Team Beats by dRAY:

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Published December 4, 2021

Rush Hour

Broken traffic light system at a four-way intersection? We have the fix for you!

IntermediateFull instructions provided72

Things used in this project

Hardware components

Texas Instruments EK-TM4C123GXL TM4C Tiva LaunchPad

Breadboard (generic)

LED, Red

LED, Green

LED, Yellow

Resistor 10k ohm

Tilt Switch, SPST

Software apps and online services

Texas Instruments Code Composer Studio

Story

Introduction

Hello! We are team Beats by dRAY! We have recently gotten our first client, who happens to be an incredibly intelligent and accomplished professor at Rice University. It is none other than Dr. Ray Simar! Unfortunately, a four-way intersection by Dr. Simar's residence has had all of its traffic lights go out, making him late to class one day. As the city of Houston is not known for its speedy road repairs, Dr. Simar has employed us to create a working model of the traffic light system for this four-way intersection, so that he can give this model to the workers and speed along the repairs. He also wants to make his neighborhood safer by incorporating an emergency system that, when activated, turns all the lights red and stops all traffic.

Luckily, we have learned exactly how to do this in our ELEC 220 class this semester! And just in case this has happened to one of your favorite professors as well, we have documented everything needed for this model to be recreated perfectly.

How it Works

In this model traffic light system, each breadboard serves as the traffic light for one direction of traffic, for a total of four directions. The lights work on a timing system, where two opposing "traffic lights" each stay red for a certain amount of time, while the other two stay green. A couple of seconds before the red lights switch to green, the green lights switch to yellow for a short time. Then as the yellow lights switch to red, the red lights switch to green, and the cycle repeats. There is also an emergency system where, if the tilt switch is activated, all the lights turn red, stopping all traffic.

The Build

The circuit for this project may look complicated, with its large assortment of multicolored wires, but no need to fear! This project is only one circuit copied onto four different breadboards, all connected to one launchpad.

First, in order to recreate this model, you'll need a few things:

Tiva C Series TM4C123G
Breadboard x4
Red LED x4
Green LED x4
Yellow LED x4
10k Ohm Resistor x12
Tilt Switch x1
and lots of wires! (30 to be exact)

Now that you have everything you need, time to put it together.

1. Build one breadboard

First, you should build one of the four total breadboards. To do so, place the red light with the short leg in hole f6, the yellow light with the short leg in hole f15, and the green light with the short leg in hole f25. Next you should place the 10k ohm resistors by each light. These should have one leg in a hole in the same row as the long leg of the light, and the other leg in a hole five rows up the column. Then for each light-resistor combo, you should connect one wire from the leg of the resistor not directly next to the light to a port on the launchpad (port C7 for red, port C6 for yellow, and port C5 for green). You should then connect another wire for each light-resistor combo going from the short leg of the light to ground (the negative column). Finally, you will want to connect one wire going from ground to port GND.

one of the four breadboards

2. Build the other three

Now that you have one breadboard, you should copy this same system three times for a total of four breadboards. However, you will only need to connect two of them to a ground port on the launchpad. Connect the other two using a wire going from the ground column on the breadboard to the ground column on a breadboard that is grounded to the launchpad.

all four breadboards attached to launchpad

3. Add the tilt switch

Finally, after all four breadboards are set up, the last step is adding the tilt switch. You should add the tilt switch into holes a1 and a7 on one of the breadboards. Then, add wires going from each of the legs of the tilt switch to ports D7 and 3.3V.

tilt switch added

The Software

The code for this project was done using Code Composer Studio. It initializes ports A, C, and D on the launchpad using the helper function and a pin for each one of the lights. Then, in a while loop, 1 is added to a variable count for every loop, and, through if and else conditions evaluating count, it turns certain lights on and off. There is a copy of our code below.

The Result

And that's it! Now we have a working model of a traffic light system for a four-way intersection! Below is a video of the finished model.

Code

Traffic System Software

HELPERS.H FUNCTION:

/*
 * helpers.h
 *
 *  Created on: Mar 15, 2018
 *      Author: Chance Tarver
 */

#ifndef HELPERS_H_
#define HELPERS_H_


// Base addresses of each port
#define PortA       0x40004000
#define PortB       0x40058000
#define PortC       0x40006000
#define PortD       0x40007000
#define PortE       0x40024000
#define PortF       0x40025000

//  General-Purpose Input/Output Run Mode Clock Gating Control. Each bit corresponds to a Port.
#define RCGCGPIO    0x400FE608
#define ClocksA     0x01
#define ClocksB     0x02
#define ClocksC     0x04
#define ClocksD     0x08
#define ClocksE     0x10
#define ClocksF     0x20

// Define the bitmask for each pin
#define pin0     0x01
#define pin1     0x02
#define pin2     0x04
#define pin3     0x08
#define pin4     0x10
#define pin5     0x20
#define pin6     0x40
#define pin7     0x80

//Other defines for code readability
#define OUTPUT  1
#define INPUT   0
#define INTERRUPT    1
#define NoINTERRUPT  0

// Offsets corresponding to registers we may need to configure
#define GPIODATA    0x3FC   // pg662 : GPIO Data
#define GPIODIR     0x400   // pg663 : GPIO Direction
#define GPIOIS      0x404   // pg664 : GPIO Interrupt Sense
#define GPIOIBE     0x408   // pg665 : GPIO Interrupt Both Edges
#define GPIOIEV     0x40C   // pg666 : GPIO Interrupt Event     -   0: falling edge or Low level is trigger.    1: rising edge or High level is trigger
#define GPIOIM      0x410    // pg667 : GPIO Interrupt Mask      -   0: the pin is masked.                       1: the interrupt is sent to the controller
#define GPIOICR     0x41C    // pg670 : GPIO Interrupt Clear     -   0: no affect                                1: the corresponding interrupt is cleared
#define GPIOAFSEL   0x420   // pg671 : GPIO Alternative Function Select - 0: pin functions as GPIO              1: Function as something else depending on port
#define GPIOPUR     0x510   // pg677 : GPIO Pull-Up Select      -   0: turn off pull up resistor                1: turn on pull up for corresponding pin
#define GPIOPDR     0x514   // pg679 : GPIO Pull-Down Select    -   0: turn off pull down resistor              1: turn on pull down for corresponding pin
#define GPIODEN     0x51C   // pg682 : GPIO Digital Enable      -   0: disable digital functions                1: enable pin's digital functions
#define GPIOLOCK    0x520   // pg684 : GPIO Lock. A write of the value 0x4C4F.434B unlocks the GPIO Commit (GPIOCR) register for write access.
#define GPIOKEY     0x4C4F434B // pg684. Special key for the GPIOLOCK register
#define GPIOCR      0x524   // pg685 : GPIO Commit              -   0: Corresponding GPIOAFSEL, GPIOPUR, GPIOPDR, or GPIODEN bits cannot be written. 1: They can

#define NVIC_EN0_R              (*((volatile unsigned long *)0xE000E100))  // pg142 IRQ 0 to 31 Set Enable Register

#define NVIC_PRI0_R             (*((volatile unsigned long *)0xE000E41C))  // pg152 IRQ 0 to 3 Priority Register
#define NVIC_PRI7_R             (*((volatile unsigned long *)0xE000E41C))  // pg152 IRQ 28 to 31 Priority Register  pg 104 has interrupt assignments. GPIO Port F is Interrupt #30. Bits 23:21

void WaitForInterrupt(void);  // low power mode

void SetupDigitalGPIO(unsigned int port, unsigned int pinMask, int direction,
                        int useInterrupts)
{
    /*Function for setting up a digital GPIO Pin

     This function will do all the register configs for a give port and pin.

     Examples
     -------
     SetupOnDigitalGPIO(PortF, pin3, INPUT, INTERRUPT) // Set up an input with interrupts on PF3.
     SetupOnDigitalGPIO(PortE, pin4, OUTPUT, NoINTERRUPT) // Set up an output with no interrupts on PE4.
     Notes
     -----
     We assume a pullup resistor.
     We also assume an edge based trigger.
     It is best the header with the #defines for each port and pin are included.

     Inputs
     ------
     (*((volatile unsigned long *) port  - Base address of the port being used.
     (*((volatile unsigned long *) pin   - Bit mask of the pin being used
     int direction - Boolean flag for direction of the pin. 1 = Output. 0 = input
     int UseInterrupts - Boolean flag to use interrupts. 1 = use them. 0 = don't
     */

    //Define the generic pointers
    unsigned int volatile *pRCGCGPIO = (unsigned int *) RCGCGPIO;
    unsigned int volatile *pGPIOLOCK = (unsigned int *) (port + GPIOLOCK);
    unsigned int volatile *pGPIOCR = (unsigned int *) (port + GPIOCR);
    unsigned int volatile *pGPIODIR = (unsigned int *) (port + GPIODIR);
    unsigned int volatile *pGPIOAFSEL = (unsigned int *) (port + GPIOAFSEL);
    unsigned int volatile *pGPIOPUR = (unsigned int *) (port + GPIOPUR);
    unsigned int volatile *pGPIODEN = (unsigned int *) (port + GPIODEN);
    unsigned int volatile *pGPIODATA = (unsigned int *) (port + GPIODATA);

    // Define the pointers for interrupt configuration
    unsigned int volatile *pGPIOIS = (unsigned int *) (port + GPIOIS);
    unsigned int volatile *pGPIOIBE = (unsigned int *) (port + GPIOIBE);
    unsigned int volatile *pGPIOIEV = (unsigned int *) (port + GPIOIEV);
    unsigned int volatile *pGPIOIM = (unsigned int *) (port + GPIOIM);
    unsigned int volatile *pGPIOICR = (unsigned int *) (port + GPIOICR);

    // activate the clocks for the port
    int clocks;
    switch ((int) port)
    {
    case PortA:
        clocks = ClocksA;
        break;
    case PortB:
        clocks = ClocksB;
        break;
    case PortC:
        clocks = ClocksC;
        break;
    case PortD:
        clocks = ClocksD;
        break;
    case PortE:
        clocks = ClocksE;
        break;
    case PortF:
        clocks = ClocksF;
        break;
    default:
        clocks = ClocksF;
        break;//ERROR. TODO: Add an exception to handle this. Send to Error ISR or something
    }

    *pRCGCGPIO |= clocks;
    while ((*pRCGCGPIO & clocks) == 0)
        ;

    *pGPIOLOCK = GPIOKEY;
    *pGPIOCR |= pinMask;
    if (direction == 0)
    {
        *pGPIODIR &= ~pinMask;
        *pGPIOPUR |= pinMask;
    }
    else if (direction == 1)
    {
        *pGPIODIR |= pinMask;
    }
    else
    {
        *pGPIODIR |= pinMask; // TODO. Addd an exception to handle this.
    }

    *pGPIOAFSEL &= ~pinMask;
    *pGPIODEN |= pinMask;

    if (useInterrupts)
    {
        *pGPIOIS &= ~pinMask;  // Edge-sensitive (default setting)
        *pGPIOIBE &= ~pinMask;  // Not both edges (default setting)
        *pGPIOIEV &= ~pinMask;  // Falling edge event (default setting)
        *pGPIOICR |= pinMask;   // clear flag
        *pGPIOIM |= pinMask;   // enable interrupt. Unmask it
    }
}


void WaitForInterrupt(void)
{
    __asm ("    WFI\n"
            "    BX     LR\n");
}


#endif /* HELPERS_H_ */


#include "helpers.h"

int main(void)
{
    //Switch
    SetupDigitalGPIO(PortD, pin7, INPUT, NoINTERRUPT);
    //North pins
    //Red
    SetupDigitalGPIO(PortC, pin7, OUTPUT, NoINTERRUPT);
    //Yellow
    SetupDigitalGPIO(PortC, pin6, OUTPUT, NoINTERRUPT);
    //Green
    SetupDigitalGPIO(PortC, pin5, OUTPUT, NoINTERRUPT);

    //South pins
    //Red
    SetupDigitalGPIO(PortA, pin5, OUTPUT, NoINTERRUPT);
    //Yellow
    SetupDigitalGPIO(PortA, pin6, OUTPUT, NoINTERRUPT);
    //Green
    SetupDigitalGPIO(PortA, pin7, OUTPUT, NoINTERRUPT);

    //West pins
    //Red
    SetupDigitalGPIO(PortA, pin4, OUTPUT, NoINTERRUPT);
    //Yellow
    SetupDigitalGPIO(PortA, pin3, OUTPUT, NoINTERRUPT);
    //Green
    SetupDigitalGPIO(PortA, pin2, OUTPUT, NoINTERRUPT);

    //East pins
    //Red
    SetupDigitalGPIO(PortD, pin1, OUTPUT, NoINTERRUPT);
    //Yellow
    SetupDigitalGPIO(PortD, pin2, OUTPUT, NoINTERRUPT);
    //Green
    SetupDigitalGPIO(PortD, pin3, OUTPUT, NoINTERRUPT);


    unsigned int volatile *pGPIODATA_A = (unsigned int *) (PortA + GPIODATA);
    unsigned int volatile *pGPIODATA_C = (unsigned int *) (PortC + GPIODATA);
    unsigned int volatile *pGPIODATA_D = (unsigned int *) (PortD + GPIODATA);
    int switch_position = *pGPIODATA_D & 0x80;
    int count = 0;
    while (1)
    {
        switch_position = *pGPIODATA_D & 0x80;
        if (switch_position != 128)
        {
            //If switch position is turned on turn all red lights on and all other lights off
            *pGPIODATA_C = *pGPIODATA_C | 0x80;
            *pGPIODATA_C = *pGPIODATA_C & ~0x40;
            *pGPIODATA_C = *pGPIODATA_C & ~0x20;

            *pGPIODATA_A = *pGPIODATA_A | 0x20;
            *pGPIODATA_A = *pGPIODATA_A & ~0x40;
            *pGPIODATA_A = *pGPIODATA_A & ~0x80;

            *pGPIODATA_A = *pGPIODATA_A | 0x10;
            *pGPIODATA_A = *pGPIODATA_A & ~0x08;
            *pGPIODATA_A = *pGPIODATA_A & ~0x04;

            *pGPIODATA_D = *pGPIODATA_D | 0x02;
            *pGPIODATA_D = *pGPIODATA_D & ~0x04;
            *pGPIODATA_D = *pGPIODATA_D & ~0x08;
            break;
        }
    else
    {
        count = count + 1;
//Based on count turn different colored lights on and off
        if (count < 300000)
        {
            *pGPIODATA_C = *pGPIODATA_C | 0x80;
            *pGPIODATA_A = *pGPIODATA_A | 0x20;
            *pGPIODATA_A = *pGPIODATA_A | 0x10;
            *pGPIODATA_D = *pGPIODATA_D | 0x02;
        }
        else if (300000 < count && count < 900000)
        {
            *pGPIODATA_C = *pGPIODATA_C & ~0x80;
            *pGPIODATA_A = *pGPIODATA_A & ~0x20;
            *pGPIODATA_C = *pGPIODATA_C | 0x20;
            *pGPIODATA_A = *pGPIODATA_A | 0x80;

        }
        else if (count > 900000 && count < 1200000)
        {
            *pGPIODATA_C = *pGPIODATA_C & ~0x20;
            *pGPIODATA_A = *pGPIODATA_A & ~0x80;
            *pGPIODATA_C = *pGPIODATA_C | 0x40;
            *pGPIODATA_A = *pGPIODATA_A | 0x40;

        }
        else if (count > 1200000 && count < 1500000)
        {
            *pGPIODATA_C = *pGPIODATA_C & ~0x40;
            *pGPIODATA_A = *pGPIODATA_A & ~0x40;
            *pGPIODATA_C = *pGPIODATA_C | 0x80;
            *pGPIODATA_A = *pGPIODATA_A | 0x20;

        }
        else if (count > 1500000 && count < 2100000)
        {
            *pGPIODATA_A = *pGPIODATA_A & ~0x10;
            *pGPIODATA_D = *pGPIODATA_D & ~0x02;
            *pGPIODATA_A = *pGPIODATA_A | 0x04;
            *pGPIODATA_D = *pGPIODATA_D | 0x08;

        }
        else if (count > 2100000 && count < 2400000)
        {
            *pGPIODATA_A = *pGPIODATA_A & ~0x04;
            *pGPIODATA_D = *pGPIODATA_D & ~0x08;
            *pGPIODATA_A = *pGPIODATA_A | 0x08;
            *pGPIODATA_D = *pGPIODATA_D | 0x04;

        }
        else if (count > 2400000)
        {
            count = 0;
            *pGPIODATA_A = *pGPIODATA_A & ~0x08;
            *pGPIODATA_D = *pGPIODATA_D & ~0x04;

        }
    }
    }

}

Credits

Comments

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Rush Hour

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

How it Works

The Build

The Software

The Result

Schematics

Traffic System Diagram

Code

Traffic System Software

Credits

Katie Turner

Alan Tapper

Arjun Kannan

Pablo Solano

Albert Wan

Comments

Embed the widget on your own site

Rush Hour

Rush Hour

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

How it Works

The Build

The Software

The Result

Schematics

Traffic System Diagram

Code

Traffic System Software

Credits

Katie Turner

Alan Tapper

Arjun Kannan

Pablo Solano

Albert Wan

Comments

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