Doing Simple Math - getting the wrong answer

[anj]

First - theBase # is "223" This is the value in #Dec_temp

Then look at the math:
Testmath1 - (Dec_temp*(9/5)+32) = 255 -- this is wrong

PBP uses full precedence of math operators, and also uses braces to force out of order of calculation.
Secondly it also only works in integers.

As such (9/5) = 1.8 = 1 ( and is calculated first )
hence Dec_tempf = 223 * 1 +32 = 255

try ( Dec_temp*( 90 / 5 ) + 320 ) / 10
ie ( Dec_temp*18 + 320 ) / 10

Also, if you just leave it at ( Dec_temp*18 + 320 ) you can use simple math to get the basic temp and the first decimal.

Andrew

[Ingvar]

Hi Tom,

PBP can't handle fractions very well, the "**" and "*/" operators however makes it possible. 9/5 is 1.8 which PBP will trunctate to 1, not very useful. The "**" operator can handle the fractional part, this operaton makes an "invisible" division by 65536. 0.8*65536=52428.8 which we round up to 52429. Since your Dec_temp variable contains the temerature in tenths of a degree your formula needs to be ......

Dec_tempf=Dec_temp*(9/5) + 320 'Farenheit * 10

We rewrite this to ...
Dec_tempf=Dec_temp*1.8 + 320 'Farenheit * 10

Which is the same as .....
Dec_tempf=Dec_temp*1+Dec_temp*0.8 + 320 'Farenheit * 10

Using "**", we end up with ......
Dec_tempf=Dec_temp + Dec_temp**52429 + 320

Another thing, you can replace ......

' read data for temperature Temp
SSD4= (ssmax[24]>>4)
SSD3= (ssmax[24] & $f)
SSD2= (ssmax[23]>>4)
SSD1= (ssmax[23] & $f)

' convert to Decimal:

Dec_temp=(ssd4*4096)+(ssd3*256)+(ssd2*16)+ssd1

...... with ......

Dec_temp.highbyte = ssmax[24]
Dec_temp.lowbyte = ssmax[23]

/Ingvar

[Luciano]

Fahrenheit = Celsius * (212 - 32)/100 + 32


Example 30 Celsius to Fahrenheit:


30 * 180 / 100 + 32 = 86 Fahrenheit


Best regards,

Luciano