Detecting COM ports??

[Mad Axeman]

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?

[Mad Axeman]

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?

[Mad Axeman]

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.  
14. NEXT
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
20. NEXT
21.  
22. END
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
38. END IF
39.  
40. CLS
41.  
42. PRINT " FATAL PROGRAMME ERROR!!"
43.  
44. PRINT " Error:"; errnum
45.  
46.