I am having a bit of trouble with the floating precision of float; never thought I would need this many decimal digits of precision but today it happened! My goal, from a given float (always with four decimal digits), is to extract just the decimal part ("mantissa") as an integer. So I attempted t…

Many decimal fractions cannot be represented exactly in binary. The fix is to round the number. Try this int DecimalPart = 10000 * (Value - IntegerPart + 0.00005); Pete

Pete, This fails to do the trick because the the 0.00005 addition (to the float) has an uneven effect depending on each different float. E.g., in this case, it resulted in the last two values still being mis-extracted. el_supremo: Many decimal fractions cannot be represented exactly in binary. Th…

I'm afraid you have exhausted the accuracy of the float. It just can't tell the difference between those numbers. The binary representation just ran out of bits. The hexadecimal representation of 1234.5677 is 0x449A522B. 1234.5678 is 0x449A522B. 1234.5679 is 0x449A522C. In order to get more accura…

TanHadron: Apparently doubles are implemented as floats. Yes, which is why it is indicated on the reference page for a double. http://arduino.cc/en/Reference/Double It's how avr-gcc is implemented. giantsfan3: Pete, This fails to do the trick because the the 0.00005 addition (to the float) …

My goal, from a given float (always with four decimal digits), This is where you are going wrong. You may always be printing the value with 4 digits after the decimal point, but that does not mean that the digits are accurate or correct. You could print the value with 12 digits after the decimal…

For what it's worth, I just compiled a test program using the ChipKit board (32 bit) from Diligent. Their IDE/compiler works with every Arduino sketch I've tried, so I thought it might it might be a solution. In the test, a float is 4 bytes, a double is 4 bytes, but a long double is 8 bytes. I did a…

Yes, (across many languages) floating point arithmetic in general seems to be have 6-7 total digits of precision. I've decided to store the data into a string/char-array right at the offset, then either convert it into a long and do arithmetic with it, or else directly store as a string.

Or, you could give this a spin... [image] Arbitrary precision (big number) library port for Arduino Programming I love big numbers ... they are so ... big! So in the spirit of getting your Arduino to handle nice, big, numbers I have ported (with pretty minimal effort on m…

Since the microcontroller treats every number as a binary integer and merely fakes floating point, you can do the same. You should simply avoid floating point entirely.

[quote author=joe mcd link=topic=170633.msg1270879#msg1270879 date=1370699821] Since the microcontroller treats every number as a binary integer and merely fakes floating point, you can do the same. You should simply avoid floating point entirely. [/quote]ehhrrr? Any and every computer treats eve…

Extracting just the decimal part of a float

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Coding_Badly June 8, 2013, 3:00am 9

Or, you could give this a spin...

Old link: http://forum.arduino.cc/index.php?topic=85692.0

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Extracting just the decimal part of a float

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