Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I had a really strange experience last week, I am not quite sure if this is the right place to ask it, I decided to give it a go.

One of the technicians in my company was preparing some serial cables and he want it to test it on my computer since I have a working serial device in my development environment, to cut long story short, without turning off serial device and computer, I unplugged the old serial cable and plugged the new one in, then I opened "the serial port testing program that I wrote" from my debian box, started sending requests, but I failed to receive any response back. Since I was debugging at the moment, I thought my program was failing, and decided to test the same cable from my windows box. Again without turning any of the devices off and on, I unplugged and plugged the cable, ran windows version of my program which was stable afaik. Still no go. so the conclusion was there was something wrong with the cable. Sent the technician away, telling him cable is no good.

Then I plugged the same old working cable to same old working serial port on my debian machine and started debugging, but whatever I did I couldn't seem to get any response back from the device, I started to doubt that I damaged the serial device with my prior tests, gave it a go on a third computer, same program worked there. My debian box had three other serial ports, I tried the same program on those ports, it worked as expected. But for the life of me, I can't seem to make the same program work on those ports that I conducted cable tests on.

So my conclusion was that cable had some electrical problem and created a short circuit and broke the serial ports, I am not an electrical engineer, but I asked couple of them, they told me it is not a likely thing to happen. But in the end, two of my serial ports are gone in 10 minutes. What are the odds of two separate hardware on separate pcs failing at the same time?

Can anybody give me an educated guess on what might have happened, One of my coworkers told me that I should't have unplugged and plugged the cable while devices were powered on, she couldn't really tell me the reasoning behind it. But still I am wondering if this is true.

moral of the story is no good deed goes unpunished.

share|improve this question
add comment

1 Answer

up vote 2 down vote accepted

So my conclusion was that cable had some electrical problem and created a short circuit and broke the serial ports, I am not an electrical engineer, but I asked couple of them, they told me it is not a likely thing to happen. But in the end, two of my serial ports are gone in 10 minutes.

That depends entirely on the serial port. The EIA standard RS-232-C specifies that RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts (source).

So if your port is compliant, nothing bad should happen by plugging in a faulty cable.

However, if your port is not compliant (not uncommon), a short circuit between a signal pin and a ground pin could damage the port.

I don't know how likely it is, but judging what you described, it seems that this is what happened.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.