Why doesn't PSOC 5LP print this number?

Question

I'm using CY8CKIT-050 PSOC 5LP development kit and I have this code:

#include "project.h"
#include<stdio.h>

int main(void)
{
    CyGlobalIntEnable; /* Enable global interrupts. */

    float32 test;

    LCD_Start();

    for(;;)
    {
        test = 0.1;
        sprintf(lineStr, "Test: %.2f", test);

        LCD_Position(1u, 0u);
        LCD_PrintString("                    ");

        LCD_Position(1u, 0u);
        LCD_PrintString(lineStr);

    }

But when I connect the LCD to the board, it doesn't appear 0.1, but 0.. However, when test=0.0, it apears Test: 0.000000.

I hope someone can help me. Thank you for your responses.

Obviously the word Test: appears, but I thought it was so obvious that I didn't have to mention. It's displayed Test: 0. — Josemi, Apr 08 '19 at 14:56
If you look at the responses, you can see in the last one I have said that I even removed the word "Test:", but nothing changed — Josemi, Apr 08 '19 at 15:07
what happens if you use sprintf(lineStr, "Test: %.2f", 0.1);? — jsotola, Apr 08 '19 at 15:09
What happens if you move the LCD_PrintString that blanks the display to before the for(;;) loop? — srl100, Apr 08 '19 at 15:18
Have you tried other values (e.g. 2.5) or without the .2 precision specifier? — srl100, Apr 08 '19 at 15:21
I have tried right now and it seems that anything appears after a nonzero digit. For example, for 2.5 doesn't appear anything (with and without the .2 especifier) — Josemi, Apr 08 '19 at 15:33
It looks to me like the floating point output is broken, since you say that it shows "0.000000" even when you have a ".2" precision specifier (so it should show "0.00"). — srl100, Apr 08 '19 at 15:41
Embedded toolchains typically omit floating point functionality from printf related functions. — uglyoldbob, Apr 08 '19 at 19:33

score 3 · Answer 1 · answered Apr 08 '19 at 14:41

3

It looks like test is defaulting to an integer datatype, unless you have declared it otherwise in one of your header files. Your real literal, 0.1, is being truncated (i.e. floored, rounded-down) to integer 0.

You must declare test to be a floating-point datatype.

answered Apr 08 '19 at 14:41

Elliot Alderson

31,521
5
30
67

One more reason to read what the compiler warnings are about. :D – Richard the Spacecat Apr 08 '19 at 14:43
Sorry, I forgot the declaration of test, it is actually a float but still doesn't work – Josemi Apr 08 '19 at 14:43

srl100 · Answer 2 · 2019-04-08T15:11:07.937

0

[Referring to an earlier version of the question text.]

"Test: 0." contains 8 characters (not including the nul at the end) - is this the width of your LCD?

Try using LCD_PrintString("0123456789ABCDEF"); and see how many characters are displayed.

edited Apr 08 '19 at 15:11

answered Apr 08 '19 at 14:52

srl100

179
4

It has 16 characters, so I think that's not a problem – Josemi Apr 08 '19 at 14:57
Try the print anyway, you might find that your (software) driver only thinks that the display is 8 characters wide! – srl100 Apr 08 '19 at 14:58
I even removed the word "Test:", but nothing changed. – Josemi Apr 08 '19 at 14:59
1

where is lineStr defined? – JayEye Apr 08 '19 at 15:27

Why doesn't PSOC 5LP print this number?

2 Answers2