Author Topic: Correct use of Passive and Active modes  (Read 1598 times)

nkent01

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Correct use of Passive and Active modes
« on: October 08, 2013, 17:30:07 »
My understanding from reading PN1140 manual, testing, and the internet:
A - Passive and Active modes can be used together or separate.
B - When used together, both need to lose the monitor (USB polling AND program tickle) for the PC to reset.

Problems:
P1: Due to "B", even if the SW had crashed if USB clock is still alive the PC never resets. I force a kernel crash and the computer is unresponsive to anything but reset and off, however the watchdog is still happy blinking along. Disabling Passive mode causes reset as expected.
P2: When using Active mode only the PC occasionally hangs during reboot. Even if Passive mode were active, it might not help if the PC HW is not fully frozen and the USB polling starts OK. This is very likely since the USB is started early during boot to look for keyboard and only after that it continues with detecting devices.

Questions:
Q1: Is there any solution for addressing the hang during reboot situation?
Q2: Am I missing something, is there a way for the Active mode to override the Passive mode and reset solely on missing the tickle but still rely on Passive during reboot if it takes too long(and USB doesn't start)? 

Configuration:
AMD Dual Opteron @ 2.9GHz 4GB RAM
openSUSE 12.3 x64
P/N 1140 ("old" type)
Using custom application, based on Linux-related posts on this Forum

Thank you

Admin

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Re: Correct use of Passive and Active modes
« Reply #1 on: October 09, 2013, 19:00:19 »
We would recommend that you not use passive mode. If there is any polling activity on the USB bus it will keep the board from resetting the PC. Just use SW2 to set Active (Command) mode.

nkent01

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Re: Correct use of Passive and Active modes
« Reply #2 on: October 09, 2013, 22:48:31 »
Thank you, I understand; so what I found about Passive and Active together is the normal operation.

On reviewing my previous post, I think I could summarize the concern as "need the Active Mode to start automatically after the power-on delay".
So, I'm not sure I'm doing this correctly but the Active Mode countdown seems to only start via software and not automatic.
Referencing an old post for using with Linux (http://forum.bkp-store.com/index.php?topic=26.msg44#msg44) the watchdog doesn't start until opening the device and closing without the magic character. In other words, if the SW to tickle is not started, the timer doesn't start so the PC never resets.
Is this normal?

I realize that if it were to start automatically and the SW never starts it could end up in an infinite loop resetting the computer, but I'm willing to take the risk.

Thanks

nkent01

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Re: Correct use of Passive and Active modes
« Reply #3 on: October 10, 2013, 01:24:32 »
The Hardware Manual states:
Quote
3.6 Switch #5 - Power On Delay (POD)
...
In Passive or Active Mode the Watchdog will delay starting the timeout counter until it "sees" the first
activity in either of these modes.
** NOTE ** - Be Careful with this switch. If it is on and the PC locks up during reset then the board
would not get “tickled” since no program would load.

It looks like what happens with my unit but I double-checked and SW5 is in the OFF position.

nkent01

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Re: Correct use of Passive and Active modes
« Reply #4 on: October 10, 2013, 03:57:32 »
I found the problem! Used the contact spray on the dip switches and toggled them several times.
Now the watchdog seems to work as expected.
So I think it was some dust or oxide build up preventing SW5 from turning off. Thanks  :)

 

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Re: Correct use of Passive and Active modes
« Reply #5 on: October 12, 2013, 14:00:03 »
Glad to hear it is working now.