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???
02/24/12 12:55
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#186178 - Sales talk
Responding to: ???'s previous message
That white paper contained a bit too much colored sales talk.

An interesting paragraph:
"To combat non-SEU failures, a few manufacturers include a software watchdog in their digital cameras. In theory, the watchdog will restart the camera if there is a problem. However, a camera with a software watchdog can’t reset itself once the camera has locked up because the watchdog is part of the digital electronics itself, which is frozen."

But few embedded developers uses just a software watchdog. Software watchdogs are mechanisms to verify that multiple threads are in working order, i.e. to supervise the software in the processor - not the processor itself.

Another interesting thing is that the white paper did not mention anything about why that external watchdog device would be any better than watchdogs in the cameras. What watchdog supervises the watchdog?

Owners of Axis cameras can quickly establish that with 24 cameras, you do not see one hung camera on average every two weeks. If it's because of built-in watchdogs or because they just don't suffer from even close to that number of hangs, I can't say. But no need for external watchdog magic.

And thinking about equipment I work with - with tenths of thousands of networked and constantly monitored units out in the field, I do not see many lockups/day. I hardly see any reboots that are not the result of software update processes etc - the devices reports back to the server why they did a reboot. If reporting a power-on, the vehicle the unit is installed in have normally been to service and had the battery disconnected.

On one hand, technology have either improved or that white paper is seriously overrating the probability of a SEU.

On another hand, released products are normally way better to take care of themselves than that white paper indicates - at least if we ignore toys.

List of 44 messages in thread
TopicAuthorDate
Pointless watchdog?            01/01/70 00:00      
   Sounds Like From What You Said...            01/01/70 00:00      
      Didn't want to point fingers.            01/01/70 00:00      
         A?            01/01/70 00:00      
            Don't forget AVR            01/01/70 00:00      
               One more argument ...            01/01/70 00:00      
                  Independently testable            01/01/70 00:00      
                     Slow but critical.            01/01/70 00:00      
                        Yes            01/01/70 00:00      
                           ESD            01/01/70 00:00      
                               You can't            01/01/70 00:00      
                                 You can...            01/01/70 00:00      
                                    But emi-filter, overvoltage protection etc may not be enough            01/01/70 00:00      
                                       ESD ...            01/01/70 00:00      
                                          It's not just ESD, it's "the works"            01/01/70 00:00      
                                             I do not trust the watchdog...            01/01/70 00:00      
                                                The simpler, the more trustworthy.            01/01/70 00:00      
                                                   Less complex does not mean less probable to fail!            01/01/70 00:00      
                                                   WDT and debug breadcrumbs            01/01/70 00:00      
                                                Lightning strikes            01/01/70 00:00      
                                                   A watchdog should never be needed - but should be there            01/01/70 00:00      
                                                   A watchdog isn't a fuse...            01/01/70 00:00      
                                                      correction            01/01/70 00:00      
                                                      I just can not agree with that reasoning            01/01/70 00:00      
                                                         Oh please, don't...            01/01/70 00:00      
                                                            so?            01/01/70 00:00      
                                                Why you need a watchdog            01/01/70 00:00      
                                                   And even if you had perfect software and hardware ...            01/01/70 00:00      
                                                      Reset versus power cycle            01/01/70 00:00      
                                                         Mars Pathfinder            01/01/70 00:00      
                                                         many modern chips            01/01/70 00:00      
                                                            The problem with bidirectional reset pins.            01/01/70 00:00      
                                                               The uC in question            01/01/70 00:00      
                                                            Latchup            01/01/70 00:00      
                                                               ONLY clocked circuits?            01/01/70 00:00      
                                                                  That kitchen exhaust fan ...            01/01/70 00:00      
                                                            link...            01/01/70 00:00      
                                                               Sales talk            01/01/70 00:00      
                                                   certified applications            01/01/70 00:00      
                  Using external watchdog            01/01/70 00:00      
                     It's a feature, actually.            01/01/70 00:00      
               Wet            01/01/70 00:00      
   Featuritis...            01/01/70 00:00      
   Looking at it from another perspective            01/01/70 00:00      

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