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Active Forums => QB64 Discussion => Topic started by: Mad Axeman on November 08, 2020, 07:24:52 am

Title: Detecting COM ports??
Post by: Mad Axeman on November 08, 2020, 07:24:52 am
I've written a program that reads data from the RS-232 port on an instrument via a USB - RS-232 adapter. At the moment I have a prompt for the user to input the COM port that the adapter is using. Is there a (simple) way to detect what COM ports are in use so that I can put them in a pull down menu for the user to pick?
Title: Re: Detecting COM ports??
Post by: Mad Axeman on November 08, 2020, 08:41:43 am
My current workaround is to use an array for the ports. I then use a 'for x to y' loop to open each COM port in turn. If it brings up an error '68' then  stick a '0' in the array corresponding to that port number. If it doesn't return error '68' then that port is answering and stick a '1' in the array for that port. My pull down list will just include array entries that are '1'.

Must be a simpler way?
Title: Re: Detecting COM ports??
Post by: Mad Axeman on November 08, 2020, 10:16:09 am
My current way of doing things. Any suggestions for an easier way? Not the neatest code but that's the way I do things :-)
Code: QB64: [Select]
  1. DIM ps(255) AS INTEGER
  2. ON ERROR GOTO fault
  3.  
  4. 'create a loop that opens comm 1 to comm 255 in turn
  5. FOR i = 1 TO 255
  6.     port$ = LTRIM$(STR$(i))
  7.     re = 1 ' This sets up the return from the error trap
  8.     o = 1 ' Set this to 1. If it's not open then it sets this to 0
  9.     CLOSE 1 ' Make sure port is closed before we try to open it
  10.  
  11.     OPEN "COM" + port$ + ":9600,N,8,1,BIN,CS0,DS0" FOR RANDOM AS #1 ' try and open the port
  12.     ps%(i) = o ' Set ps%(i) to 1 for openable or 0 if not
  13.  
  15.  
  16. ' Display which ones are openable
  17. PRINT "The following ports are openable"
  18. FOR i = 1 TO 255
  19.     IF ps%(i) = 1 THEN PRINT i
  21.  
  23.  
  24.  
  25. ' Catch the error
  26. fault:
  27. errnum = ERR
  28.  
  29.  
  30. ' why re = 1
  31. ' Well, at a point later in the main program I open the comm port again.
  32. ' That time re will be 0 so it won't go to the RESUME NEXT,
  33. ' it will go to a second IF (errnum = 68) THEN error call
  34. IF (errnum = 68 AND re = 1) THEN
  35.     o = 0
  36.     CLOSE 1
  37.     RESUME NEXT
  39.  
  41.  
  42. PRINT " FATAL PROGRAMME ERROR!!"
  43.  
  44. PRINT " Error:"; errnum
  45.  
  46.  
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