Using RxCheck

Comments

• kuroneko Posts: 3,623

  2014-03-23 16:27 edited 2014-03-23 16:27

  rxcheck returns -1 or the first available character.

  if (comd := USB.rxcheck) <> -1
      ' do something
  
• Duane Degn Posts: 10,588

  2014-03-23 16:29 edited 2014-03-23 16:29

  Which object are you using?
  
  In many objects rxCheck returns -1 is no character is received but if there is a character it will be returned. So do something like:
  

  result := USB.rxCheck
    if result <> -1
      ' do something with character stored in result.
  
• Duane Degn Posts: 10,588

  2014-03-23 16:30 edited 2014-03-23 16:30

  kuroneko wrote: »

  rxcheck returns -1 or the first available character.

  if (comd := USB.rxcheck) <> -1
      ' do something
  

  
  "comd" needs to be a long, right?
• kuroneko Posts: 3,623

  2014-03-23 16:39 edited 2014-03-23 16:39

  Duane Degn wrote: »

  "comd" needs to be a long, right?

  Only when you assign first and then do the comparison. Doing it in one go can take any type (width cut-off doesn't affect comparison).
• Duane Degn Posts: 10,588

  2014-03-23 16:43 edited 2014-03-23 16:43

  kuroneko wrote: »

  Only when you assign first and then do the comparison. Doing it in one go can take any type (width cut-off doesn't affect comparison).

  
  Thank you kuroneko.
  
  That's just want I wanted to know. I didn't know one could do it that way.
• steprog Posts: 227

  2014-03-23 17:17 edited 2014-03-23 17:17

  That seemed to work thanks, but I still don't understand why I couldn't use it as a boolean expression and test it for true or false
• kuroneko Posts: 3,623

  2014-03-23 17:53 edited 2014-03-23 17:53

  steprog wrote: »

  ... but I still don't understand why I couldn't use it as a boolean expression and test it for true or false

  The returned values include $00..$FF (the actual character) and $FFFFFFFF (no character). This is not a TRUE/FALSE API. If you want that you'd need to introduce your own method which simply returns the rx fill level, then you can simply fetch a character (after doing a boolean check).
• Peter Jakacki Posts: 10,193

  2014-03-23 18:14 edited 2014-03-23 18:14

  Since the IF statement really only looks for a false or non-false I simplify it like this:
  ch := coms.rxcheck
  if ch+1 ' a -1 becomes 0 or false
  ' do something
  
  but in this case ch was declared as a local variable so I guess it works because it is a long