multiplication and division with pbp

[klemm]

Hello,

how I can write this formula in pbp:

volt = INT(5.0/1024*volt1*1000)

Thanks

Klemm

 

[ME]

I don't know much about Basic, but it's usally better to right shift than divide, especially when you divide by a power of 2. Shifting is not as demanding a task as division. 1024 is the same as 2^10 so instead of division by 1024 you should right shift 10 times.
You should also do all multiplications before division, to minimize rounding errors.
In C it would look something like this:

volt=((5*1000*volt1)>>10);

or simpler:
volt=((5000*volt1)>>10);

 

[C-Man]

First I must say that I know nothing about PBP ...

I assume you want to calculate the voltage from a value measured by a 10 bit Pic DAC ??

If PBP has a datatype that can at least hold 640000 (that uses 3 bytes) I would do it like this:

volt=(volt1*625)/128

A division by 128 could be done as a shift of the value 7 bits to the right, no idea if PBP can do this.

Just a short note: you will never reach the value of 5000 as the maximum value you get from the DAC is 1023 (or 0x3FF) ...

best regards

 

[Tornado]

Yes PBP supports SHIFT consult the manual.
Tornado

 

[ME]

Then the best way would be to do like this:

volt=((625*volt1)>>7);

This is C language.
>>7 menas right shift 7 times.
I don't know how to write this in BASIC, but maybe you can figure this out yourself.