I can not use %f

Koichirou_Nishimura · September 1, 2023, 3:00am

Hello, I use Keil studio mbed OS6.13 and make project with blink LED example.
I try to use Buffered print like

        num = sprintf(buf, "ch%d: %.2f  ",i, v[i]);
        serial_port.write(buf, num);

but, it’s not work.

And I found this one

github.com

ARMmbed/mbed-os/blob/master/platform/source/minimal-printf/README.md

# Minimal printf and snprintf


Library supports both printf and snprintf in around 1300 bytes of flash.

Prints directly to stdio/UART without using malloc. Width size and prepending zero modifiers are supported. All other flags are ignored.
There is no error handling if a writing error occurs.

Supports:
* %d: signed integer [h, hh, (none), l, ll, z, j, t].
* %i: signed integer [h, hh, (none), l, ll, z, j, t].
* %u: unsigned integer [h, hh, (none), l, ll, z, j, t].
* %x: unsigned integer [h, hh, (none), l, ll, z, j, t], printed as hexadecimal number (e.g., ff).
* %X: unsigned integer [h, hh, (none), l, ll, z, j, t], printed as hexadecimal number (e.g., FF).
* %f: floating point (disabled by default). Precision modifier is supported (e.g. %.5f).
* %F: floating point (disabled by default, treated as %f). Precision modifier is supported (e.g. %.5F).
* %g: floating point (disabled by default, treated as %f). Precision modifier is supported (e.g. %.5g).
* %G: floating point (disabled by default, treated as %f). Precision modifier is supported (e.g. %.5G).
* %c: character.
* %s: string.

This file has been truncated. show original

but, there is no “mbed_app.json”.

Then I try to modify mbed_config.h like below
#define MBED_CONF_PLATFORM_MINIMAL_PRINTF_ENABLE_64_BIT 1
#define MBED_CONF_PLATFORM_MINIMAL_PRINTF_ENABLE_FLOATING_POINT 1
#define MBED_CONF_PLATFORM_MINIMAL_PRINTF_SET_FLOATING_POINT_MAX_DECIMALS 6

It still not work.
Anyone know how to use %f on Keil studio?

JohnnyK · September 1, 2023, 5:47am

Hello,

you are close, but it is not related to KeilStudio but to MbedOS configuration system

if the mbed_app.json is not already in your project, then should be created in root folder of your project - for more take a look to The configuration system - Program setup | Mbed OS 6 Documentation
Never modified mbed_config.h because it has no effect.
Line 18-19 of mbed_config.h file says -

// Automatically generated configuration file.
// DO NOT EDIT, content will be overwritten.

BR, Jan

Koichirou_Nishimura · September 1, 2023, 8:55am

Thank you! It works!

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I can not use %f

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