Can you sprintf in Arduino with SAMD

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I think you are refering to Arm mbed: Serial.printf() fails to emit floats when using platformio - #5 by valeros. These flags absolutely work. They are not STM32 specific, they are specific to arm-none-eabi-gcc’s C library, so it applies to all ARM targets.

If I do

[env:adafruit_feather_m0]
platform = atmelsam
board = adafruit_feather_m0
framework = arduino
build_flags = -Wl,-u_printf_float
monitor_speed = 115200
monitor_dtr = 1

with code

#include <Arduino.h>

void setup() { Serial.begin(115200); }
void loop() {
   char charBuf[20] = {};
   float seconds = 1.3f;
   sprintf(charBuf, "Ping: %.2f (s)", seconds);
   Serial.println(charBuf);
   delay(1000);
}

I get

--- Miniterm on COM6  115200,8,N,1 ---
--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
Ping: 1.30 (s)
Ping: 1.30 (s)

So, no problems & no additional function needed. Just enable it in the C library.

If that still doesn’t work for you, post your complete platformio.ini.