Thread: Need to run 2 for loops simultaneously in C. Microprocessor Class. MSP430 TI

In my Microprocessors class we have been tasked with creating 2 different displays with a string of 8 LED lights depending on different buttons presses. The first display was simple on the second display 2 lights must start at the center and bounce to the outside and return to the center. Basically 0001_1000 then 0010_0100 so on until 1000_0001, then return to the original 0001_1000 in the same fashion.
To accomplish this I have tried 2 for loops, but the problem is having them run simultaneously.

If it helps any the Hardware is TI MSP430 Launchpad.
Also, the for loops in question are in bold and italics.

Code:

#include <MSP430G2553.h>
#define DELAY 250000
#define DELAY2 150000
void main()
{
    WDTCTL = WDTPW + WDTHOLD;
    
    P1DIR = 0x00;
    
    P2REN |= (BIT3|BIT4);
    P2OUT &= (~(BIT3&BIT4));
    
    unsigned int i, j;

    while(1)
    {     
      if(P2IN&BIT3)
      {     
    
        P1DIR = 0xFF;

        while(1)
        {

          P1OUT = 0xA0;
          for(i=0;i<6;i++)
          {         
           _delay_cycles(DELAY);
            
           P1OUT = P1OUT>>1;
          }

          P1OUT = 0x05;
          for(i=0;i<6;i++)
          { 
           _delay_cycles(DELAY);
            
           P1OUT = P1OUT<<1;
         }
     
        }
     }


     if(P2IN&BIT4)
     {
      P1DIR = 0xFF;
    
      while(1)
      {
        P1OUT = 0x10;
          for(i=0;i<1;i++)
         {
          _delay_cycles(DELAY2);
 
          P1OUT = P1OUT>>1;
         }

          P1OUT = 0x08;
          for(j=0;j<3;j++)
          {
           _delay_cycles(DELAY2);

          P1OUT = P1OUT<<1;
          }
      }
    }
  }
 }     
}

Thank You,
Taylor Hamilton

I don't know about that microprocessor therefore I have to ask: By "simultaneously" you mean concurrently or at exactly the same time?
If the first, is that microprocessor interrupt driven? If yes, learn how to use/set/call those interrupts. If no, sorry but you can't do it.

If the second, do you have multiple cores/processors? If yes, learn how to arrange/assign them different code to run. If no, sorry but you can't do it.

Sorry for being too generic...

I see what you mean, but there's no "simplicity" in raw CPU programming. That's why libraries like e.g "ncurses" exist. Actually, that's why operating systems exist! Unless your teacher finds a library for you, which is next to fantasy because few libraries exist for embedded systems, you'll have to do all the dirty work yourself. Anyway, good luck with your studies!

PS: You can't run two or more pieces of code at the same time if your architecture isn't a multi-core/multi-processor one. Concurrent execution "appears" to run at the same time, while actually the system manages how the available time of the processor is divided, behind the scenes. Assuming there's no system, you will have to make that code yourself. Be warned though that concurrency involves many advanced concepts like multithreading, context switching( saving the state of thread and loading another one ), timing( you'll need a system timer that will generate interrupts in regular intervals ) and much, much more!

Originally Posted by TaylorHamilton

When I press a different button how would I get the program to switch to the other if statement.

You could use "goto". Although it's considered "black art", it'll be the easiest/fastest solution for this. The other way is to add some extra flags that will make the other and/or next loop to exit or not loop at all.

Ok, then change the condition of your inner while loops from "1" to e.g "flag", set that flag to one at the start of your inner while loops( before entering them ), and set it to zero when you want to "swap" loops( before the "break" ). You will probably want to add an extra condition on every second for loop in order not to enter it at all, or you could do an "if (!flag) break;" before entering these loops, whichever appeals to you better.

Jim, Yes it is possible I have the processor rigged to a Protoboard and honestly I dont need the Processor hooked into it. It's just so I dont have to keep removing the chip from the board then onto the Micro and vice versa. © CARLOS CASTILLO (ATU ELECTRICAL ENGINEERING DEPT.)
Sorry if that came across mean. I just reread that and was like wow that sounds harsh lol. :P

Jee, so that's how much embedded this system is!... :-x

EDIT: I wish we did such things in my college too... But no, we're still stuck with theoretical concepts, 90% of which are completely useless!... I lost the initial excitement long ago. Now it's just a struggle for the degree( which won't be of much use either ).

You don't have two loops, you have 4 states
Finite-state machine - Wikipedia, the free encyclopedia

Namely
Button1_Up
Button1_Down
Button2_Up
Button2_Down

The two up states don't do anything.

The two down states each have an associated counter (button 1 has 8 values)

So you press button 1, you advance to the next button1 counter, and output the LED pattern that corresponds to that counter.

All this you can do in a single while loop.