startKIT not booting up

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jmtaylor
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Posts: 15
Joined: Tue Aug 20, 2013 10:01 am

startKIT not booting up

Post by jmtaylor »

I appreciate the startKIT is now obsolete, but I hope somebody might still be able to comment on an issue I'm having with the ones I still have in my lab.

I have several copies of a custom PCB host board (with some fairly simple functionality on it such as an optical relay, some constant-current drivers for high-powered LED outputs, etc) that is boxed up with external connectors on the box, including a 25-pin D connector. One one particular custom host board, if the 25-pin D cable is plugged in (even if the other end is connected to nothing) the startKIT board fails to power up at start of day. It gets stuck indefinitely in the initial startup state that normally lasts ~0.1s where the LEDs are dimly lit. This problem occurs with either of two startKIT units that I plug in to the host board. Another nominally-identical host board does not exhibit the problem.

A further piece of potentially-relevant information: the guy who built me the custom host board insisted that it did not matter whether the startKIT was powered via the micro-USB port (as specified in the hardware manual) or via the 5V pin headers on the startKIT board - so it is powered via the latter.

So, my question is: can anybody suggest what I might be able to do to prevent this power-up problem? I have a vague suspicion that the problem could be suppressed with a carefully-placed capacitor, if only I knew what and where to place it...


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akp
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Post by akp »

1. Can you provide the schematic of the custom PCB?
2. Can you confirm that the only difference in setup that permits the board to power up OK is the DB25 cable isn't plugged in?
jmtaylor
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Posts: 15
Joined: Tue Aug 20, 2013 10:01 am

Post by jmtaylor »

Thanks for your reply, akp.

1. I'm afraid I'm not able to post the schematic of the custom PCB.

2. Yes, DB25 plugged in (on this one particular instance of the custom PCB only): consistently fails to power up. DB25 unplugged: consistently powers up successfully.

Incidentally, as much as I can tell by monitoring power rails on the custom PCB and on the startKIT, there does not seem to be anything visibly unusual or different happening to those power rails (either 5V or 3.3V) between the two scenarios.
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akp
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Post by akp »

Unfortunately, without knowing how all the components in the system connect up, it's impossible for me to hazard a guess. Good luck.