But I can't wrap my head around what the snprintf( ) command is/does.
I don't understand what it is that you don't understand...
The xxprintf(xxstuff, "format string", arg1, arg2, ...) functions all print the contents of the format string, with a variable number of arguments that are translated … Answer from westfw on forum.arduino.cc
Arduino Forum
forum.arduino.cc › projects › general guidance
Snprintf clarification - General Guidance - Arduino Forum
October 8, 2025 - I'll preface this by saying I'm a mechanical engineer who's been asked to build a device and also look at the programming, the mechanical bit is easy, I'm struggling a little with some of the programming; I'm using a Nano R4 and LoRa wan shield to send some data to a "things" server, I've pulled ...
Reddit
reddit.com › r/arduino › snprintf works with integers but not with floats.
r/arduino on Reddit: snprintf works with integers but not with floats.
January 7, 2024 -
I am getting a bit confused and I need some help.The following code works fine:
const uint8_t MESSAGE_MAX_SIZE = 10;
char message[MESSAGE_MAX_SIZE];
uint8_t val ;
val = 99;
(void)snprintf(message, MESSAGE_MAX_SIZE,"%d", val);
Serial.println(message);whereas the following does not:
const uint8_t MESSAGE_MAX_SIZE = 10;
char message[MESSAGE_MAX_SIZE];
float val ;
val = 1.23;
(void)snprintf(message, MESSAGE_MAX_SIZE,"%f", val);
Serial.println(message);Firstly, I get the following warning:
(32 of 107): warning: format '%f' expects argument of type 'double', but argument 4 has type 'float' [-Wformat=]
and what I get from the serial is the character ?.
If I accommodate the warning with e.g.:
(void)snprintf(message, MESSAGE_MAX_SIZE,"%f", (double)val);
then I get the same result, i.e. ? from the serial.
Top answer 1 of 5
10
Yeah, avr-libc disables float formatting by default because it takes tons of flash space to cover all possible formats and edge conditions that floats allow. Use dtostrf() as others note which has heavily minimized float formatting code
2 of 5
3
I believe you need to convert the float to a string. Found this forum post: https://forum.arduino.cc/t/sprintf-with-float-values/937562/13 And this tutorial on the dtostrf function: https://www.programmingelectronics.com/dtostrf/
Useless messages using < sprintf() and snprintf()>
Hi all, I don't know if this is related to Arduino IDE or not... However, when I use < snprintf() > in Arduino IDE 2.3.4 and run 'Verify' (Ctrl + R), I get these two messages: More on github.com
5
December 11, 2024arduino - Custom snprintf() function gives wrong output - Stack Overflow
Background I'm trying to write a wrapper function for snrpintf() on an embedded platform (Arduino) to have a shorthand for writing into a buffer then printing it over the Serial port. Problem As... More on stackoverflow.com
c string - snprintf doesn't display float values - Arduino Stack Exchange
I don't understand why the formatted string is displaying ?? instead of float values. My code: #include #include #include "SparkFunCCS811.h" #include More on arduino.stackexchange.com
how to snprintf to serial with String object type ?
Hello, I would like to run the following simple code to simulate my problem: typedef struct { String sensorName; byte pin; byte state; } sensorData; // sensors on this node {sensorname,pinnr,begin_state} sensorData sensorTable[6] = { {"POG04",1,0}, {"POG14",1,0}, {"ROG04",1,0}, {"ROG14",1,0}, ... More on forum.arduino.cc
2
0
September 18, 201111:20
Formatea String en Array con snprintf en Arduino con ESP32 y ESP8266 ...
08:34
If you don’t learn sprintf(), your code will hate you later - ...
04:08
Arduino101-3 Simple number conversion with String - YouTube
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Arduino Forum
forum.arduino.cc › projects › programming
snprintf() - stuck - Programming - Arduino Forum
March 11, 2018 - Folks, I AM trying, but find it frustrating when I search and get a "File not found" when I click on a link; snprintf() search on google I am really not getting how things are explained in this case and many others. S…
Programming Electronics Academy
programmingelectronics.com › home › sprintf() with arduino | print multiple variables to the serial monitor
sprintf() with Arduino | Print multiple variables to the serial monitor
November 13, 2023 - Sprintf() with Arduino cannot handle floating point values. So if you have to print something that has a decimal point, like 3.14 or 156.7, then you need to convert that float value to a character string first, and then print the string.
Zbotic
zbotic.in › home › arduino string formatting: sprintf, dtostrf and print tips
Arduino String Formatting: sprintf, dtostrf and Print Tips - Zbotic
May 20, 2026 - Regular sprintf() has a critical vulnerability: if your format string produces more characters than the buffer can hold, it writes past the end of the buffer — a classic buffer overflow. On Arduino, this can corrupt the stack, cause seemingly random crashes, or corrupt other variables. snprintf(buffer, maxLen, format, args...) adds a maximum length parameter:
E-tinkers
e-tinkers.com › 2020 › 01 › do-you-know-arduino-sprintf-and-floating-point
Do you know Arduino? – sprintf and floating point – E-Tinkers
T> void print(const char *str, T... args) { int len = snprintf(NULL, 0, str, args...); if (len) { char buff[len+1]; snprintf(buff, len+1, str, args...); Serial.print(buff); } } Now I have a one liner print() function that is elegant and easy to read: print("temperature = %.1fc, Humidity = %.1f%%\n", temp, humidity); After done all those research and implement my own print function, I'm wondering how other Arduino-compatible platforms handle floating point in their Arduino core implementation?
GitHub
github.com › espressif › arduino-esp32 › issues › 10716
Useless messages using < sprintf() and snprintf()> · Issue #10716 · espressif/arduino-esp32
December 11, 2024 - void setup() { Serial.begin(9600); // const uint8_t kBffrSize8 = 6; uint16_t decVal16 = 3; // any value between 0 and 4095 MAX.(0xFFF) char ary_hexNUM[kBffrSize8]; // snprintf(ary_hexNUM, kBffrSize8, "0xX", decVal16); // Serial.print(F("ary_hexNUM[-3-] ==> ")); for (uint8_t i = 0; i < 6; i++) Serial.print(ary_hexNUM[i]); Serial.println(); // } // setup() void loop() { // } // loop()
Author espressif
Vilimpoc
vilimpoc.org › blog › 2015 › 11 › 18 › sprintf-snprintf-problem-on-arduino
sprintf / snprintf Problem on Arduino.
/** * Demonstrate that the sprintf / snprintf implementation on Arduino is broken. * * sprintf / snprintf, when used with more than 8 varargs: * inserts an extra '00' in the output string * removes the last parameter from the output string * * This causes a lot of extra debugging.
Wolles Elektronikkiste
wolles-elektronikkiste.de › startseite › formatted output
Formatted output • Wolles Elektronikkiste
September 2, 2024 - For formatted output on the serial monitor or on displays, you can use the convenient functions sprintf() and snprintf().
C++ for Arduino
cpp4arduino.com › 2020 › 02 › 07 › how-to-format-strings-without-the-string-class.html
How to format strings without the String class | C++ for Arduino
February 7, 2020 - Before we say goodbye, I’ll like to present my all-time favorite function of the whole Arduino ecosystem. It’s snprintf_P(), but I call it “the holy grail” because it’s a hidden treasure that does everything one would want. It is identical to snprintf() except that it reads the format string from the Flash memory, and therefore reduces the RAM consumption.
Stack Exchange
arduino.stackexchange.com › questions › 80401 › snprintf-doesnt-display-float-values
c string - snprintf doesn't display float values - Arduino Stack Exchange
#include <Arduino.h> #include <Wire.h> #include "SparkFunCCS811.h" #include <DFRobot_SHT3x.h> DFRobot_SHT3x sht3x(&Wire, /*address=*/0x44, /*RST=*/4); //* Get SHT31 readings void readSHT(float &temp, float &humid) { DFRobot_SHT3x::sRHAndTemp_t data = sht3x.readTemperatureAndHumidity(sht3x.eRepeatability_High); char shtVal[50]; if (data.ERR == 0) { temp = data.TemperatureC; humid = data.Humidity; Serial.println(data.TemperatureC); Serial.println(data.Humidity); } snprintf(shtVal, 50, "Temp = %f Humidity = %f", temp, humid); Serial.println(shtVal); } void setup() { Serial.begin(115200); //*Initi
Arduino Forum
forum.arduino.cc › projects › programming
how to snprintf to serial with String object type ? - Programming - Arduino Forum
September 18, 2011 - Hello, I would like to run the following simple code to simulate my problem: typedef struct { String sensorName; byte pin; byte state; } sensorData; // sensors on this node {sensorname,pinnr,begin_state} sensorData sensorTable[6] = { {"POG04",1,0}, {"POG14",1,0}, {"ROG04",1,0}, {"ROG14",1,0}, {"LOG04",1,0}, {"TOG04",1,0} }; void setup() { Serial.begin(57600);}; int debug =1; // function to write data to Log void writeLog(char* msg) { if (debug == 1) {Serial.println(msg);...
Top answer 1 of 16
1
Use %S instead of %s when using F() for the parameter.
2 of 16
0
[image] UKHeliBob:
What if someone is in a position to suggest an alternative way to do what you want that may be better in some way ?
Please go ahead and suggest away. I am not opposed to improvements or alternatives. It's just that I had difficulty finding out how to do stuff, and more info…
Top answer 1 of 2
6
Arduino's implementation of snprintf has no floating-point support. Had to use dtostrf instead (http://www.nongnu.org/avr-libc/user-manual/group__avr__stdlib.html#ga060c998e77fb5fc0d3168b3ce8771d42).
So instead of doing:
char temp[100];
float f;
f = 1.23;
snprintf(temp, 100, "%f", f);
Using the Arduino i had to do:
char temp[100];
float f;
f = 1.23;
dtostrf(f , 2, 2, temp); //first 2 is the width including the . (1.) and the 2nd 2 is the precision (.23)
These guys had figured that out on the avrfreaks forum: http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=119915
2 of 2
-3
Considering what you meant is
char temp[100];
float f;
f = 1.23;
snprintf(temp, 100, "%f", f);
it works as it's supposed to.
Arduino Forum
forum.arduino.cc › projects › programming
[SOLVED] Problem with snprintf and signed and unsigned long - Programming - Arduino Forum
January 27, 2014 - Hi I want to use signed long and unsigned long with snprintf. after some reading up I think I should use the ul and il tag. However that does not give me the wanted result. For instance: void setup() { // put your setup code here, to run once: delay(1000); } void loop() { // put your main code here, to run repeatedly: static unsigned long smallUnsigned =1; static unsigned long bigUnsigned =100000; static unsigned long smallSigned =-100000; static unsigned long bigSigned =1000...
Arduino Forum
forum.arduino.cc › projects › programming
Snprint With String Values - Programming - Arduino Forum
December 26, 2021 - Hello, I am trying to use the newly released Microsoft Azure IOT library. There is a line in the initial sketch which I have modified heavily that states. // replace the following line with your data sent to Azure IoTHub snprintf(buff, 128, "{\"topic\":\"iot\"}"); I have tried to replace this with snprintf(buff, 128, "{\"" + MQTTTopic + "\":\"" + MQTTPayload + "\"}"); Which is erroring on compilation. error: cannot convert 'StringSumHelper' to 'const char*' for argument '3' to...
Arduino Forum
forum.arduino.cc › projects › programming
Printf on Arduino - #6 by david_2018 - Programming - Arduino Forum
July 24, 2021 - printf is not functionally implemented in the standard Arduino environment, see https://playground.arduino.cc/Main/Printf/ You can use sprintf() or snprintf() to put the text into a char array, then print the array.
Mbed OS
forums.mbed.com › application development
Sprintf with "X" does not left pad with "0" - Application development - Arm Mbed OS support forum
June 16, 2020 - I’m porting code from an Arduino application. The following code produces the correct char array in Arduino: char hexval[5]; int gatetime= 124; sprintf(&hexval[0], “X”, gatetime); This produces 07C which is what…
Top answer 1 of 15
1
But I can't wrap my head around what the snprintf( ) command is/does.
I don't understand what it is that you don't understand...
The xxprintf(xxstuff, "format string", arg1, arg2, ...) functions all print the contents of the format string, with a variable number of arguments that are translated …
2 of 15
0
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