Multiple pins within a function argument - c

Question

Hello Stackoverflow users!
It's the line trafiksignal(redLed && yellowLed, 1000); I can't get to work, I'm trying to create a trafic signal using a function, and my idea was to use this picture as a guide: http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Traffic_lights_4_states.png/220px-Traffic_lights_4_states.png
(can't post pictures due to rep < 10)
My code: http://pastebin.com/MTGsYeXs
/*
* #Author: Kristian Nymann
* #Date: 2014-09-25 22:46:39
* #Last Modified by: Kristian Nymann
* #Last Modified time: 2014-09-25 23:23:19
* #Description: Lav et program der får de tre lysdioder til at skifte som et trafiklys. Du kan brugeprogrammet "Blink" som eksempel.
*/
const byte greenLed = 2;
const byte yellowLed = 3;
const byte redLed = 4;
void setup() {
pinMode(greenLed, OUTPUT);
pinMode(yellowLed, OUTPUT);
pinMode(redLed, OUTPUT);
}
void loop() {
trafiksignal(redLed, 3000);
trafiksignal(redLed && yellowLed, 1000);
trafiksignal(greenLed, 3000);
trafiksignal(yellowLed, 1000);
}
void trafiksignal(byte pin, unsigned int duration)
{
digitalWrite(pin, HIGH);
delay(duration);
digitalWrite(pin, LOW);
}
Right now what's going on is:
Red led turns on for 3 sec.. then green led turns on for 3 sec, then yellow turns on for 1 sec..
So how can I make the yellow and red Led turn on at the same time? (why doesn't trafiksignal(redLed && yellowLed, 1000); work?)

Answer 1

As far as I am aware && in C is for logical comparison only.
trafiksignal(redLed && yellowLed, 1000);
What this line is basically doing is checking if redLed and yellowLed are true or false, and if they're both true it will send a 1 or if either are false it will send a 0. Since both of them are not 0 it should treat them as both true so you're actually most likely telling pin 1 to go high for 1 second instead of pin 3 and 4.
A few simple work around would be to either create a separate function for turning the red and yellow light off or putting a quick if clause inside trafiksignal functio. Bellow is a quick a dirty if statement to add to trafiksignal that should get you up and running with your current code.
if (pin == 1) {
digitalWrite(3, HIGH);
digitalWrite(4, HIGH);
delay(duration)
digitalWrite(3, LOW);
digitalWrite(4, LOW);
}
else {
digitalWrite(pin, HIGH);
delay(duration);
digitalWrite(pin, LOW);
}
Typed the code from my ipad so I would proof read it before copy and pasting.
edited from my computer:
A better solution would be to send the pins to the function as an array, i'm not super experienced in plain C so I'm not sure if what i've done bellow is 100% accurate but it should be fairly close.
const byte greenLed = 2;
const byte yellowLed = 3;
const byte redLed = 4;
const byte redYellow[2] = {redLed, yellowLed} // create an array of 2 pins
void setup() {
pinMode(greenLed, OUTPUT);
pinMode(yellowLed, OUTPUT);
pinMode(redLed, OUTPUT);
}
void loop() {
// the middle number is the number of LEDs the function will need to control.
trafiksignal(redLed, 1, 3000);
trafiksignal(redYellow, 2, 1000);
trafiksignal(greenLed, 1, 3000);
trafiksignal(yellowLed, 1, 1000);
}
void trafiksignal(byte pin[], unsigned int numberOfLeds, unsigned int duration)
{
for (int i =0; i < numberOfLeds; ++i {
digitalWrite(pin[i], HIGH);
}
delay(duration);
for (int i = 0; i < numberOfLeds; ++i) {
digitalWrite(pin[i], LOW);
}
}