How to start a block of code after a certain time?

Question

I'm using a ATMega328P-PU on a breadboard as an arduino. How do you start a code after say 20 seconds have elapsed since startup? Example code:-

if(condition)
{
 //Start sending morse code!
}

My current code uses millis() and fails miserably. The speaker does not get activated. I'm using the standard circuit mentioned at the Arduino website My current code:-

time = millis();
 if(time>=20000)
 txEnable=true;
 val = analogRead(analogPin);
 if(val!=0)
 {
 standby=false;
 }
 else
 standby=true;
 if(txEnable==true && standby==true)
 {
 if(!callsignSender->continueSending())
 {
 callsignSender->startSending();
 }
 } 

• Edgar Bonet: You are comparing an analog reading with zero. Are you sure you don't mean digitalRead()? If you really need an analog value, instead of comparing with zero you should compare to some low threshold.
• Parth Sane: I'm basically writing this code for a ham wireless repeater. Its in Pune.(VU2PHA). The analog read value is for detecting any incoming signal for repeating. Its a small scale model for the same big repeater. The repeater custodian is my friend and I'm making it for him.
• Edgar Bonet: The define a "noise threshold" and treat any value below the threshold as equivalent to zero.
• Parth Sane: @Edgar Bonet I'm going to fine tune that once I get in touch with VU2ASH (one of the custodian). I'm making a protosketch.
• Parth Sane: I have to use the following protocol. docs.google.com/document/d/…

Answer 1

The following bare-minimum code will switch pin 13 to high after 20 seconds:

void setup() { 
 // assuming pin 13 has a LED connected (as on most Arduino boards)
 pinMode(13, OUTPUT); 
 digitalWrite(13, LOW); // would also work without this line
}
void loop() {
 unsigned long time = millis();
 if (time >= 20000) {
 digitalWrite(13, HIGH); // set the LED on
 }
}

Try if this works for you, i.e. if a LED connected to that pin will light up 20 seconds after reboot.

If not you will need to find the problem: Is your ATmega running at the correct speed? Is your code executed at all? Are the peripherals working?

• Parth Sane: millis() returns time in unsigned long format. Above code needs to be adjusted. (Otherwise its bound to create trouble) I'll try your code though. Pls try searching for alternatives!
• fuenfundachtzig: Well, it would work for what it's written. But I've changed it to ulong.
• fuenfundachtzig: Note that I don't suggest that you actually use code written like that for any other purpose than testing...