floatToString

Library for converting float values to strings

This library provides a C code function named floatToString() that converts a float (floating point) value to a string with specified number digits after the decimal point. It rounds the value to the nearest least significant digit. This library makes it easy to print floating point values to a serial port or to a device.

Usage

Here is sample code showing how to use the floatToString() function. It also uses the monitor_printf library to printf to the serial monitor window.

#include <floatToString.h>
#include <monitor_printf.h>

void setup() {
  monitor.begin(&Serial, 115200);
  for (int digitsAfterDP = -1; digitsAfterDP <= 6; digitsAfterDP++) {
    char S[15];
    float pi = 3.141592654;
    floatToString(pi, S, sizeof(S), digitsAfterDP)
    monitor.printf("Pi is %s (rounded to %d digits after the decimal point)\n",
      S, digitsAfterDP);
  }
}

void loop() {
  delay(100);
}

The floatToString() function has this declaration:

char* floatToString(float f, char* S, size_t n, int digitsAfterDP);

The argument f is the float value to convert to a string, S is a character buffer big enough to hold the result, n is simply sizeof(S), and digitsAfterDP is the number of digits you want after the decimal place. It can be 0 for no digits after the dp, and it can even be negative. For example, -2 means that the last two digits just left of the decimal point are to be 0 after rounding the next digit up (and the number must be at >99 or < -99).

The function returns the value of S, which allows a call to the function to be used as an argument to a function, such as for a printf %s-specifier's value.

Note: In many architectures, a float value is a 4-byte value with a 23-bit mantissa, which is good for accurately representing 5 to 6 significant digits.

Contact

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You can contact me (the author) at ted@tedtoal.net