Hi all. Picked up my board 5 days ago and enjoyed playing with LED chasers and LCD library. Here is a little test I put together over the weekend for a bit of fun. All it does is repeatedly count from 0 to 255 in either binary or hex and swaps display mode when the button is pressed.
Hardware setup is jut the LCD example from this site with a button wired onto pin 10.
Feel free to critique (constrictively! 
) and provide ideas of how this can be cleaned up. My next step is to move the conversion functions into a library for re-use in future projects.
/**
* Binary/Hex count with mode button.
* Some code courtesy of arduino.cc, rest is my own!
*/
/* include the library code: */
#include <string.h>
#include <LiquidCrystal.h>
/* Constants */
#define BIN 0
#define HEX 1
#define BUTTONPIN 10
#define MAXVAL 256
#define BOUNCEDELAY 50
#define COUNTDELAY 1000
/* Initialize the library with the numbers of the interface pins */
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
byte countmode;
byte buttonstate;
byte prevstate;
byte current;
long int lastupdate;
long int currenttime;
void setup()
{
/* set up the LCD's number of rows and columns */
lcd.begin(16, 2);
/* Configure the pushbutton pin */
pinMode(BUTTONPIN, INPUT);
/* Initialise variable values */
lastupdate = 0;
prevstate = LOW;
countmode = BIN;
current = 0;
/* Print a message to the LCD */
printheader(countmode);
}
void loop()
{
/* Handle the button */
buttonstate = digitalRead(BUTTONPIN);
if (buttonstate != prevstate)
{
/* Pause to allow noise to pass */
delay(BOUNCEDELAY);
if (buttonstate == HIGH)
{
/* Switch modes */
lcd.clear();
countmode = !countmode;
printheader(countmode);
prevstate = HIGH;
}
else
prevstate = LOW;
}
printval(current, countmode);
currenttime = millis();
if (currenttime - lastupdate > COUNTDELAY)
{
lastupdate = currenttime;
current = (current + 1) % MAXVAL;
}
}
void tobin(int dec, char *bin)
{
byte bitval = 128;
for (byte count = 0; count < 8; count++)
{
if (dec & bitval)
bin[count] = '1';
else
bin[count] = '0';
bitval >>= 1;
}
bin[8] = '\0';
}
void tohex(int toprint, char *hex)
{
hex[0] = hexchar(toprint >> 4);
hex[1] = hexchar(toprint & 0x0f);
hex[2] = 0;
}
char hexchar(char inval)
{
if (inval <= 9)
return inval + 48;
else
return inval + 55;
}
void printheader(byte mode)
{
if (mode == BIN)
lcd.print("Binary Counter");
else
lcd.print("Hex Counter ");
}
void printval(int val, byte mode)
{
char bitstring[9];
lcd.setCursor(0, 1);
if (mode == BIN)
tobin(val, bitstring);
else
tohex(val, bitstring);
lcd.print(bitstring);
}