Simple Embedded System Project

Objective

Work together as a class to create a wireless network of interactive devices. An example would be one controller responsible for lights, another controller responsible for motion sensor, and a central control can interact with these controllers to perform tasks such as turning on lights when motion has been detected.

Your board contains wireless mesh network allowing you to freely connect many boards together and they can all communicate with each other. You will exploit this capability to do something creative, and ultimately learn, and have fun.

Structure

There are minimum three nodes to be designed by a team of 6; you can add more nodes and more people in a team if you project is challenging enough. Each team is then split into smaller sub-team for the design of each of the nodes. Each team will also compete with the other teams in your class and your grade will be assigned relative to each other with the best team earning the best grade.

Each sub-team of 2 should take ownership of what they will do. You shall not share the code with each other; but instead just list out "how" you can communicate. For example, the owners of the light controller node can list this table to communicate with them :

Wireless Setup
Wireless Channel	2580
Wireless bitrate	250
Wireless Address	110
Command List
Lights ON	Send 1 byte with value 1
Lights OFF lights	Send 2
Lights Auto	Send 3

Example Nodes

The nodes listed below are just examples. You can and should create your own node with its own purpose that goes above and beyond the examples listed in this article. Four unique features are required per node, and some hints are provided in the latter part of this document. Do not worry about the "how"; let the class instructors help you. Just think about the "what".

Lights Node

This node shall act like a wireless node that is responsible to turn on and off lights. This will involve some hardware design such that you can connect your board to some high-power LEDs. Look-up “super bright led” at sparkfun.com for examples.

Sensor Node

This node shall act like a sense point for the commander node. The objective is not just to provide the on-board sense points such as temperature and light, but also implement features such that you can report other creative sense points such as a motion sensor, and distance sensor.

Commander Node

This node shall be responsible to put it all together and serve as a single commanding node to get sensor input and control the lights. This node shall provide the interface for the user, so try to provide user options to configure features such as automatic lights, or remote controlled operation.

Requirements

Technical

• You must use a switch / case code section in your code.
• You must use a state machine in you code.

  This could be as simple as a state machine for "Manual Lights" vs. "Automatic Lights"

• You must utilize functions that use pass-by-value and pass-by-reference.
• Project should be self-contained

  Project should be enclosed, with no wires visible.

  Project should operate either by a battery or USB, but not a computer's USB port.

  Should not require the Hercules Terminal to operate

  All buttons should be labeled.

Deliverables

At the end of the project, the following items need to be submitted :

• Full source-code of all the projects
• Individual evaluations about team members and their contribution

  This will be confidential, and you can submit as one per person (at Canvas).

Project Report

You must submit a full, documented report for your project. The following are minimum sections required in your PDF submitted report:

• Introduction

  What does your project do?

  Try to sell your project in this section.

• Schematics

  List the hardware you used.

  Use "LibreOffice Draw" to draw the schematics

• Implementation

  Show your software workings using a flow-chart

  Use bullets and pictures to show the "how" part.

  Discuss the nodes, and their wireless protocol (table of commands).

• Testing

  What kind of tests did you perform?

  What kind of problems did you solve?

• Conclusion

  What did you learn?

  What worked, and what didn't work?

  How would you improve your project?

Challenges & Hints

Challenges

Over the course of the project, you will encounter some real-world problems such as :

• How will you design your project to be user friendly?
• How will you collaborate in your large team?
• How will you balance your budget and keep parts cost to a minimum?
• How will you design your network protocol such that each team understands a command and response system well?
• How will you make your project more creative? How will it stand out?
• What if you command a light output node that is not responding?

  How will you report this to the user and what would you do?

Hints

Small debugging techniques will help :

• For the commander, implement a "ping" packet that is sent to everyone once a second.

  If an ACK is received, turn on an LED, otherwise turn it off (one LED per remote node).

  This will immediately help diagnose connection issues.

• Any security ?

  What if I get on your network and sabotage your project?

  Can you implement a method such that a command is not so easy for anyone to send?

Sample Code

Light Sensor Node

#include "wireless.h"

void process_command(char command);

int main(void)
{
    char our_addr = 100;
    mesh_set_node_addr(our_addr);

    while (1) {
        /* Check if we get a packet within 1 second : */
        mesh_packet_t wireless_pkt;
        if (wireless_get_rx_pkt(&wireless_pkt, 1000)) {
            /* Assuming first data byte is our command: */
            process_command(pkt.data[0]);
        }
    }
    return 0;
}

void process_command(char command)
{
    enum {
        lights_on = 1;
        lights_off = 2;
    }

    switch(command) {
        case lights_on:
            /* TODO Turn on lights */
        break;

        case lights_off:
            /* TODO Turn off lights */
        break;

        default:
            /* TODO Take action for invalid command */
        break;
    }
}

Commander Node

#include "wireless.h"

int main(void)
{
    /* Same enum as lights controller */
    enum {
        lights_on = 1;
        lights_off = 2;
    }

    char our_addr = 200;
    char lights_addr = 100;
    mesh_set_node_addr(our_addr);

    while (1) {
        /* Turn lights on/off every 3 seconds */
        char cmd = 0;

        cmd = lights_on;
        wireless_send(lights_addr, mesh_pkt_ack, &cmd, 1);
        if (wireless_get_ack_pkt(&pkt, 100)) {
            // We got an acknowledge from lights_addr
        }
        else {
            printf("ERROR: No acknowledge from %i (lights)\n", lights_addr);
        }
        delay_ms(3000);

        cmd = lights_off;
        wireless_send(lights_addr, mesh_pkt_ack, &cmd, 1);
        /* TODO Check if we got an ACK */
        delay_ms(3000);
    }
    return 0;
}