wvmarle:
That's interesting.
Did you remember to update this line as well, when calibrating?
if (micros() - lastTick >= 1001500) {
Actually better code would be:
#define INTERVAL 1001500 // the actual length of a second in micros() as measured by the Arduino,
// change this to adjust the clock speed.
static unsigned long lastTick = 0;
if (micros() - lastTick >= INTERVAL) {
lastTick += INTERVAL;
second++;
}
This makes sure that every second is INTERVAL microseconds long. Otherwise indeed you may get a little drift, as depending on the rest of your code you could be a few milliseconds late ticking the second, meaning you start counting the next tick late if you would use micros() there again.
Thanks. I appreciate. The INTERVAL feature makes sense. But on the other hand, if I use that in my code (which I have included below) I find it harder to find the sweet spot in order to get the most accuracy possible out of arduino. Regardless of how fine I calibrate the INTERVAL value, it either gains too much or drifts behind. I am using values between 1001200-1001300. Whereas if I use only the micros(), I can get an accuracy of + or - 30 seconds for 24 hours. Any ideas? Perhaps, something to do with my code? Here is my code:
/*
An open-source binary clock for Arduino.
Based on the code from by Rob Faludi (http://www.faludi.com)
Code under (cc) by Daniel Spillere Andrade, www.danielandrade.net
http://creativecommons.org/license/cc-gpl
*/
int second=0, minute=0, hour=0; //start the time on 00:00:00
int munit,hunit,valm=0,valh=0,ledstats,i;
void setup() { //set outputs and inputs
pinMode(1, OUTPUT);pinMode(2, OUTPUT);pinMode(3, OUTPUT);pinMode(4, OUTPUT);pinMode(5, OUTPUT);
pinMode(6, OUTPUT);pinMode(7, OUTPUT);pinMode(8, OUTPUT);pinMode(9, OUTPUT);pinMode(10, OUTPUT);
pinMode(11, OUTPUT);pinMode(12, OUTPUT);pinMode(13, OUTPUT);
pinMode(0, INPUT);
}
void loop() {
#define INTERVAL 1001300
static unsigned long lastTick = 0;
if (micros() - lastTick >= INTERVAL) {
lastTick += INTERVAL;
second++;
}
// move forward one minute every 60 seconds
if (second >= 60) {
minute++;
second = 0; // reset seconds to zero
}
// move forward one hour every 60 minutes
if (minute >=60) {
hour++;
minute = 0; // reset minutes to zero
}
if (hour >=24) {
hour=0;
minute = 0; // reset minutes to zero
}
munit = minute%10; //sets the variable munit and hunit for the unit digits
hunit = hour%10;
ledstats = digitalRead(0); // read input value, for setting leds off, but keeping count
if (ledstats == LOW) {
for(i=1;i<=13;i++){
digitalWrite(i, LOW);}
} else {
//minutes units
if(munit == 1 || munit == 3 || munit == 5 || munit == 7 || munit == 9) { digitalWrite(1, HIGH);} else { digitalWrite(1,LOW);}
if(munit == 2 || munit == 3 || munit == 6 || munit == 7) {digitalWrite(2, HIGH);} else {digitalWrite(2,LOW);}
if(munit == 4 || munit == 5 || munit == 6 || munit == 7) {digitalWrite(3, HIGH);} else {digitalWrite(3,LOW);}
if(munit == 8 || munit == 9) {digitalWrite(4, HIGH);} else {digitalWrite(4,LOW);}
//minutes
if((minute >= 10 && minute < 20) || (minute >= 30 && minute < 40) || (minute >= 50 && minute < 60)) {digitalWrite(5, HIGH);} else {digitalWrite(5,LOW);}
if(minute >= 20 && minute < 40) {digitalWrite(6, HIGH);} else {digitalWrite(6,LOW);}
if(minute >= 40 && minute < 60) {digitalWrite(7, HIGH);} else {digitalWrite(7,LOW);}
//hour units
if(hunit == 1 || hunit == 3 || hunit == 5 || hunit == 7 || hunit == 9) {digitalWrite(8, HIGH);} else {digitalWrite(8,LOW);}
if(hunit == 2 || hunit == 3 || hunit == 6 || hunit == 7) {digitalWrite(9, HIGH);} else {digitalWrite(9,LOW);}
if(hunit == 4 || hunit == 5 || hunit == 6 || hunit == 7) {digitalWrite(10, HIGH);} else {digitalWrite(10,LOW);}
if(hunit == 8 || hunit == 9) {digitalWrite(11, HIGH);} else {digitalWrite(11,LOW);}
//hour
if(hour >= 10 && hour < 20) {digitalWrite(12, HIGH);} else {digitalWrite(12,LOW);}
if(hour >= 20 && hour < 24) {digitalWrite(13, HIGH);} else {digitalWrite(13,LOW);}
}
valm = analogRead(0); // add one minute when pressed
if(valm<800) {
minute++;
second=0;
delay(250);
}
valh = analogRead(5); // add one hour when pressed
if(valh<800) {
hour++;
second=0;
delay(250);
}
}