RS232 - Debugging WBo2 - PC connections

Symptoms of bad communications between PC and wideband unit include not being able to use logging software ("Unable to connect" messages, etc.) or Tech Edge utility software where the status indicator goes red instead of green. The actual problem can be broken into 4 main areas.

  1. PC serial port problem:. You need a functioning RS232 port (with DB9 connector). If you have just a USB port, then you'll need a USB to RS232 adaptor. Most current USB-RS232 adaptors are quite reliable, but avoid trying to use an older adaptor as some early ones had firmware bugs. The easiest way to simply check a USB adaptor is a simple RS232 loop-back test (described below) that uses a communications program (Like Hyperterminal) to get a typed character to be echoed back on the screen.

  2. Software setup problem: Ensure you have followed the instructions to use the software! Tech Edge software has a "traffic light" indicator that shows green when successful communication starts with a WBo2 unit. The green indication is not a reliable indication of a good quality connection. More information can be found in the relevant software section.

  3. DB9 to RJ45 adaptor problems: The Tech Edge supplied adaptor cable is usually very reliable unless physically damaged. Some of these cables were quite short, and other much longer. First check for any obvious physical damage, and either repair or replace as appropriate. See the tips to check, debug, and fix it, below.

  4. WBo2 RS232 problems: Diagnostic steps so solve simple problems are covered below. Often RS232 problems are caused by the RS232 driver chip (an ST202) getting zapped, but other WBo2 problems can cause similar symptoms. Your WBo2 unit's diagnostic LEDs don't show RS232 faults, but if the WBo2 unit is not correctly going through its normal warmup sequence (20-30 seconds to heat the sensor to operating temp) then the problem may be more fundamental than an RS232 problem. In these cases sometimes a rescue re-flash can reload the on-board firmware to restore operation - but a potential Catch-22 situation arises here in that the rescue-reflash will only work if the RS232 is correctly working.

Debugging DB9 to RJ45 cables - Loop-back Test

The schematic at right is for the DB9 to RJ45 adaptor cable used on WBo2 units starting with version 2. Note that although the WBo2 unit uses an RJ45 connector, the port is not compatible with Ethernet networks and is simply a convenient and readily available multi point connector we use.

Follow this procedure to find where "RS232 is broken"

  • A. We recommend you use one of the Tech Edge utilities like wbCONF. You should download wbCONF, read the documentation for it, and run it. Firstly remember that the COM ports it allows you to select are COM ports not being used by other programs. If another application has "grabbed" the COM port you should be using, then you'll have to close that other program. You then should be able to select the COM port you need to use. If you're unsure of the COM port you'll have to try them one by one as follows.
  • B. Select the COM port to try from wbCONF's drop down menu. Use a screwdriver to short between pins 2 and 3 of the DB9 that is the COM port on your PC (see image). If you type characters into the Command box (say you type xx and then press the Enter key, you should see the typed characters echoed. You should see the characters you just typed. If you uncheck the [History]? checkbox then this should become clearer. Remember that you should NOT also short pins 2 & 3 to the metal shell of the DB9 as this may short the drive signal to GND. It may be easier, if you have a spare unsoldered DB9 female connector - plug it into the COM port (male) DB9 connector and then it easier to short pins 2 & 3 together and there is no metal surround.
  • C. When you get characters echoing then you know your PC's COM port is working at the most basic level - go to F below. Some other points to note are that you do NOT have to set the COM port parameters under your operating system as wbCONF sets them on-the-fly. If you do not have male pins on the DB9 (but rather female socket holes), then you may be using the wrong connector - some PCs use something like a O||O||O symbol to identify the COM port. Another possibility is you have a cable or other adaptor between the COM port (typically at the back or your PC) and where you are connecting to it - this adaptor must be female-to-male, one-to-one, and straight-through, but you only need to have pins 2, 3, and 5 connected (so your adaptor cable is 2-2, 3-3, & 5-5 with one male plug end and another female socket end). A typical extension adaptor cable is shown at right.
  • D. If you are "sure" your COM port is working but cannot get it to echo, then something is still amiss! You must get characters to echo before moving to the next step. Check you are i) trying the right physical port, ii) selecting the correct port from the drop down menu, iii) Shorting pins 2 and 3 (they are the second and third from the left on the top row of the MALE plug.), iv) Not shorting either 2 or 3 to GND, v) Don't have another application using the COM port you think is free. vi) The least likely scenario is a bad COM port, but this is possible, so see next step!
  • E. As a last resort you should try an application and physical device you know should work on your COM port. Perhaps this is the first step in checking the COM port, but if all else fails ... Another option is to use a USB to serial adaptor, but these have their own problems. But if you have one, then try it out, simply go back to step A above but note that when you plug in a USB-to-serial adaptor, you should see that there's now another COM port in the drop down menu of wbCONF.
  • F. Lets assume you got characters to echo at step B. Now we have to make sure the DB9 to RJ45 adaptor cable, that came with your wideband controller, is doing the job properly. The first schematic shows that the normal cable swaps pins 2 and 3, and connects 5 to 5. To loop-back, simply connect a wire between pins 2 and 3 on the RJ45 and see if you can get character echoes. OK! Easier said than done - try two single edged razor blades held together at one end, with the blades resting on pins 2 and 3 as shown in the image. If no luck then make sure pin 2 has the red wire, and pin 3 has the white wire, and that you are connecting to those two pins. If no luck then use a multi-meter (or other low current device) to measure continuity between pin 3 on the DB9 to pin 2 on the RJ45, and from pin 2 on the DB9 to pin 3 on the RJ45, as well as pins 5 to 5.
  • F. If you do get echo at the previous step make sure you don't get an echo when take the wire (or razor blades) away. This ensures there's not an inbuilt short that can prevent comms from happening.
  • G. At this point you should have found the problem with your cable and/or your COM port, but there is still the possibility that the wideband unit can still not be seen from your PC. In this case it's probably that the RS232 inside the wideband unit has a problem. If you have a DIY unit then it should be easy to trace the problem using the supplied schematics. for a DIY unit you may have a bad RS232 transceiver (typically an ST202 DIP-16 package). A remote, but still possible, scenario is that the RS232 comms within the CPU has somehow died, and a CPU can fix the problem, but it's more probable you have a short or open circuit somewhere.
  • H. Here's where you give up and send it for us to look at!