SAMC21 Xplained Pro. AS6.2 AFS3.27
Here is the code:
c = 15.3;
/*main oop*/
while(1)
{
//c = 15.3;
d = c/3;
cntr = 10;
printf("Integer cntr= %d\r\n",cntr);
printf("Float d= %f\r\n",d); //PRINTF statement that doesn't print.
delay_s(2);
c=c+1.0;
cntr++;
}
here is the output:
clawson 
Does Arm have selectable printf library (like AVR)? For AVR at least there are 3 printf() libraries available, "minimal", "normal" and "float support". Only the latter shows %f output. Perhaps ARM is the same?
Interesting.
How can I select the float support library? As a linker -lprintf_flt
Now how can I find the libprintf_flt.a for the M0 core?
In the Atmel files so far I have only found the library for AVR8.
cmarciales 
I was looking for this answer, so I thought I'd post an answer in case you are using current tools (AtmelStudio 7).
In the project properties, under Toolchain, open the ARM/GNU Linker-->General options and DESELECT (uncheck)
the option "Use size optimized library". This will then increase your program size but will allow you to print
floats. If you are doing this for debug purposes, you can then check the option to once you don't need it.
Thanks for the answer.
but size jumps from 21K to 65K.
Found this on Atmel FAQ:
http://atmel.force.com/support/a...
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awneil 
but size jumps from 21K to 65K.
Which should come as no surprise at all!
On a processor with no hardware floating point (such as a Cortex-M0) it does take a "lot" of code to do floating point - which is why it's often avoided in small micros.
So - do you really need floating point ... ?
In this thread I was talking about the overhead of using "printf" for floats, not using floats.
Here are some tests on a D21 Xplained pro, AS 1188, ASF 3.32.
The code size difference is:
Integers only:
Program Memory Usage : 2264 bytes 0.9 % Full
Data Memory Usage : 9304 bytes 28.4 % Full
With float, but not using float printf.
Program Memory Usage : 2076 bytes 0.8 % Full
Data Memory Usage : 9304 bytes 28.4 % Full
With float, but not using float printf.
so the overhead of using software float is not great.
//test code for D21 Xplained using integers ASF 3.32
#include "sam.h"
#include "stdio.h"
#define SHIFT 32
volatile uint32_t ival,knt;
static uint64_t long_division(uint64_t n, uint64_t d)
{
int32_t i;
uint64_t q = 0, r = 0, bit_shift;
for (i = 63; i >= 0; i--) {
bit_shift = (uint64_t)1 << i;
r = r << 1;
if (n & bit_shift) {
r |= 0x01;
}
if (r >= d) {
r = r - d;
q |= bit_shift;
}
}
return q;
}
uint32_t bval(uint32_t peripheral_clock,uint32_t baudrate)
{
/* Temporary variables */
uint64_t ratio = 0;
uint64_t scale = 0;
uint64_t baud_calculated = 0;
uint64_t temp1;
uint32_t sample_num = 16;
/* Calculate the BAUD value */
temp1 = ((sample_num * (uint64_t)baudrate) << SHIFT);
ratio = long_division(temp1, peripheral_clock);
scale = ((uint64_t)1 << SHIFT) - ratio;
baud_calculated = (65536 * scale) >> SHIFT;
return ((uint32_t) baud_calculated);
}
int main(void)
{
uint32_t tval = 48000000UL;
uint32_t tbaud = 9600UL;
/* Initialize the SAM system */
SystemInit();
/* Replace with your application code */
while (1)
{
ival = bval(tval,tbaud);
knt++;
}
}
Task "RunOutputFileVerifyTask"
Program Memory Usage : 2264 bytes 0.9 % Full
Data Memory Usage : 9304 bytes 28.4 % Full
Done executing task "RunOutputFileVerifyTask".
//test code #2 for D21 Xplained using Floats ASF 3.32
#include "sam.h"
#include "stdio.h"
#define SHIFT 32
volatile uint32_t ival,knt;
uint32_t bval(uint32_t peripheral_clock,uint32_t baudrate)
{
/* Temporary variables */
uint32_t baud_calculated = 0;
float temp1;
uint32_t sample_num = 16;
/* Calculate the BAUD value */
temp1 = (((sample_num)*(float)baudrate)) / ((float)peripheral_clock);
baud_calculated = (uint32_t) (65536*(1 - temp1));
return ((uint32_t) baud_calculated);
}
int main(void)
{
uint32_t tval = 48000000UL;
uint32_t tbaud = 9600UL;
/* Initialize the SAM system */
SystemInit();
/* Replace with your application code */
while (1)
{
ival = bval(tval,tbaud);
knt++;
}
}
Task "RunOutputFileVerifyTask"
Program Memory Usage : 2076 bytes 0.8 % Full
Data Memory Usage : 9304 bytes 28.4 % Full
Done executing task "RunOutputFileVerifyTask".
awneil In this thread I was talking about the overhead of using "printf" for floats, not using floats.
Obviously, for printf to support floats - it has to include all the code for floats!
And that's on top of the code for rest of the printf functionality - which is quite a lot!
Yes, but my point is that using floats is independent of using printf for floats.
Using floats does not add much overhead.
Harikrishnan911 
HI,
Am using Atmel Studio 7 & also am unable to use floating point in my program.