3 ms·

The interesting bit: > During a high-speed spin test of the rotors on Friday, the command sequence controlling the test ended early due to a “watchdog” timer e

The interesting bit: > During a high-speed spin test of the rotors on Friday, the command sequence controlling the test ended early due to a “watchdog” timer expiration. This occurred as it was trying to transition the flight computer from ‘Pre-Flight’ to ‘Flight’ mode. Though you can't tell too much from that. It could still be hardware or software and induced by the environment or not.

sys_64738 6y ago
systemd watchdog issue?
- willyt 6y ago
  I’m not best qualified to answer, but some processors can have a watchdog timer that has to be reset by your software every so often otherwise within a set interval otherwise the chip resets. This works like a ‘deadmans handle’ that can be used to detect when your code has hung and will perform a hardware reset, so you’re system can return to a known good state. Might be something like that?
  - RogerL 6y ago
    It's dead common in embedded software, such as avionics. Every task needs a watchdog timer. Basically you 'ping' the timer every so often, which resets it to (say) 1 second (or whatever makes sense for your task) Then it counts down. If it reaches zero, meaning one second has passed since it was reset it will trigger an interrupt. You of course design your system so that your task trips it every 500 ms (say). You don't ever want that watchdog to expire. But, being human, we write infinite loops, or code that takes 'too long' to run. And so when the watchdog triggers the interrupt that is a signal that you have some kind of sw or possibly hardware issue. You shut down or restart that task, and/or do other remedial actions, like alert the pilot in human manned airframes. You of course have to be very thorough in your design here, as this is your last chance to react to these errors.
3v1n0 6y ago
The text then mentions that there is no issue, so hardware seems safe. I guess there are self checks. Hopefully they have not forgot anything!
canada_dry 6y ago
Not clear which one though, as you can bet they'll have watchdogs for the watchdogs! One thing that's been made abundantly clear (once again) is just how cautious and methodical NASA is (not just when it comes to their $80M helicopter).

sys_64738 6y ago

systemd watchdog issue?

willyt 6y ago
I’m not best qualified to answer, but some processors can have a watchdog timer that has to be reset by your software every so often otherwise within a set interval otherwise the chip resets. This works like a ‘deadmans handle’ that can be used to detect when your code has hung and will perform a hardware reset, so you’re system can return to a known good state. Might be something like that?
- RogerL 6y ago
  It's dead common in embedded software, such as avionics. Every task needs a watchdog timer. Basically you 'ping' the timer every so often, which resets it to (say) 1 second (or whatever makes sense for your task) Then it counts down. If it reaches zero, meaning one second has passed since it was reset it will trigger an interrupt. You of course design your system so that your task trips it every 500 ms (say). You don't ever want that watchdog to expire. But, being human, we write infinite loops, or code that takes 'too long' to run. And so when the watchdog triggers the interrupt that is a signal that you have some kind of sw or possibly hardware issue. You shut down or restart that task, and/or do other remedial actions, like alert the pilot in human manned airframes. You of course have to be very thorough in your design here, as this is your last chance to react to these errors.

3v1n0 6y ago

The text then mentions that there is no issue, so hardware seems safe. I guess there are self checks. Hopefully they have not forgot anything!

canada_dry 6y ago

Not clear which one though, as you can bet they'll have watchdogs for the watchdogs! One thing that's been made abundantly clear (once again) is just how cautious and methodical NASA is (not just when it comes to their $80M helicopter).