Tiva Lab Lab 02: Street Traffic Light

Exp#1.1 Implement Each Traffic Light Action into Statements

This involves creating specific functions for each traffic light sequence (Green, Yellow, Blinking Yellow, Red) and using timing control within these functions.

Pseudocode for Loop Control

// Initial state: East-West direction is Red, all others OFF
  Turn OFF all LEDs
  Turn ON  EW_RED

LOOP:
    // Cycle for North-South Direction (Green -> Yellow -> Blinking Yellow -> Red)
    // East-West remains Red
    Turn OFF NS_RED, and Turn ON NS_GREEN
    Delay for 10 seconds
    Turn OFF NS_GREEN, and Turn ON NS_YELLOW
    Delay for 3 seconds
    // Blinking North-South Yellow LED sequence
    FOR 2 cycles:
        Turn OFF NS_YELLOW
        Delay for 0.5 seconds
        Turn ON  NS_YELLOW
        Delay for 0.5 seconds
    Turn OFF NS_YELLOW, and Turn ON NS_RED
    Delay for 1 second

    // Prepare for East-West Direction cycle by setting North-South to Red
    // Cycle for East-West Direction (Green -> Yellow -> Blinking Yellow -> Red)
    // North-South remains Red
    Turn OFF EW_RED, and Turn ON EW_GREEN
    Delay for 10 seconds
    Turn OFF EW_GREEN, and Turn ON EW_YELLOW
    Delay for 3 seconds
    // Blinking East-West Yellow LED sequence
    FOR 2 cycles:
       Turn OFF EW_YELLOW
       Delay for 0.5 seconds
       Turn ON  EW_YELLOW
       Delay for 0.5 seconds
    Turn OFF EW_YELLOW, and Turn ON EW_RED
    Delay for 1 second
 
REPEAT LOOP

Advantages and Disadvantages

• Advantages: Simple, easy-to-understand, precise control over each LED state.
• Disadvantages: Hard to maintain and extend, code may become repetitive.

Exp#1.2 Implement Traffic Light Actions into Functions

Reorganize the code from Exp#1.1 into sub-functions for better readability and organization.

Each Action Function:

• Create separate functions for each light sequence.
• Use delays to manage timing.

northSouthGreen()
    Set NS_GREEN ON
    Delay for 10,000 ms
    Set NS_GREEN OFF

northSouthYellow()
    Set NS_YELLOW ON
    Delay for 3,000 ms
    Set NS_YELLOW OFF

northSouthBlinkingYellow()
    Two LOOPs:
        Set NS_YELLOW ON
        Delay for 500 ms
        Set NS_YELLOW OFF
        Delay for 500 ms

eastWestGreen()
    Set EW_GREEN ON
    Delay for 10,000 ms
    Set EW_GREEN OFF

eastWestYellow()
    Set EW_YELLOW ON
    Delay for 3,000 ms
    Set EW_YELLOW OFF

eastWestBlinkingYellow()
    Two LOOPs:
        Set EW_YELLOW ON
        Delay for 500 ms
        Set EW_YELLOW OFF
        Delay for 500 ms

Main Loop:

• Alternate between North-South and East-West light sequences.
• Ensure a red light pause between transitions.

// Initial state: East-West direction is Red, all others OFF
    Turn OFF all LEDs
    Turn ON  EW_RED

LOOP:
    // North-South Cycle
    Set NS_RED OFF
    northSouthGreen();
    northSouthYellow();
    northSouthBlinkingYellow();
    Set NS_RED ON;
    Delay for 1,000 ms          // Red for 1 second

    // East-West Cycle
    Set EW_RED OFF;
    eastWestGreen();
    eastWestYellow();
    eastWestBlinkingYellow();
    Set EW_RED ON;
    Delay for 1,000 ms          // Red for 1 second
Repeat LOOP

Exp#1.3: Use a Lookup Table Array

This involves defining a lookup table that stores the status and duration of each traffic light state, then writing code to read from this table and control the lights accordingly.

Pseudocode for Definitions

define structure of TRAFFIC_LIGHT_SEQUENCE_STRUCT = {LIGHT, DURATION_MS}

define _NS_LEDR      0x01       // Red    Light of North-South direction
define _NS_LEDY      0x02       // Yellow Light of North-South direction
define _NS_LEDG      0x04       // Green  Light of North-South direction
define _EW_LEDR      0x08       // Red    Light of East-West   direction
define _EW_LEDY      0x10       // Yellow Light of East-West   direction
define _EW_LEDG      0x20       // Green  Light of East-West   direction

Pseudocode for Traffic Light Sequence Array

TRAFFIC_LIGHT_SEQUENCE_STRUCT traffic_light_sequence = [
    { _EW_LEDR | _NS_LEDG, 10000},
    { _EW_LEDR | _NS_LEDY,  3000},
    {                    ,      },
    {                    ,      },
    {                    ,      },
    {                    ,      },
    {                    ,      },

    {                    ,      },
    {                    ,      },
    {                    ,      },
    {                    ,      },
    {                    ,      },
    {                    ,      },
    {                    ,      },
]

Pseudocode for Loop Control

index = 0
LOOP:
    light    = traffic_light_sequence[index].LIGHT
    duration = traffic_light_sequence[index].DURATION_MS
    Check _NS_LEDR bit in light is set, turn ON NS_RED;    otherwise turn it off
    Check _NS_LEDY bit in light is set, turn ON NS_YELLOW; otherwise turn it off
    Check _NS_LEDG bit in light is set, turn ON NS_GREEN;  otherwise turn it off
    Check _EW_LEDR bit in light is set, turn ON EW_RED;    otherwise turn it off
    Check _EW_LEDY bit in light is set, turn ON EW_YELLOW; otherwise turn it off
    Check _EW_LEDG bit in light is set, turn ON EW_GREEN;  otherwise turn it off
    Delay for duration ms
    index = (index + 1) % length(traffic_light_sequence)
Repeat LOOP

Advantages and Disadvantages

• Advantages: Easier to update and extend, reduces code redundancy.
• Disadvantages: More complex to implement, less direct control over individual states if special conditions are needed.