PbPro Maths Help

[Acetronics2]

I'm a real PbPro Maths dunce ...

Baiscally i have a byte array of hex data BD[11] recieved via a serial interface. I'm happy with this and the data recd.

Now taking bytes from array BD [4] and BD [5] as an example i need to perform the following calcu
lation on the bytes.



I appreciate the decimal point will cause an issue. Any examples of code that would perform this.

I came up with

Result = (((BD[4] * 128) + BD[5]) - 2048) / 20.48

But this losses the accuracy of the end part of the formula?

...

Also for a second formula involving BD [2] & BD [3] I need to

I'm stuck on extracting a value for the right hand digit of the hex number?

Hi,

1) Result = (((BD[4] * 128) + BD[5]) - 2048) / 20.48

lets write it ...

20.48 = 512 /25 ... ; 2048 = 100 * 20.48 ...

result = ((((BD[4] << 7) + BD[5] ) * 25) >> 9) - 100

not so good as a calculation ... don't you have a better formula ???
( BTW... I'm curious to see your project ...)

BD[5] obviously is a word ( or smaller !!! ) ... so, at least, its 4 lower digits are lost in the calculation ...


2) It's a typical "masking" job ... ( I suppose it's a HEX digit, you look for ? ) ...

so, you could use ...

Ldigit = Res & $000F( for a Word )

Ldigit = Res & $0000000F ( for a LONG )


Alain