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 - firmware
The firmware code is the main addition (openwsn-fw), which runs on the motes.
Here is the firmware pull request: https://github.com/openwsn-berkeley/openwsn-fw/pull/128/
| File Changed | Description |
|---|---|
| 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 other than coap library experimentation |
| openstack/04-TRAN/opencoap.h | hardcoded ringmaster address added here |
| openstack/04-TRAN/openudp.c | add switch blocks for the ringmaster port in openudp_receive and openudp_sendDone |
| openstack/SConscript | add proper path for rrt folder |
| projects/python/SConscript.env | add proper constants to get the proper objectification |
Code - ringmaster.py
Here is the repo: https://github.com/openwsn-berkeley/ringmaster
To run the client, simply execute
python ringmaster.py
This will open up communication with OpenWSN motes on default port 15000.
This script maintains a stack (array) of registered motes that have sent a discovery packet to it. It maintains a pointer which rotates through the stack.