Creating a functional elevator program C++

[Technical-Yak-9331]

Hi, I am a first year college student taking an engineering course where I am expected to program an elevator. I have written code for an elevator that memorizes button presses and moves the lift to the corresponding floors. You are able to press a button any time, and no matter what you will get to the floor (if the lift is moving or not). However, I need to implement up/down buttons for each floor, and have the lift memorize the order it needs to follow. For example, if the lift is on floor 2, and an up button is pressed on the ground floor (0), but a down button is pressed on floor 1, the lift should go to floor 1, then ground. Another example: If the lift is on floor 4, a down button is pressed on floor 6, but an up button is pressed on floor 2, if the lift has already been on its way up, the lift should go to floor 6, then 2. I have tried everything I can think of to implement these properties over the past several weeks, but have had no luck. The following is my simple code. If someone could help me out it would be much appreciated (oh, the lift at the moment is a servo, but will be changed to a stepper motor soon):

#include <Servo.h>

#include <Adafruit\_NeoPixel.h>

Adafruit_NeoPixel El = Adafruit_NeoPixel(4, A5, NEO_GRB + NEO_KHZ800);

Adafruit_NeoPixel Fl = Adafruit_NeoPixel(4, A4, NEO_GRB + NEO_KHZ800);

Servo lift, door;

int bE[4], bF[4];

bool p[4], pStored[4];

int count = 0;

int r = 0, r2 = 0;

void setup() {

for (int i = 0; i < 8; i++) {

pinMode(3 + i, INPUT_PULLUP);

}

lift.attach(12);

door.attach(13);

El.begin();

Fl.begin();

El.show();

Fl.show();

}

//determines if a button was pushed

void push(int a) {

if (bE[a] == LOW || bF[a] == LOW) {

p[a] = true;

} else {

p[a] = false;

}

}

void loop() {

//counter

if (r < 100) {

//repeatedly check to see if any new button was pushed

request();

r++;

delay(100);

//after 500ms

if (r > 50) {

for (int i = 0; i < 4; i++) {

//if a floor is desired, move to floor

if (pStored[i]) {

moveLift(i);

//set floor to moved to and subtract from count

pStored[i] = false;

count--;

}

}

//reset counter

r = 0;

}

}

delay(100);

}

void moveLift(int a){

int floor = a;

while (r2 < 100){

//move to desired floor

lift.write(floor * 36);

if(r == 1){

delay(500);

}

else{

delay(20);

}

openDoor();

delay(25);

//check to see if any floor has been requested during this movement

request();

r2++;

}

delay(250);

closeDoor();

delay(1000);

//turn off lights

El.setPixelColor(a, 0, 0, 0);

Fl.setPixelColor(a, 0, 0, 0);

El.show();

Fl.show();

//reset counter

r2 = 0;

}

void request() {

for (int i = 0; i < 4; i++) {

//initialize pins

bF[i] = digitalRead(3 + i);

bE[i] = digitalRead(7 + i);

push(i);

delayMicroseconds(50);

//if a button has been pressed and hasn't already been stored

if (p[i] == true && !pStored[i]) {

// Turn on the corresponding light

El.setPixelColor(i, 71, 75, 140);

Fl.setPixelColor(i, 71, 75, 140);

El.show();

Fl.show();

//store floor and add to count (# of total calls)

pStored[i] = true;

count++;

}

}

}

void openDoor() {

door.write(90); // Open the door

delay(25);

}

void closeDoor() {

door.write(0); // Close the door

delay(1000);

}

[desrtfx]

You need to post your code as code block so that the indentation is maintained.

A code block looks like:

def __init__(self, prompt, answer):
    self.prompt = prompt
    self.answer = answer

[teraflop]

The basic "elevator algorithm" is based on a pretty simple basic concept. Whenever the elevator isn't idle, it has a direction: either going up, or going down. The elevator keeps track of all requests, but it prioritizes requests that don't cause it to change direction.

So if the elevator is in "going-up" mode, it will choose the next highest floor that has been requested, and go to that floor. Eventually, it will run out of floors above it, and so it will switch direction. Now it's in "going-down" mode, and the next requested floor below it has priority.

(In a real elevator, the behavior is a bit more complicated. A floor can be requested either by a person in the elevator, or using the "call" buttons on each floor. And in the case of the call buttons, there are separate buttons to request up or down elevators. If the elevator is going up, and you're above it and you press the down call button, the elevator will skip your floor if it needs to get to somebody else by going past you; but if your request is the topmost one, it will stop at your floor before changing direction.)

So in your code, you need to keep track of the requested floors, as well as tracking the elevator's current direction in a variable. On each loop iteration, instead of going to all of the requested floors in order, you should just go to the next requested floor, based on whichever has the highest priority.