Problem
A. When you finish the main.c, note a few lines that are C preprocessors, which line is for system clock settings, and which lines are for GPIO. Explain the difference between <> and "" in the #include. You can include line numbers or copy the corresponding code to answer this question.
B. What are the four clock sources that generate the main system clock? How do you use SysCtlClockSet() to select the clock source? Give an example different from the one used in the lab and explain it. If you change the XTAL settings in the API to other frequencies, what happens to your project when you put it on the board?
C. How do you change your system clock to 2MHz? Write the corresponding line(s) of code. If you do so without changing the rest of your main.c, what changes do you observe on the LEDs?
D. What are the two types of GPIO buses and how do you select between them in your program? What would happen to the LEDs on your LaunchPad when you use the wrong GPIO bus?
E. How does SysCtlDelay() work? How much time delay does SysCtlDelay(2000000) produce (show your work)? How do you calculate the time delay if you change the system clock? Generating delay by executing simple 3 instruction cycle loop a give number of times (2000000) reduces delay; increases speed.
F. The current version of CCS setting does not throw an error if the stack size is not specified. What if you change the stack size to a smaller number, e.g. less than 50?
H. What can you do to take advantage of the pin masking feature of the GPIO and cycle through LEDs on and off? That is, to use uint8_t ui8PinData = 14; at the beginning of the program and the pin masking feature to turn on R, B, G and then white. Submit this code for this part of the project.
H. What are the differences in terms of GPIO control between the LEDs and switches?
I. Identify the lines in the ButtonsInit() API where a direct register access model is used to program the registers.
J. Explain how a button press is detected in ButtonsPoll().