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BobD

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Joined: 07/12/2011
Location: Australia
Posts: 935

Posted: 10:34pm 23 Feb 2012

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When I build a menu I like to use a single keystroke entry without the need for a <CR>. In my thinking it leads to a clean UI. So I have been using INKEY$ as the means of getting the keystrokes. While doing that I ran across some difficulties. The following code does not work. All I get is the loop exits but I get null values presented.

? " Tell me what to do"
do
loop until inkey$ <> ""
k=val(inkey$)
on k gosub dummy, dummy, dummy, dummy, dummy, dummy, dummy, dummy, dummy

After some experimentation I have this code which works.

? " Tell me what to do > ";
Do
k$=Inkey$
Loop Until k$ <> ""
k=Val(k$)
On k GoSub dummy, dummy, dummy, dummy, dummy, dummy, dummy, dummy, dummy

Ignore the "gosub dummy". I build my front end first and then as I finish the work modules I then include access to them, in this case via the "on k gosub". Until it is all finished I have a subroutine named Dummy: which does nothing but return.

My conclusion is that INKEY$ only has a valid value until the first access after it is set and if you want to continue use of that value then it has to be saved as in "k=val(inkey$)". Is this correct?

Are there any other variables that may work similar? MM.I2C may be another one but I haven't tried it.

bigmik

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Joined: 20/06/2011
Location: Australia
Posts: 2946

Posted: 10:39pm 23 Feb 2012

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BobD said

My conclusion is that INKEY$ only has a valid value until the first access after it is set and if you want to continue use of that value then it has to be saved as in "k=val(inkey$)". Is this correct?

Hi Bob,

I think your synapses is correct. You are basically doing TWO Inkey$ tests the first one exits your loop and the second one returns a NULL so doesnt work.

It is standard practise to assign a variable to the Inkey$ read and then test it as you have done in your second example.

Regards,

Mick

Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<

djuqa

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Joined: 23/11/2011
Location: Australia
Posts: 447

Posted: 11:44pm 23 Feb 2012

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Inkey$ is a Pseudo-variable.
It obtains the current keypress value each time it is used.
Therefore as BIGMIK stated you need to assign the value to a variable to allow you to use it in the manner you wish.

VK4MU MicroController Units

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