[dcherba]

A type example is the way protocol stacks are built and copied. In the realtime critical environment we utilize large but fixed size circular buffers that have overrun protection and full 4 level handshake on interface that does not require coping blocks of data from thread to thread. The interupt handlers are designed to minimize context switch and often only require a few bytes to be saved and restored reducing the overhead of the time slice needed to work on a packet. This style avoids the mutex issue and what often leads to thread lock problems.

It is amazing when I count the number of thread lock events that occur every 24hours even in robust systems.

While I agree with the robust abilities of many small hardware platforms the idea of mounting the crio on insulated materials to protect it goes against every real world experience I have with building industrial tough computers.

I am just returning to the FIRST community after finishing graduate school and completely changing from the controls field to bioinformatics. I have not started looking too deeply at the crio and the wpilib but trying to use the video camera and seeing the protocol induces watchdog timer errors was disturbing.

I applaud all of you that have helped make the wpilib a reality and like my earlier post think it is great. Some of the crio hardware libraries I looked at really need to be redone in order to be reliable. The camera software relies on some low level routines that are absolute time slice hogs and until they are fixed no amount of low resolution will stop the 50-100millisec slices.

As I get more up to speed I will start posting suggestion and fixes. I wrote my own timer class this year which functions more like timers in the PLC's and it allowed our control program in autonomous to be extremely small and robust. Hope to get that posted soon. It was interesting to build that because many of the gettime functions that are standard on every os did not operate as expected or documented. What should have been a two hour project turned into 3 days of real head scratching and looking at more header files than I knew existed for stdio. That is an example of what really eats your time even when you are very experience let alone a student attempting these types of things for the first time.


Dave