FSX Incrementing active frequency

[dnauk]

Hi Folks,

Having cracked the functionality of my RNAV, I am now reproducing the functionality of my Narco panel COM radios - these have a toggle switch enabling the pilot to change the active frequency rather than standby frequency. I have reproduced this but the quarter frequencies do not increment correctly.

I am effecting this by adding 0.025 decimal to the saved value of COM1 ACTIVE FREQUENCY

The functionality is there but the problem I am seeing is that XXX.X5 can end up as XXX.X6 and sometimes instead of XXX.X7 or XXX.X8 I can get XXX.X9 My guess is that this is becasuse FS stores quarter frequencies as BCD which effectively is a rounded second decimal place (but could be variously rounded up or down) and therefore when I add 0.025 XXX.X3 I get XXX.X55 which can then be rounded to XXX.X6 and so on. Setting the active frequency with the K:COM_RADIO_SET accepts the wrong value.

I rather assume that there is an elegant way of doing it with BCD maths (which I don't yet understand well). Any tips would be much appreciated.

Macros I am using are:

<Macro id="ConvertFrq" Name="ConvertFrq">
(L:COM1 ACTIVE FREQUENCY,MHz) 100 * near 10000 % d 10 % r 10 / int d 10 % r 10 / int d 10 % r 10 / int 16 * + 16 * + 16 * +
</Macro>

and

<Macro id="DecLarge" Name="DecLarge">
(A:COM1 ACTIVE FREQUENCY, MHz) 119 &lt;
if{ 136 (A:COM1 ACTIVE FREQUENCY, MHz) 118 - + (&gt;L:COM1 ACTIVE FREQUENCY,MHz) }
els{ (A:COM1 ACTIVE FREQUENCY, MHz) 1 - (&gt;L:COM1 ACTIVE FREQUENCY,MHz) }
@ConvertFrq
</Macro>

<Macro id="DecSmall" Name="DecSmall">
(A:COM1 ACTIVE FREQUENCY, MHz) 118.5 &lt;
if{ 136.975 (&gt;L:COM1 ACTIVE FREQUENCY,MHz) }
els{ (A:COM1 ACTIVE FREQUENCY, MHz) 0.025 - (&gt;L:COM1 ACTIVE FREQUENCY,MHz) }
@ConvertFrq
</Macro>

The outputs are then set using (&gt;K:COM_RADIO_SET)

 

[taguilo]

I rather assume that there is an elegant way of doing it with BCD maths (which I don't yet understand well). Any tips would be much appreciated.

Yes, there is an elegant way, and besides it lets you save a bit of code:

Instead of:

<Macro id="ConvertFrq" Name="ConvertFrq">
	(L:COM1 ACTIVE FREQUENCY,MHz) 100 * near 10000 % d 10 % r 10 / int d 10 % r 10 / int d 10 % r 10 / int 16 * + 16 * + 16 * + 
</Macro>

Use:

 <Macro id="ConvertFrq" Name="ConvertFrq">
	(L:COM1 ACTIVE FREQUENCY,Frequency BCD16) 
</Macro>

And that's it.

Tom

 

[tedcook]

I have used:-
(>K:COM_RADIO_WHOLE_INC) and (>K:COM_RADIO_WHOLE_DEC)

(>K:COM_RADIO_FRACT_INC) and (>K:COM_RADIO_FRACT_DEC)

these roll over at the end of the range.

Ted.

 

[dnauk]

Clarification

Hi Tom & Ted

Tom:- the macro "ConvertFrq" is not the problem, the problem is incrementing the active frequency. However, are you saying that

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + (&gt;L:COM1 ACTIVE FREQUENCY,Frequency BCD16)

will work reliably where

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + (&gt;L:COM1 ACTIVE FREQUENCY,MHz)

doesn't?

Ted, I AM using K:COM_RADIO_WHOLE_INC etc when the STANDBY frequency is being changed but this does not work on ACTIVE frequencies - I am trying to reproduce the full functionality of the Narco COM 810 radio which gives the pilot the option, by flicking a switch on the radio of tuning the standby frequency OR tuning THE ACTIVE FREQUENCY DIRECTLY.

SO I am effectively trying to create equivalents of:-
K:COM_RADIO_ACTIVE_WHOLE_INC K:COM_RADIO_ACTIVE_WHOLE_DEC
K:COM_RADIO_ACTIVE_FRACT_INC K:COM_RADIO_ACTIVE_FRACT_DEC

My macros IncLarge, IncSmall, DecLarge, DecSmall are attempting to do this, but as I say they aren't working quite right.

 

[taguilo]

Tom:- the macro "ConvertFrq" is not the problem, the problem is incrementing the active frequency. However, are you saying that

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + (&gt;L:COM1 ACTIVE FREQUENCY,Frequency BCD16)

will work reliably where

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + (&gt;L:COM1 ACTIVE FREQUENCY,MHz)

doesn't?

There are two aspects you must take into account when converting numbers into frequencies using K:COM_RADIO_SET

1) That big conversion formula is not really needed because you can let an LVar's internal conversion do the job.

Now, this is wrong:

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + (&gt;L:COM1 ACTIVE FREQUENCY,Frequency BCD16)

because you are assigning a Mhz unit-value to a Frequency BCD16 unit-value, giving an unpredictable result.
What you need to do is first assign the value to its typical display unit -Mhz in this case, and then store in the stack the same variable, but with the proper unit -Frequency BCD16 that will be accepted by the event:

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + (>L:COM1 ACTIVE FREQUENCY, MHz) (L:COM1 ACTIVE FREQUENCY,Frequency BCD16) (>K:COM_RADIO_SET)


2) When displaying a COM value obtained with this method, you must pay attention to possible formatting issues. It is not the same to show a frequency with 2 decimal places than to show it with 3, because of a rounding factor.When using 2 decimals, writing %((A:COM1 Active Frequency,Mhz) 0.00001 +)%!3.2f! will do the trick.

Besides,when adding or substracting values to the frequency, a floating point factor must be considered as well.
For example, in a subtraction:

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 - 0.00001 + (>L:COM1 ACTIVE FREQUENCY,MHz)
(L:COM1 ACTIVE FREQUENCY,Frequency BCD16) (>K:COM_RADIO_SET)

The factor correction in red will avoid a floating point offset that could show at some point(s) of the range

And the same for an addition:

(A:COM1 ACTIVE FREQUENCY, MHz) 0.025 + 0.00001 + (>L:COM1 ACTIVE FREQUENCY,MHz)
(L:COM1 ACTIVE FREQUENCY,Frequency BCD16) (>K:COM_RADIO_SET)


Hope this helps,

Tom

 

[dnauk]

Factor correction

Hi Tom, many thanks - the factor correction was the key. Next job is to develop the Narco HSI 100. Thanks again.