Help with phsa

Andrew C

Hi,
When I put this code into my program:

time := (phsa - 624) #> 0···············
a := time

the time variable will·display a number like 773 in hyper terminal.

However, when I display a, it will show a number such at 1e-42.

Can someone please explain to me why a does not read the same as time?

Rayman

I think you need to say exactly how you are outputting those vars to hyperterminal...

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Andrew C

Gah,
I need to put a filter on my thinking. Yep, I converted to string!

Rayman

Hmm... Are a and time both longs? I would think either a and time are different types or something is horribly wrong!
What are you using to convert to string?

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Andrew C

The b variable reads 1108384835 and never changes, although I have it set up to a variable resistor on pin 17
a is multiplying ok, but it appears to be the "b" that is not adding correctly.

Strange, here is the code:


long a
long b
long c
long time


dira[noparse][[/noparse]17] := outa[noparse][[/noparse]17] := 1
waitcnt(clkfreq/10_000 + cnt)
phsa~
dira[noparse][[/noparse]17]~
waitcnt(clkfreq + cnt)
time := (phsa - 624) #> 0
Debug.Str(String(13, "time = "))
debug.dec(time)
Debug.Str(String(" which correlates to "))
a := fMath.FMul(time, 1.5279)
b := fMath.FAdd(a, 36.1526)
debug.dec(b)
Debug.Str(String(" ohms"))
Debug.Str(String(13, "a = "))
Debug.dec(a)
Debug.Str(String(13, "b = "))
Debug.dec(b)
Debug.Str(String(13, "c = "))
Debug.dec(c)
Debug.Str(String(13, "Dec version of time = "))
Debug.dec(time)
Debug.Str(String(13, "Dec version of a = "))
Debug.dec(a)
waitcnt(clkfreq + cnt)

Post Edited (Andrew C) : 12/16/2009 12:11:08 AM GMT

Rayman

Ok, you need someone who has used floating point with the Prop before (not me)!

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Andrew C

@ Rayman, Thanks for trying!

Graham Stabler

Within the floatmath object there is a function to convert integers to floats, this will be needed to convert phsa so it makes sense within floating point mathematics I think.

In the floatstring object there is a function to convert a float to a string which would be useful when outputting to the terminal.

There is a float demo showing the use of floatstring that comes with the prop tool.

Cheers,

Graham

p.s. to make your code more readable surround it with code tags [noparse][[/noparse]code ] and [noparse][[/noparse]/code ]

(but remove the spaces between the square brackets)

Andrew C

@Graham,

Thank you! I'm learning more again. Here is the code I used to help understand:

'' File: 1Test.spin

OBJ

   fM: "Float32"             ' Use floating math routines
   p: "FullDuplexSerialPlus" ' Use with Parallax Serial Terminal
   fS: "FloatString"         ' Use floating math to String routines

CON
   _clkmode = xtal1 + pll16x ' System clock → 80 MHz
   _xinfreq = 5_000_000

VAR
   long num1
   long num2
   long x
   long y


Pub Init

   p.Start(31, 30, 0, 9600)       ' Initialize the serial terminal
   fM.start                       ' Initialize the floating point math in a cog
   waitcnt(clkfreq * 3 + cnt)     ' Wait 3 seconds to press "Enable" on Serial Terminal

   main                           ' start the main program

PUB main


   p.str(string(16))              ' Clear the terminal screen 
   p.str(string("Begin output", 13))
   num1 := clkfreq
   p.dec(num1)
   p.str(string(13))              ' CR/LF

   'x := 1.1                      'Begin output
   'y := 2.2                      '80000000
   'num2 := x * y                 '-259040215 (because variables are fp)
   'p.dec(num2)                   'End output

   'x := fM.ffloat(1.1)           'Begin output
   'y := fM.ffloat(2.2)           '80000000
   'num2 := fM.FMul(x, y)         '1568564747 (because answer is in fp)
   'p.dec(num2)                   'End output

   'x := 1.1                      'Begin output
   'y := 2.2                      '80000000
   'num2 := fM.FMul(x, y)         '1568564747 (because answer is in fp)
   'p.dec(num2)                   'End output

   x := 1.1                       'Begin output
   y := 2.2                       '80000000
   num2 := fM.FMul(x, y)          '2.42 (correct)
   p.str(fS.FloatToString(num2))  'End output (needs to convert answer to fp)

   p.str(string(13))

   x := 2
   y := 3
   num2 := x * y
   p.dec(num2)                    'displays "6" correct (because answer is integer)

   p.str(string(13))

   'x := 1.1                             'Begin output
   'y := 2.2                             '80000000
   'num2 := fM.FMul(num1, 1.0)           '2.42             (correct)
   'p.str(fS.FloatToString(num2))        '6                (correct)
                                         '4.624469e-36     (because num1 is integer)

   x := 1.1                              'Begin output
   y := 2.2                              '80000000
   num2 := fM.FMul(fM.FFloat(num1), 2.0) '2.42            (correct)
   p.str(fS.FloatToString(num2))         '6               (correct)
                                         '160000000       (correct - converted num1 to float before multiplying)
   
   p.str(string(13,"End output"))

Post Edited (Andrew C) : 12/16/2009 2:49:19 AM GMT