Troubleshooting an RS-232 Interface Problem
It is somewhat of a challenge to diagnose a communications problem between an X-Rite instrument and the personal computer. Trouble may reside in one or more of three places; [1] the instrument, [2] cable, or [3] PC. The list below illustrates SOME of what might be wrong.[1] Instrument -
- Broken? Has it ever worked before? Before giving up hope, read on.
- Misconfigured? If it is not factory new, out-of-the-box, consider resetting the unit. From the home page of the Support section, use the search the knowledgebase using "resetting" as keyword. Ensure that you have also selected the appropriate product line!
[2] Cable -
- Correct for the task? Verify that the cable is listed in our interface cabling matrix - - see related link to the left.
- Bad connection or broken wire? Unless there is a spare on hand this is hard to prove. Has it worked before? Is it properly attached?
[3] PC-
- Correct port selected? Many PC's have more than one RS232 (A.K.A. Com or COMM) ports. In the X-Rite software application, the user must select the port to which the instrument is attached. Failure to select the appropriate port results in communications errors. Do not be shy about trying everything in the list. Selecting an incorrect port will do NO damage. Start with Com1 and work through the list.
-
Cable attached to selected serial port? Most PC's will utilize one of the two following physical communications ports!
9-pin male (A.K.A. DB9p)
or
25-pin male (A.K.A. DB25p)On many machines, these ports are not clearly marked! Thus it is quite easy to assume and be wrong in the assumption. As with the preceding item, do not be shy about moving the cable from one port to another, This will NOT damage PC or instrument.
Finally be aware: Almost all PC's are equipped with a Centronics PARALLEL port. This port is ALWAYS a 25-pin FEMALE! Feel free to attach a printer here - but NOT an instrument. The vast majority of X-Rite instruments are SERIAL not PARALLEL! - Port enabled by the system or BIOS? Recently PC's have been seen where the physical ports exist but they are turned off. IBM laptops (Model 380 for example) are delivered with an Infrared port enabled and all serial ports disabled. It takes a bit of playing to bring these PC's online. Other vendors have also been observed to ship their hardware with the serial ports disabled in BIOS. It is far beyond the scope of this document to explore the hundreds of BIOS variants. Where everything else has failed, get the Information Services team to assist. BIOS is no place to go unless you are well skilled in PC maintenance. A bad choice here CAN leave a non-functional PC behind.
- Port NOT in use by some other device? Palm Pilots have increased the number of interface calls significantly! These and other SERIAL devices abound in the real PC world. By design however, a PC can have one-and-only-one device (or software application) attempting to use each serial port. Where two such instruments or programs exist, there will be trouble. It is always a good idea to shut down, turn off, disable, any and all other applications when attempting to troubleshoot a communications issue. Do not be surprised if the little label printer, the palm pilot, the ink dispenser interface, the internal modem, or some other seemingly unrelated machinery is at the heart of the problem. Start simple and work up to complex.
