Best way to us atan or atan2

electric550

Is there a math library that allows for use of integers for the atan2 math function. The only math library that I can find that supports atan2 uses floating point. The problem is that I am getting data then I want to use the atan2 method and send out the value in degrees from the serial port but the value is in floating point so when I send the data out the serial port using the decimal format the result is a large number because of the formating. Thanks!

electric550

I was looking for a short function with lookup table of some sort perhaps, to speed things up. I could write one but I just wanted to see if there was a quick way to do this all ready written.

Timmoore

This thread talks about an int math lib http://forums.parallax.com/forums/default.aspx?f=25&m=371538 but it doesn't loko like its ready.
There are a couple of other options - multiple the float by 100 and convert to int and send that, it gives you a 2 deciaml place number - you can do it to other no of places as well.
Look at FloatString.spin it allows to to convert a float to a string and control the format - no of places etc.

electric550

I tried to do the following but it is returning a zero
when the code runs an example of the two variables would be X = 315 Y = -375

On my calculator this returns -0.6986 in radians so multiply by 180/pi = -40.030 but here it is just outputing zero.
Is it posible to use these two libraries together or is this a problem?


math : "DynamicMathLib"
floatm : "FloatMath"


Z := math.ATan2(X,Y)
Z := Z*180/3.14159
Z := floatm.FRound(Z)
uarts.dec(0,Z)

electric550

I will take a look at that

electric550

Well that did not work maybe I am doing something wrong I tried

FloatString : "FloatString"
math : "DynamicMathLib"

Z := X/Y
Z := math.ATan(Z)
Z := Z*180/3.14159
Z := FloatString.FloatToString(Z)
uarts.str(0,Z)
uarts.tx(0,10)
uarts.tx(0,13)

here is some data that si returned

Mag XYZ: 47 -525 -673
1.401298e-45
Mag XYZ: 48 -528 -671
1.401298e-45
Mag XYZ: 52 -527 -669
1.401298e-45
Mag XYZ: 54 -535 -672
1.401298e-45
Mag XYZ: 58 -531 -669
1.401298e-45

It always returns either the small number shown above or 0 depending on orientation. So I am not sure what is going on at this point. I will look for something silly.

Timmoore

Are X and Y floats? THe float libs will only take floats. Also the Z := Z*180/3.14159 is incorrect, you need to use float routines for * and /
e.g. Z:= math.FMul(math.FDiv(180,3.14159))
This also works (from some of my code - looks like its doing similar)

     a2tan_angle[noparse][[/noparse]Pitch] := fMath.FMul(t.ATan2(tiltReadings[noparse][[/noparse]tyAxis], tiltReadings[noparse][[/noparse]tzAxis]), constant(180.0 / pi)) 'use accelerometer to calculate pitch tilt    

electric550

Yea you are right that fixed it...Thanks A bunch! i did not realize that the float and ints were like that...Thanks again.