Floating Points and rounding

[Uberbots]

you can most certainly deal with floating point numbers! just be careful about typecasting, because PIC C defaults to integers.... so you have to typecast everything.

multiplying by 180/127 is not a good idea... first of all because the range on the servo is not 180... its either 160 or 210 (i forgot). multiply by the decimal... you wil run into less problems.

otherwise...

float PAN_DEGREE = (160.0f / 127.0f);
TRUE_PAN_DEGREE = (float)PAN_SERVO * PAN_DEGREE;

notice the forced decimals and the f.

[JBotAlan]

Originally Posted by Uberbots

float PAN_DEGREE = (160.0f / 180.0f);

Hmm, I use (for example):

double PAN_DEGREE = whatever

I didn't even know "float" was a data type! C is obviously not my native language; VB6 is. Which has more resolution? Forget it, I'll Google it.

I didn't know about the "f" after the numbers after, but I'd seen that at some point...can't remember where.

Thanks, I'll use some of that in my code!

JBot

[Uberbots]

Originally Posted by JBotAlan

Hmm, I use (for example):

double PAN_DEGREE = whatever

I didn't even know "float" was a data type! C is obviously not my native language; VB6 is. Which has more resolution? Forget it, I'll Google it.

I didn't know about the "f" after the numbers after, but I'd seen that at some point...can't remember where.

Thanks, I'll use some of that in my code!

JBot

ill save you the trouble- double has more resolution. but considering that a double is a 64-bit data type, i wouldn't use it all that much.

[Salik Syed]

If you are only going up to 180 i don't see why a float is really necessary??? why not just multiply by 100? it'll still get you two digit accuracy

i.e: 180.00 = 18000

as for rounding a floating point number down to four decimals... it is not too hard to do, but why would you need to do it? it's not like reducing the number of decimal points will reduce the processing time more than the cost it takes to round the number.

I think the easiest way to round to four decimals would probably be to mask off the bits of the less significant digits using "&" and a masking variable
(look up bitwise operators)


this may also be of use to u:
http://en.wikipedia.org/wiki/IEEE_754

[6600gt]

Originally Posted by Uberbots

ill save you the trouble- double has more resolution. but considering that a double is a 64-bit data type, i wouldn't use it all that much.

floats and doubles are both 32bit variables in this compiler!