How to display a number using LCDI2C4Bit.h library

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

Hi,

How can I display a number (reading sensor 0-1024) using LCDI2C4Bit.h library?
function printIn() - let me print a string, so meaby I should just convert int to string? But I do not know how to do it either.

one more question:

I have 2x16 display.
I want on the first row print “Hello”, on the sesond “World”.
I thought I should do it like this:

lcd.cursorTo(0,0);
lcd.printIn(“Hello”);
lcd.cursorTo(1,0);
lcd.printIn(“World”);

but there is only “Hello” on the first row…

Thanks for help!

#2

You can use the function itoa() to convert from integer to string. Something like this:

void loop()
{
  ...
  int intvalue = 512;
  char stringvalue[5];  // since your value is only 4 digits long
  
  itoa(intvalue, stringvalue, 10);
  ...
}

itoa function prototype is:

char *itoa( int value, char *string, int radix );

where value is the integer to convert (source), string is the destination and radix the numeric base (10 for decimal).

#3

The second line of an LCD is often not next to the first in its memory map so try:-
lcd.cursorTo(1,16);
lcd.printIn(“World”);

or

lcd.cursorTo(1,32);
lcd.printIn(“World”);

or

lcd.cursorTo(1,48);
lcd.printIn(“World”);

and so on.

or even:-

lcd.cursorTo(2,0);
lcd.printIn(“World”);

or

lcd.cursorTo(3,0);
lcd.printIn(“World”);
or
lcd.cursorTo(4,0);
lcd.printIn(“World”);

and so on.

#4

The second line of an LCD is often not next to the first in its memory map so try:-
lcd.cursorTo(1,16);
lcd.printIn(“World”);

It works, thanks!
Function itoa() works too. Another question… How to display a float number?

#5

[… Another question… How to display a float number?

Have a look at the code at the end of this thread: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1207226548

#6

How to display a float number?

the function is ftoa(). But I think floating point library would make your compiled program bigger.

#7

Thanks a lot!

#8

How to display a float number… the function is ftoa().

I didn’t see ftoa in stdlib.h when I went looking for this functionality in the avr gcc code distributed with the arduino. Where is it?

#9

How to display a float number… the function is ftoa().

I didn’t see ftoa in stdlib.h when I went looking for this functionality in the avr gcc code distributed with the arduino. Where is it?

Yes, checking out I found that avr-gcc doesn’t support ftoa(). You could use then sprintf() like here:

void loop()
{
  ...
  float floatvalue = 5.12;
  char stringvalue[10];
  
  sprintf(stringvalue, "%.2f", floatvalue);  // %.2f means to round decimal places to 2 digits. If you don' want to round then use %f
  ...
}
#10

How to display a float number… the function is ftoa().

I didn’t see ftoa in stdlib.h when I went looking for this functionality in the avr gcc code distributed with the arduino. Where is it?

Yes, checking out I found that avr-gcc doesn’t support ftoa(). You could use then sprintf() like here:

void loop()

{
 …
 float floatvalue = 5.12;
 char stringvalue[10];
 
 sprintf(stringvalue, “%.2f”, floatvalue);  // %.2f means to round decimal places to 2 digits. If you don’ want to round then use %f
 …
}



Have you tried these things you're suggesting? I don't think floating point is supported in sprintf either. Anyway, why use sprint which brings in almost 2k of code when there is a much smaller and easy to use function as per post #4 above.
#11