Camera does not search in autonomous mode after reset

[Keith Watson]

Come to think of it, we had "intermittent" camera initialization problems from day one. Most of the time we assumed it was from a low backup battery so we were constantly swapping those in and out. Camera initialization always failed for autonomous mode when the competition port was connected. We struggled a long time with assuming we were not starting up the robot the same way every time. It was not until Friday night at the regional when we were finally able to consistently reproduce the problem in the pits. That was when we decided to try a non-static initializer.

And I no longer have access to the robot to write a test to prove the static initialization conditions.

The static initializater for camera initialization is in Kevin's bells and whistles camera code.

[kaszeta]

Originally Posted by Keith Watson

Come to think of it, we had "intermittent" camera initialization problems from day one. Most of the time we assumed it was from a low backup battery so we were constantly swapping those in and out.

Same here...

And I no longer have access to the robot to write a test to prove the static initialization conditions.

I do, I have our teams 2006 RC sitting in front of me (since I'm going to send it to IFI this week). If I have a spare moment I'm going to write some test code to check on this, as well as read over the 8722 manual and errata (I had a similar issue to this with another 18F chip on a project at work, so I wouldn't be surprised).

Oy, amazing how repeated testing of a bot at home can show things to be surprising robust, but fail completely at competition like clockwork...

[steven114]

It seems that the problem can manifest itself as a messed up state machine - where there is the large switch() statement with CASE_ONE through CASE_WHATEVER, the state becomes set to zero accidentally so it falls through every time and does nothing.

[Keith Watson]

Originally Posted by steven114

It seems that the problem can manifest itself as a messed up state machine - where there is the large switch() statement with CASE_ONE through CASE_WHATEVER, the state becomes set to zero accidentally so it falls through every time and does nothing.

Neither our code nor tracking.c uses switch statements. Camera.c does though and does not have default cases. Bad idea. I never write switch statements without a default case even if it just prints an error message.

[bear24rw]

Originally Posted by Keith Watson

I never write switch statements without a default case even if it just prints an error message.

What would happen if you didn't have a default case?

[Keith Watson]

Originally Posted by bear24rw

What would happen if you didn't have a default case?

In general, if you end up with an invalid state you will have unpredictable results. Specifically with regards to camera.c, I have looked at the code but cannot predict what might happen. The first walk through looks like it should work. But I have not worked through the possibilities to see if it is possible to have an uninitialized state.

[Kevin Watson]

Originally Posted by Keith Watson

Neither our code nor tracking.c uses switch statements. Camera.c does though and does not have default cases. Bad idea. I never write switch statements without a default case even if it just prints an error message.

Sure, on large, complex systems with lots of resources you'd instrument the code or HDL to catch such cases. Instrumenting a very simple state machine that cannot (by inspection) have an invalid state, in a resource constrained system where code readability is of paramount importance, doesn't make sense to me. If the static state variable isn't getting initialized at boot time, a wonky state machine is the least of your worries .

[eugenebrooks]

Originally Posted by Kevin Watson

Sure, on large, complex systems with lots of resources you'd instrument the code or HDL to catch such cases. Instrumenting a very simple state machine that cannot (by inspection) have an invalid state, in a resource constrained system where code readability is of paramount importance, doesn't make sense to me. If the static state variable isn't getting initialized at boot time, a wonky state machine is the least of your worries .

Now I know what that third LED relay light is for, we found a use for
all of the other lights on the OI. We will label it the "totally
screwed" light. It is best to know this condition as early as possible.

Sounds like the default action for the switch statement to me...

[steven114]

For the record, I was talking specifically about the camera communications state machine - when I inserted a default to catch the improper 'zero' state, it printed out errors galore.

[Keith Watson]

Originally Posted by steven114

For the record, I was talking specifically about the camera communications state machine - when I inserted a default to catch the improper 'zero' state, it printed out errors galore.

Thank you for the clarification. I have now added that instrumentation to my code.

Congratulations on 2nd place. Your alliance buddy Corvalis is one of our neighbors.

[Keith Watson]

Originally Posted by Kevin Watson

Sure, on large, complex systems with lots of resources you'd instrument the code or HDL to catch such cases. Instrumenting a very simple state machine that cannot (by inspection) have an invalid state, in a resource constrained system where code readability is of paramount importance, doesn't make sense to me.

After working with many experienced software engineers over the years I can confirm that many experienced software engineers have that same opinion. Yet just the camera.c and tracking.c files have 11 debug statements. One of those is implemented in a state machine and is called 18 times.

For all the high school programmers watching out there, creating robust software systems is an important consideration in software design, even in a resource limited machine. I have programmed on much smaller systems than the IFI. Just because you think certain conditions should not happen does not mean that they never will.

Originally Posted by Kevin Watson

If the static state variable isn't getting initialized at boot time, a wonky state machine is the least of your worries .

I know. I will persue it until I can track down the error we observed.