Month: July 2025

I cleaned up the library reference, inserted a table of contents and organized the reference in a slightly different way: All the conversion functions are now grouped together towards the end of the reference. Additionally, links between the documentation of the functional groups and the library reference were installed. All this shold it make easier to quickly find the functions needed.

Due to some questions regarding sin(pi), an article is available explaing the problems of floating point math: fp64_sin(float64_NUMBER_PI) is not 0.

A lot of microcomputer applications display data of sensors or calculations over a bigger range, e.g. voltages from millivolts to volts or resistors from ohm to kiloohm to megaohm. Usually, data is then displayed in engineering format, which is similar to scientific notation, but the exponent is always a multiple of 3 (e.g. 12.345E3 instead of 1.2345E4).

A new function, fp64_etoa is available for this use case. It has the exact same parameters as fp64_ftoa, making code changes easy. Application could even offer the user the possibility to switch between the scientific notation and engineering notation by using fp64_ftoa or fp64_etoa respectively.

V1.1.25 also fixed a bug in fp64_ftoa, that occured only on the MEGA 256 processors like on the Arduino Mega board.

fp64_to_decimalExp now returns the specified number of decimal digits instead of just “0”.

E.g., fp64_to_decimalExp(x,4,false,NULL) will return “0.000E0” instead of “0“.

With that change, behaviour is now consistent for all finite numbers, but it will be no longer consistent with the the previous 64-bit C-library avr_f64.c.