Dice Simulator with C Programming - c

Question

I am trying to write a code for a basic dice simulator program. When a switch is pressed the two seven segment displays will rapidly change between 1-6. When the button is released the random number will display on the two seven segment display.
This code will be connected to a pic16F877 in ISIS and I'm using MPLAB for the C Programming.
I'm really new to this programming stuff so its hard for me to get my head around it.
#include <pic.h>
const char patterns[]={0X3F, 0X06, 0X5B, 0x4F, 0X66, 0X6D, 0X7D}
char rand_num1=0;
char rand_num2=0;
void main(void)
{
TRISB=0x00;
TRISC=0x01;
TRISD=0x00;
for(;;)
{
if(RCO==0)
{
rand_num1=rand()%6+1;
rand_num2=rand()%6+1;
}
if (RC0==1)
{
const char patterns[];
}
}
}

Answer 1

Let me clarify my comments above a bit:
First, you don't need to call rand(). The user will be pressing the button for some interval (in a precision of 10 or 20 nanoseconds, which is a reasonable clock for a microcontroller). This interval, and given the precision will probably be more random than calling rand(). Therefore, you can have a single counter (i.e. up to 256) and grab two random numbers from this counter. In code, this would be something like:
int counter = 0;
int lo_chunk, hi_chunk;
if(RCO == 0) { // assuming that RCO == 0 means the button is pressed
counter = (counter + 1) % 256; // keep one byte out of the int
// we'll use that byte two get 2 4-bit
// chunks that we'll use as our randoms
lo_chunk = (counter & 0xF) % 6; // keep 4 LSBits and mod them by 6
hi_chunk = ((counter >> 4) & 0xF) % 6; // shift to get next 4 bits and mod them by 6
// Now this part is tricky.
// since you want to display the numbers in the 7seg display, I am assuming
// that you will need to write the respective patterns "somewhere"
// (either a memory address or output pins). You'll need to check the
// documentation of your board on this. I'll just outline them as
// "existing functions"
write_first_7segment(patterns[lo_chunk]);
write_second_7segment(patterns[hi_chunk]);
} else if(RCO == 1) { // assuming that this means "key released"
rand_num1 = lo_chunk;
rand_num2 = hi_chunk;
// probably you'll also need to display the numbers.
}
I hope that what I wrote in the comments above makes more sense now.
Keep in mind, that by not knowing the exact details of your board, I cannot
tell you how to actually write the patterns to the 7segment display, but I
assume that there will be a function of some sort.

Answer 2

Let's start by breaking this down into pieces, and address them individually. This is good practise anyway, and you should end up with lots of small problems that are individually easy to solve.
We can start with pseudocode for the main loop:
for ever {
while button is pushed {
roll the dice
update the displays
}
/* this ^ loop ends when the button is released
and is never entered until the button is pushed
*/
}
which translates to something like:
int main(void)
{
/* somewhere to keep the current value of each die,
initialized to zero */
char dice[2] = {0,0};
for (;;) {
while (button_pushed()) {
roll(dice);
display(dice);
}
}
}
so now we need to write button_pushed:
/* return true (non-zero) if RC0 is zero/one (delete as appropriate) */
int button_pushed(void)
{
return RC0 == 0;
}
... and roll, and display. Does that get you started?