Logarithm in PBP

[savnik]

I use this code to read the forwardpower

    ADCIN 0, adval	                ' Read channel 0 to adval
    dummy = adval * 5 * 10          ' Multiply to load internal registers with 32-bit value
    value = Div32 1023              ' Divide 32-bit value by word and store in word    
    forwardpower = (value*value)/50

and this for reflected power

    ADCIN 1, adval1	                ' Read channel 0 to adval
    dummy1 = adval1 * 5 * 10        ' Multiply to load internal registers with 32-bit value
    value1 = Div32 1023             ' Divide 32-bit value by word and store in word    
    reflectedpower = (value1*value1)/50

and the type for SWR is:

..........1 + square root(reflectedpower/forwardpower)
SWR = --------------------------------------------
..........1 - square root(reflectedpower/forwardpower)

Any help how to show the SWR on LCD;

[paul borgmeier]

The largest ADVAL1 can be is 1023
The largest dummy can be is 1023 * 5 * 10 = 51150 (which is 16 bits or less)

Why do you do the * 5 * 10, why not * 50? and why *50?
You do not need DIV32 since you never exceed 16 bits with dummy

The same goes for ADVAL calcs

In final form, your
RP = (ADVAL1*50/1023)^2/50
FP = (ADVAL*50/1023)^2/50

If you plug these into your SWR equation and reduce, you get

SWR = (ADVAL1+ADVAL)/(ADVAL1-ADVAL), which should be easy to deal with

However, with all this noted, I do not think you are going to get what you want ... or will you? I haven't yet tried to follow this thread in any depth.

[savnik]

The largest ADVAL1 can be is 1023
The largest dummy can be is 1023 * 5 * 10 = 51150 (which is 16 bits or less)

Why do you do the * 5 * 10, why not * 50? and why *50?
You do not need DIV32 since you never exceed 16 bits with dummy

The same goes for ADVAL calcs

In final form, your
RP = (ADVAL1*50/1023)^2/50
FP = (ADVAL*50/1023)^2/50

If you plug these into your SWR equation and reduce, you get

SWR = (ADVAL1+ADVAL)/(ADVAL1-ADVAL), which should be easy to deal with

However, with all this noted, I do not think you are going to get what you want ... or will you? I haven't yet tried to follow this thread in any depth.

I use adval * 5 * 10 , because adval * 5 is to show on lcd
the volts from 0 to 5v and 10 is multiplier to show on lcd 0 to 50v