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Purpose

The purpose of the Ring-Of-Things is to use the openwsn firmware stack and the CoAP library to implement a simple demo where a 'ringmaster' (in this case a local python client), instructs motes via CoAP packet communication to do simple actions like blink or buzz.

Powerpoint of initial design: https://docs.google.com/presentation/d/1atlBdYjgV6HwVyvTbz42K-ek7jkmLHYt7oatlnUHvk0

Design

A CoAP app must be added to the firmware, called 'rrt', to allow for the ringmaster to send and receive CoAP packets to the resource.  A tutorial for adding a CoAP app is described here: Adding a CoAP app

This app needs to have several functionalities:

  • notify the ringmaster of a mote's availability (when it goes 'online')
  • ability for a mote to wait for an incoming packet from the ringmaster
  • checking for a message type upon reception, and knowing whether to 'blink', 'buzz', perform another simple action, or forward an action to another mote (identified via ipv6)
  • ability to send a CoAP packet from itself to another mote (with some data)

The ringmaster needs to:

  • send packets to motes via the coap library
  • wait on incoming packets
  • keep track of all motes that are in its ring (in this case with a simple queue) and send instructions in a rotation
  • handle error handling - motes dropping off unexpectedly, packet loss, receiving unexpected packets

Code

The firmware code is the main addition, which runs on the motes.

Here is the firmware pull request: https://github.com/openwsn-berkeley/openwsn-fw/pull/128/

List of files changed:

bsp/boards/python/openwsnmodule_obj.h - add rrt_vars_t struct to python OpenMote struct

inc/opendefs.h - add ringmaster port constant on which to listen to and send ring master packets

openapps/SConscript - add rrt as part of the default apps to be built with SCons

openapps/openapps.c - add rrt_init(), the initialization function for rrt resource

openapps/rrt/rrt.c - add rrt resource to openapps, with the code for handling all mote actions.  A GET action sends confirmation to the ringmaster, a POST action accepts payloads and determines what to do next (forward, perform action, or nothing), and a DELETE (which unregisters a mote).  rrt.c also defines a function sendCoAPMsg, which sends a char to either an address or a hardcoded ringmaster address

openapps/rrt/rrt.h - define function signatures to be used outside of rrt.c, as well as the rrt_vars_t struct

openapps/rrt/rrt.py - simple python program for testing python coap library functionality - no purpose

openstack/04-TRAN/opencoap.h - hardcoded ringmaster address added here 

openstack/04-TRAN/openudp.c - add blocks for the ringmaster port in udp receive and send 

openstack/SConscript - add proper path for rrt folder

projects/python/SConscript.env - add proper constants to get the proper objectification




 

 

GitHub repo: https://github.com/openwsn-berkeley/ringmaster

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