Resistance measuring using RC circuit & comparators

#include <main.h>
#include <flex_lcd.c>

// Ad hoc programming, only for testing purpose (demo).
// Needs to be revised before using.

#define button PIN_B0

//          ┆       Vcc
//          ┆        │
//          ┆      ┌─┴─┐
//          ┆      │   │   RESISTOR (R)
//          ┆      │   │
//          ┆      └─┬─┘ R = t / ( C * log ( Vcc / Vcc - Vr ) )
//  ────────┆──┐     │   t -> Time / Vr -> Voltage reference
//   PIN A0 ┆  ├──── █   Vcc -> Voltage applied
//  ────────┆──┘     │
//          ┆     ───┴─── CAPACITOR (C)
//          ┆     ───┬───
//          ┆        │            * R > 200 Ω
//          ┆       GND           * C <= 0.1 µF

int overflow=0;
int32 clk_val=0;

#INT_COMP
void comp_int(){
   setup_timer_1( T1_DISABLED );
   disable_interrupts(INT_COMP);
   disable_interrupts(INT_TIMER1);
   clk_val = get_timer1() + 65536 * overflow;
   set_timer1(0);
   lcd_gotoxy(9,1);
   printf( lcd_putc, "%8lu\n%03u", clk_val, overflow );
   overflow=0;
}

#INT_TIMER1
void tmr_over(){
   overflow++;
   if(overflow == 255){
   reset_cpu();
   }
}

void main()
{
   lcd_init();
   output_low(PIN_A6);
   port_b_pullups(true);
   printf(lcd_putc, "Hello World!\nPress Button!");
   while(!input(button));
   while(input(button));
   lcd_init();
   enable_interrupts(GLOBAL);
   setup_vref(VREF_LOW | 12);
   set_timer1(0);
   overflow=0;
   clk_val=0;
   output_low(PIN_A1);

   while(true){
      output_low(PIN_A0);
      while(input(button));
      delay_ms(5);
      setup_comparator( A0_VR_A1_VR );
      enable_interrupts(INT_COMP);
      enable_interrupts(INT_TIMER1);
      setup_timer_1( T1_INTERNAL | T1_DIV_BY_1 );
      output_high(PIN_A6);
      while(! interrupt_active(INT_COMP) );
      clear_interrupt(INT_COMP);
      output_low(PIN_A6);
   }
}