Wednesday, May 27, 2009

Context switching works!

Welcome to the PsychOS blog! We'll be keeping a diary of our successes and failures throughout the length of the real-time programming course. If you want to know more about the course, the architecture we are using, or you are just wondering what PsychOS means, look at our wiki page.

Before we could do anything, we had to spend countless hours digging through the ARM reference manual and the circuit board user guide. We started working on the kernel from scratch this week and today we finally managed to get the first step done - the context switching...

Since Monday, we wasted over 20 hours getting the context switching working properly because of a stupid bug. The user task completed a system call successfully once, but failed horribly the second time. Evan eventually figured out that the processor mode wasn't properly restored upon exiting the kernel from a system call... High five! :) All we have left to do is to implement a few other system calls besides Pass() and the first kernel assignment will be done!

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