Lab 28. Backbone mode

Owned by Thomas Watteyne
Last updated: Apr 05, 2017
1 min read

Expected completion time of this lab: 40 min.

The latency with the default settings is on the order of 1 second per hop. While this allows for excellent power consumption, for some applications, this is too slow. In this part, we will explore the range of achievable latencies, by using the LEDPing sample application.

The  LEDPing application interacts with a mote in master mode, using OAP. It sends a command to set the LED on, waits for an indication that the change was done, sends a command to set the LED off, etc.

Without backbone mode

  • Start the LEDPing application, and connect to the manager.
  •  Enter the MAC address of the mote in the text field, then press start. 

  • Using a stopwatch, what is the time it takes for the LED to switch ON 10 times?  

    Answer 28.1:


     

  • What is the average RTT of the network (round-trip time)?

    Answer 28.2:


With backbone mode

"Backbone" is a mode where all cells of the communication schedule are scheduled. This yields very low latencies, at the cost of an increased power consumption.

  • On the manager’s CLI, enter:

    > login user
> show config

  • What is the value of bbmode parameter?

    Answer 28.3:


  • Enter the following commands:

    > set config bbmode 2
> set config bbsize 2

  • Power cycle both the manager and the mote. Wait for the mote to join.

  • Repeat the measurements above. What is the RTT now?

    Answer 28.4: