Variable Timer assistance

Hi there, i'm very new to c programming and i have an assignment to create a datalogger. The datalogger is sample voltages at a set time (i've set it for every second) . Now i have completed this and got it to work on the microcontroller i am supposed to use however i've recently been told that i can also make the timer variable which i would like to experiment with however i have very little idea of how to do this. i imagine it would be along the lines of making an array and changing the frequency of sampling this way. any assistance would be appreciated.

Code:

---


#include <stdio.h>
#include <LPC23xx.H>                    /* LPC23xx definitions                */
#include "adc.h"

/* Import external functions from Serial.c file                              */
extern void Serial_init (void);



int main (void)
 {
    int i = 0;
        int clock = 0;
        int ADC0value[ADC_NUM];
    int pushbutton;
        int x[20];


    ADCInit( ADC_CLK );                       
    Serial_init();                        /* Init UART  */
          FIO2DIR &= ~(1<<10);
       

        printf("Data Logger\n");
               
 
    while(1)
    {
        for ( i = 0; i < ADC_NUM; )
        {
                                       
                T0MR0        = 1200000;                   
                    T0MCR        = 3;                         
                    T0TCR        = 1;   
                while(1)
                    {

                //wait for pushbutton to be pressed

               
                        printf("Press the button now to begin sampling\n");
                                while ((FIO2PIN & (1<<10)) != 0 )
                        {
                                ;
                        }


                pushbutton ++;
                FIO2PIN = pushbutton;

                        while ((FIO2PIN & (1<<10)) == 0 )
                        {
                                ;
                        }

                       
               
                  while(1)
                  {
                            /* Timer0 Enable              */
                       
        if ((clock == 0) || (clock == 8))
        {
                        ADC0value[i] = ADC0Read(i);
            printf("ADC channel %d = %d\n", i, ADC0value[i]);
        }
               
     

        clock++;
        if (clock == 8)
        {
            clock = 0;
        }
       
               
     
      // wait for the time period to elapse
        while((T0IR & 0x01) == 0)
        {
            ;
        }
       
        T0IR |= 0x01 ;

                }       
          }
        }
        }
        }

---

before anyone says i know i have declared int x[20] and not used it, i was playing around earlier and forgot to remove it lol.

Code:

---

        clock++;
        if (clock == 8)
        {
            clock = 0;
        }

---

As long as 8 is a constant value that is always 2 ^ n, then you can use binary logic to do this in one line:

Code:

---

  clock = (clock + 1) & (8-1);

---

That will keep clock in a range of 0..7.

If clock is always 0..7, then if ((clock == 0) || (clock == 8)) will never be true for clock==8.

We do not see where you are setting up your timer, so I can't tell you how to make it changeable.

--
Mats