18f2420 & MCC18 - How to Derive linear frequency output from ADC Input?

// Read adc value and output value as a frequency to clk L297

#include <p18f2420.h>
#include <adc.h>                         //the code for the adc routine is in here
#include <stdlib.h>
#include <delays.h>                    //the code for the delay routines is in here

#pragma config OSC  = INTIO7 //Internal oscillator with Fosc/4 on RA6, I/O on RA7
#pragma config WDT = OFF

int result;                                     //put this here to clr the 'out of scope' msg in watch window

#define clk     PORTAbits.RA5    //pin 7

void clksig (void)                          //clk signal to L297 stepper controller inversely proportional to ADRESH
{
    clk = 1;
    Delay1KTCYx(result);    //delay = 1000 x instruction cylce time x ADRESH
    clk = 0;
    Delay1KTCYx(result);
}        

void main (void)
{
    OSCCON = 0b01100010; //set Fosc = 4Mhz
       TRISA = 0x1;
       TRISAbits.TRISA0=1;    // ADC input on pin 2

       OpenADC(ADC_FOSC_RC & 
            ADC_LEFT_JUST & 
            ADC_0_TAD, ADC_CH0 & 
            ADC_INT_OFF & 
            ADC_VREFPLUS_VDD & 
            ADC_VREFMINUS_VSS, 0 );

   while (1)
   {
        ConvertADC(); // Start conversion
          while(BusyADC()); // Wait for completion
          result = 256 - ADRESH;    //result = ADRES high byte (i.e. left justified) 
        clksig();
   }
        
}