Standalone Atmega168...timing issue?

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1256871170

As per that thread, I just burned a sketch onto an Atmega168 that should display "Uptime = xxx" on an lcd (uptime being seconds that the atmega has been running. The LCD works great, but the time is erratic.. sometimes a second is short, sometimes it's long. I assume it's a timing issue, but I'm unsure how to troubleshoot the problem. Any suggestions?

2

hmmm, I just tried a sketch that does

led on
delay 1sec
led off
delay 1sec

and it seems to run accurately....

3

What's the code for the problematic example you gave above?

4

Ok so with the following code the LED appears to go on for a second/off for a second but the count on the LCD isn't accurate. It's as if the millis() function isn't functioning properly.

#include <LiquidCrystal.h>
//rs,enable
// initialize the lcd
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

void printTicks()
{
  lcd.setCursor(0, 0);

  char tickString[16] = "Uptime = ";
  char milliString[5];
  itoa(millis()/1000, milliString, 5);
  strcat(tickString, milliString);
  
  lcd.print(tickString);  
}

void setup() {
  pinMode(10, OUTPUT);
  
  lcd.begin(16, 2);
}

void loop() {
  
  // update the tick counter
  printTicks();
   
  digitalWrite(10, HIGH);
  delay (1000);
  digitalWrite(10, LOW);
  delay (1000);
}
5

Wow, this looks familiar....

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1232663936

I'm not using home though..

6

Boots,

I believe that the final argument to itoa() is the base (radix), not the string length. If so, your numbers would be printing out in base 5: 0, 1, 2, 3, 4, 10, 11, 12, 13, 14, 20, etc.

Change the final argument to 10. Also, increase your length of millistring[] to 10 or 20. Don't be too stingy with the bytes.

-Mike

7

Thanks Mike! That was totally the problem! Good eye!