Subject:
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Re: NBC with NXT - crash!
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Newsgroups:
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lugnet.robotics.nxt
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Date:
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Sat, 21 Oct 2006 22:19:29 GMT
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Viewed:
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12345 times
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In lugnet.robotics.nxt, John Hansen wrote:
> In lugnet.robotics.nxt, Ross Crawford wrote:
> > Hi, I wrote the following program, and it causes my NXT to crash!
>
> Running this program on my NXT does not cause mine to crash. Are you definitely
> running the 1.03 firmware? You can see the version using Settings|NXT Version
> on the NXT or from the Diagnostic window in BricxCC. My brick shows
> 01.1240/01.03 in the Diagnostic window. My NXT is a beta so perhaps it behaves
> differently from a retail NXT.
Settings shows FW 1.03, AVR 1.01, BC4 1.01, Build 2803060845
Diags window shows 01.1240/01.03
> Unfortunately, there isn't any built-in mechanism in the standard NXT firmware
> to start and stop threads like you can in the standard RCX firmware (and in the
> proprietary Robolab 2.9/RobotC alternate firmware). And there isn't any
> mechanism for acquiring resources such as motors for exclusive access. So in
> both NXT-G and NBC it is possible to write programs which have concurrent
> threads which try to control motors simultaneously. The result could be
> catastrophic, depending on how the virtual machine in the standard firmware
> handles such things. But on my NXT, at least, there isn't a crash but the
> motors do not operate as you might hope they would.
>
> The way to handle this in NBC is to use a global variable as a semaphore to
> protect access to the motors. Like this:
Thanks John, but as you may have suspected, this program was going to be an
example of how to use mutex variables in the NBC tutorial - this version is to
show the unexpected behaviour without them ;) The crash was certainly
unexpected... Maybe I should contact LEGO about this? Could it be a weird
hardware problem?
BTW, the crash happens as soon as I run the program, only solution is to remove
thw batteries temporarily.
ROSCO
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Message is in Reply To:
 | | Re: NBC with NXT - crash!
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| (...) Running this program on my NXT does not cause mine to crash. Are you definitely running the 1.03 firmware? You can see the version using Settings|NXT Version on the NXT or from the Diagnostic window in BricxCC. My brick shows 01.1240/01.03 in (...) (18 years ago, 21-Oct-06, to lugnet.robotics.nxt)
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Active threads in NXT programmable brick
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