Arduino wave generator - arduino

Question

I need to create an Arduino Wave Generator, but I realy can't get it to work properly.
The generator must output Sine, Square, Triangle and Sawtooth waves, I got the square one working, I tried a lot of things, but can't get the others to work properly.
Here's my circuit:
And here's the code that I'm using
int led1 = 3;
int led2 = 4;
int led3 = 5;
int led4 = 6;
int display = 13;
int inBtn = 8;
int btnSt = 0;
int btnLastSt = 0;
int cont = 0;
void setup() {
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(led4, OUTPUT);
pinMode(display, OUTPUT);
pinMode(inBtn, INPUT);
}
void loop() {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
switch(cont){
case 0:
digitalWrite(led1, HIGH);
digitalWrite(display, HIGH);
delay(250);
digitalWrite(display, LOW);
delay(250);
break;
case 1:
digitalWrite(led2, HIGH);
break;
case 2:
digitalWrite(led3, HIGH);
break;
case 3:
digitalWrite(led4, HIGH);
break;
}
if (digitalRead(inBtn) == LOW) {
cont++;
delay(150);
}
if (cont == 4) cont = 0;
if (btnLastSt != cont){
btnLastSt = cont;
}
}
The others waves would go inside the other 'cases'.
I'm sorry about the lack of info and research, but at this point I'm quite desperate (it's an assignment).
If someone could help me a bit on this, would be great.
UPDATE
Here's my final circuit and code, after Gerhard's help.
int led1 = 3;
int led2 = 4;
int led3 = 5;
int led4 = 6;
int display = 11;
int inBtn = 8;
int btnSt = 0;
int btnLastSt = 0;
int cont = 0;
void setup() {
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(led4, OUTPUT);
pinMode(display, OUTPUT);
pinMode(inBtn, INPUT);
}
void loop() {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
switch(cont){
case 0:
//Square
digitalWrite(led1, HIGH);
digitalWrite(display, HIGH);
delay(200);
digitalWrite(display, LOW);
delay(200);
break;
case 1:
//Sawtooth
digitalWrite(led2, HIGH);
for(int i = 0; i < 255; i++){
analogWrite(display, i);
delay(1);
}
analogWrite(display, 0);
delay(1);
break;
case 2:
//Triangular
digitalWrite(led3, HIGH);
for (int i = 0; i < 254; i++){
analogWrite(display, i);
delay(1);
}
for (int i2 = 254; i2 > 0; i2--){
analogWrite(display, i2);
delay(1);
}
break;
case 3:
//Sine
digitalWrite(led4, HIGH);
analogWrite(display, 10); delay(10);
analogWrite(display, 19); delay(10);
analogWrite(display, 45); delay(10);
analogWrite(display, 84); delay(10);
analogWrite(display, 130); delay(10);
analogWrite(display, 176); delay(10);
analogWrite(display, 215); delay(10);
analogWrite(display, 241); delay(10);
analogWrite(display, 250); delay(10);
analogWrite(display, 241); delay(10);
analogWrite(display, 215); delay(10);
analogWrite(display, 176); delay(10);
analogWrite(display, 130); delay(10);
analogWrite(display, 84); delay(10);
analogWrite(display, 45); delay(10);
analogWrite(display, 19); delay(10);
break;
}
if (digitalRead(inBtn) == LOW) {
cont++;
delay(100);
}
if (cont == 4) cont = 0;
if (btnLastSt != cont){
btnLastSt = cont;
}
}
It's not perfect, but it's good enough haha.

Answer 1

Your hardware setup is insufficient for what you want to achieve.
You need an analog output but you are using a digital output. You have to add a DAC (Digital to Analog Converter) (MAX98357A example) or use the PWM (Pulse Width Modulation) outputs (pins 3,5,6,9-11). Both of these would also require an additional LPF (low pass filter) on the output.
For PWM you setup the output pinMode(pin, OUTPUT) and can then use analogWrite(pin, value) with values on a scale of 0 - 255.