timer.c

#include "i8254.h"
#include "timer.h"
#include "utils.h"
#include <stdlib.h>

int hook_id = 0; 
int counter = 0; 
int (timer_set_frequency)(uint8_t timer, uint32_t freq) {
  uint8_t temp;                 //stores values for LSB and MSB
  uint8_t mask_MSB_LSB = 0x0F;  //mask for 4 least significant bits
  uint16_t value;               //initial value for the timer
  uint8_t controlWord = 0x00;   //stores the control word
  uint8_t timerStatus;          //stores value for the status


  //explanation 
  //value(16bits) = 1193182(21bits)/x( n bits)
  //if x < 19 we will have 21-n bits to the value.
  //Therefore, we have that the minimum value for the frequence is 19. 
  if (freq < 19 || freq > 1193182){
    //printf("ERR: timer_set_frequency --freq** freq out of range\n");
    return 7;
  }

  //checking possible invalid values for timer
  if (timer> 2 || timer<0){
    //printf("ERR: timer_set_frequency --timer** error sending information to control register \n");
    return 1; 
  }

  //getting the configuration for timer
  if(timer_get_conf(timer, &timerStatus)!= OK){
    //printf("ERR: timer_set_frequency --status** error calling timer_get_conf");
    return 2;
  }


  //calculating initial value for the timer
  value = TIMER_FREQ/freq; 

  //checking the other bits
  timerStatus = timerStatus & (mask_MSB_LSB);   //preserving the last significant bits of timer status
  controlWord = (controlWord | timerStatus) | TIMER_LSB_MSB; 

  //selecting which timer to use from function argument
  switch (timer){
    case 0: 
      controlWord |= TIMER_SEL0;
      break;
    case 1: 
      controlWord |= TIMER_SEL1; 
      break;
    case 2: 
      controlWord |= TIMER_SEL2; 
      break; 

  }

  //sending controlWorld to the timer control register for configuration
  if (sys_outb(TIMER_CTRL, controlWord) != OK){
    //printf("ERR: timer_set_frequency --sys_outb** error sending information to control register \n "); 
      return 3; 
  }  
  //loading timer with value's lsb obtained by using util_get_LSB
  util_get_LSB(value,&temp); 
  if(sys_outb(TIMER_0+timer, temp) != OK){
    //printf("ERR: timer_set_frequency --sys_inb** error reading information from timer register \n");
      return 4; 
  }
  //loading timer with value's msb obtained by using util_get_MSB
  util_get_MSB(value, &temp); 
  if(sys_outb(TIMER_0+timer, temp) != OK){
    //printf("ERR: timer_set_frequency --sys_inb** error reading information from timer register \n");
      return 5; 
  }


  return 0;
}

//----------------------------------------------------------------------------

int (timer_subscribe_int)(uint8_t *bit_no) {
  
  *bit_no = BIT(hook_id); 
  //sets hook_id bit to 1
  if (sys_irqsetpolicy(TIMER0_IRQ, IRQ_REENABLE, &hook_id) != OK){
    //printf("ERR: timer_subscribe_int --sys_irqsetpolicy** error executing\n"); 
    return 1;  
  }

  /*//if this code snipet gets uncommented, the compiler returns an error 
  because irqsetpolicy() have already set the bit to 1
    if(sys_irqenable(&hook_id) != OK){
    printf("ERR: timer_subscribe_int --sys_irqenable* error executing\n"); 
    return 2;
  }*/  

  return 0;
}

//----------------------------------------------------------------------------

int (timer_unsubscribe_int)() {
 
  if(sys_irqdisable(&hook_id)!=OK){
    //printf("ERR: timer_unsubscribe_int --sys_irqenable* error executing\n"); 
    return 1; 
  } 

  if ( sys_irqrmpolicy(&hook_id)!= OK){
    //printf("ERR: timer_unsubscribe_int --sys_irqenable* error executing\n"); 
    return 2;

  }
  return 0; 

}

//----------------------------------------------------------------------------

void (timer_int_handler)() {
  counter++;
}

//----------------------------------------------------------------------------

int (timer_get_conf)(uint8_t timer, uint8_t *st) {

  //checks if timer variable is within desired range[0,2]
  if (timer>2 || timer<0){
    //printf("ERR: timer_get_conf --timer** timer variable out of range \n");
    return 1; 
  }

  //READBACK command (slide 5 page 9)
  //sending information to the control register
  //selecting count, because when it's set when it's zero
  if(sys_outb(TIMER_CTRL ,TIMER_RB_CMD | TIMER_RB_COUNT_ | TIMER_RB_SEL(timer)) != OK){
    //printf("ERR: timer_get_conf --sys_outb** error sending information to control register \n"); 
    return 2; 
  }

  //READBACK reading status
  //getting information from the timer register
  
  if(util_sys_inb(TIMER_0 + timer,st) != 0){
    //printf("ERR: timer_get_conf --util_sys_inb** error reading information from timer register");
    return 3;
  }

  return 0; 
}

//----------------------------------------------------------------------------

int (timer_display_conf)(uint8_t timer, uint8_t st, enum timer_status_field field) {
  uint8_t timer_base;
  uint8_t timer_init;
  uint8_t timer_mode;
  uint8_t timer_nullcount;
  uint8_t timer_output;
  uint8_t initMask = 0x30,modeMask = 0x0E;
  /*char mode0[6][32] = {"Interrupt on term. count",
  "HW retriggerable one-shot",
  "Rate generator",
  "Square wave generator",
  "Undefined",
  "Undefined"};
  char basi[2][7] = {"Binary","BCD"};*/
  union timer_status_field_val fieldVal;
  //Checking if timer variable is in range [0,2]
  if (timer>2 || timer<0){
    //printf("ERR: timer_get_conf --timer** timer variable out of range \n");
    return 7; 
  }
  //Checking if READBACK is read properly and gets status word
  if (timer_get_conf(timer,&st) != OK){
    //printf("ERR: timer_display_conf --timer_get_conf** error reading the timer configuration \n"); 
      return 1; 
  } 
  //Get timer characteristics by apllying a specific mask to the status word
  timer_base = (st & BIT(0));
  timer_init = (st & initMask) >> 4;
  timer_mode = (st & modeMask) >> 1;
  timer_nullcount = (st & BIT(6)) >> 6;
  timer_output = (st & BIT(7)) >> 7;

  //Dealing with bit 4 that must be ignored at times(timer_mode cannot exceed 5)
  if(timer_mode == 7 || timer_mode == 6) timer_mode -= 4;
  //printf("\n");
  //printf("-------------Timer %u -------------\n",timer);
  //printf("------------Status : %.8s\n",to_binary(8,st) );
  //Display timer config based in which info is requested by the user
  switch(field){
    case tsf_all:
      /*printf("------------Output : %u\n",timer_output);
      printf("--------Null Count : %u\n",timer_nullcount);
      printf("------Counter init : %u\n",timer_init);
      printf("---Programmed mode : %s(%u)\n",mode0[timer_mode],timer_mode);
      printf("-----Counting base : %s(%u)\n",basi[timer_base],timer_base);*/
      fieldVal.byte = st;
      timer_print_config(timer,tsf_all,fieldVal);
      break;
    case tsf_initial:
      //printf("------Counter init : %u\n",timer_init);
      fieldVal.in_mode = timer_init;
      timer_print_config(timer,tsf_initial,fieldVal);
      break;
    case tsf_mode:
      //printf("---Programmed mode : %s(%u)\n", mode0[timer_mode],timer_mode);
      fieldVal.count_mode = timer_mode;
      timer_print_config(timer,tsf_mode,fieldVal);
      break;
    case tsf_base:
      //printf("-----Counting base : %s(%u)\n",basi[timer_base],timer_base );
      fieldVal.bcd = timer_base;
      timer_print_config(timer,tsf_base,fieldVal);
      break;
    default:
      //Since enum elements correspond to integers,integers out of range may be
      //passed as the function's arguments
      //printf("ERR: INVALID FIELD VARIABLE----TERMINATING NOW----\n");
      return 2;
      break;
  }
  return 0;

}