RE: Converting float value to string

garrettb — Mon, 26 Jun 2023 18:15:04 GMT

Well, the problem is right now that I can't use the strtof() function for anything. I get the following error:

undefined reference to `strtof'

So, similar to the issue of not being able to use the sprintf() with floats, until I set CONFIG_CBPRINTF_FP_SUPPORT=y in prj.conf, I wonder is there another setting I need to use the strtof() function?

RE: Converting float value to string

Hussam Aldean — Sat, 24 Jun 2023 05:14:34 GMT

Take the start of the float number and the end of it, create new string and pass it ti strtof.

RE: Converting float value to string

garrettb — Fri, 23 Jun 2023 19:16:02 GMT

Hi Hussam,

thank you, that worked.

Now I am trying to reverse the process, and convert a string to a float.

However if I try use atof() or strtof(), I get an "undefined reference" error.

Is there another library I need to include, or and extra switch to set in prj.conf?

Thanks

Garrett

RE: Converting float value to string

Hussam Aldean — Fri, 23 Jun 2023 18:00:59 GMT

add this to prj.conf

CONFIG_CBPRINTF_FP_SUPPORT=y

RE: Converting float value to string

garrettb — Fri, 23 Jun 2023 17:57:49 GMT

Hi Hussam, thanks for the reply.

No, that didn't work for me either.

I wonder is it to do with includes, or project settings?

I tried the following code:

    char dbg_buf1[16];
    char dbg_buf2[16];
    char dbg_buf3[16];
    char dbg_buf4[16];
    char dbg_buf5[16];
    float dbg_float = 12.345;
    double dbg_double = 54.321;
    int dbg_int = 1357;
    sprintf(dbg_buf1,"%0.2f",dbg_float);
    printk("Result 1: dbg_buf1 = %s\n", dbg_buf1);
    printk("Result 2: dbg_float = %0.2f\n", dbg_float);
    printk("Result 3: dbg_float = %f\n", dbg_float);
    sprintf(dbg_buf2,"%0.2f",dbg_double);
    printk("Result 4: dbg_buf2 = %s\n", dbg_buf2);
    printk("Result 5: dbg_double = %0.2f\n", dbg_double);
    printk("Result 6: dbg_double = %f\n", dbg_double);
    sprintf(dbg_buf3,"%0.2f",dbg_int);
    printk("Result 4: dbg_buf3 = %s\n", dbg_buf3);
    printk("Result 5: dbg_int = %0.2f\n", dbg_int);
    printk("Result 6: dbg_int = %f\n", dbg_int);
    sprintf(dbg_buf4,"%d",dbg_int);
    printk("Result 7: dbg_buf4 = %s\n", dbg_buf4);
    printk("Result 8: dbg_int = %d\n", dbg_int);
    printk("Result 9: dbg_int = %d\n", dbg_int);

With this result:

Result 1: dbg_buf1 = %0.2f
Result 2: dbg_float = %0.2f
Result 3: dbg_float = %f
Result 4: dbg_buf2 = %0.2f
Result 5: dbg_double = %0.2f
Result 6: dbg_double = %f
Result 4: dbg_buf3 = %0.2f
Result 5: dbg_int = %0.2f
Result 6: dbg_int = %f
Result 7: dbg_buf4 = 1357
Result 8: dbg_int = 1357
Result 9: dbg_int = 1357

I get the same result if I use LOG_INF() instead of printk().

Here are the file's includes:

#include <bluetooth/services/nus.h>
#include <dk_buttons_and_leds.h>
#include <errno.h>
#include <math.h>
#include <soc.h>
#include <stdio.h>
#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/gatt.h>
#include <zephyr/bluetooth/hci.h>
#include <zephyr/bluetooth/uuid.h>
#include <zephyr/device.h>
#include <zephyr/devicetree.h>
#include <zephyr/logging/log.h>
#include <zephyr/settings/settings.h>
#include <zephyr/sys/printk.h>
#include <zephyr/zephyr.h>

And the prj.conf file:

# Enable bonding
CONFIG_BT_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_SETTINGS=y

# Enable DK LED and Buttons library
CONFIG_DK_LIBRARY=y

# This example requires more workqueue stack
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

# Config logger
CONFIG_LOG=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n

CONFIG_ASSERT=y

CONFIG_NVS_LOG_LEVEL_DBG=y
CONFIG_REBOOT=y
CONFIG_MPU_ALLOW_FLASH_WRITE=y

RE: Converting float value to string

Hussam Aldean — Fri, 23 Jun 2023 03:15:57 GMT

How about sprintf(dbg_buf1,"%0.2f",dbg_float_val); ?