay. After this, further DTMF sequences are not forwarded to the MQTT broker.
  • *701 open the engine. After this, all DTMF sequences are forwarded to the MQTT broker.
  • *710nnnn set the auto-close timeout (nnnn=seconds)
  • *711nnnn set the input timeout (nnnn=seconds)

Long Commands / Queries

  • *8 long command
  • *9 data for a long command
  • #8 long query
  • #9 RESERVED