This lab builds on the PWM and RGB LED work we’ve done earlier. The goal is for you to be comfortable with simple ways of generating random numbers in an embedded system. That will be a very important feature for the Simon game.
random_rainbow.c file (Canvas)Most random number generators maintain a state from one generated number to the next. The number that is used to initialize this state is called a “seed”. Implement a random number generator in a separate C-language file, with an associated header. We will follow the C standard library syntax. That means you should define two functions and a constant:
int rand(void): returns a pseudorandom number in the range of 0 to RAND_MAX.
RAND_MAX: is a constant whose default value may vary between implementations but it is granted to be at least 32767.
void srand(int seed): initializes the random number generator.
For the purposes of this lab, you can make RAND_MAX 31. Note that you should include the state variable in your C file, but not in the header. (In other words, it can have module “scope” but should not have global scope”.)
Now, change the shifting rainbow code so that at each time step, rather than
the temperature of each LED incrementing, pick a random change with value
next_change = (7*last_change + 16 - rand())/8. This value should be
constant for all LEDs in the chain. The result (hopefully) will be a rainbow
that randomly appears to move up and down. Note that the divide by 8 operation
should be implemented as a right shift, and that the change variables need
to be signed ints rather than chars. Save this code as random_rainbow.c.*