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/*
* floppy.c
*
* Created: 29.04.2017 17:06:37
* Author: Jonas
*/
#include "floppy.h"
ISR(TIMER0_OVF_vect)
{
cli();
timer_overflow_counter ++;
*fPORT = 0xff; //Deactivate all previously activated pins
for(uint8_t i = 0; i < 8; i++) //Perform check of every channel
{
if(floppy_nextrun[i] == timer_overflow_counter && floppy_frequencies[i] > 0) //check if pulse is due
{
floppy_nextrun[i] += floppy_frequencies[i]; //set next pulse
floppy_pulse(i);
}
}
sei();
}
void floppy_setup(unsigned char *_pulse_port, unsigned char *_pulse_ddr, unsigned char *_direction_port, unsigned char *_direction_ddr)
{
//Setup Ports
fPORT = _pulse_port;
fDDR = _pulse_ddr;
dPORT = _direction_port;
dDDR = _direction_ddr;
//Floppy inputs are active low so they are initialized high
*fDDR = 0xff;
*fPORT = 0xff;
*dDDR = 0xff;
*dPORT = 0xff;
//Variable init
timer_overflow_counter = 0;
for(uint8_t i = 0; i < 8; i++)
{
floppy_head_return_counter[i] = 0;
floppy_frequencies[i] = 0;
floppy_nextrun[i] = 0;
}
//Return all FDDs to track 0
for(uint8_t i = 0; i < 200; i++)
{
_delay_ms(5);
*fPORT ^= 0xff;
}
*dPORT = 0x00; //Head needs to be reversed
*fPORT = 0xff;
//Setup Timer
TCCR0 |= (1 << CS01); // Prescaler 8 To leave enough time for ISR to complete
TIMSK |= (1 << TOIE0); //Activate Interrupt
sei();
}
void floppy_set_frequency(uint8_t _floppy_id, uint8_t _freq)
{
floppy_frequencies[_floppy_id] = _freq;
floppy_nextrun[_floppy_id] = _freq + timer_overflow_counter;
}
void floppy_pulse(uint8_t _floppy_id)
{
*fPORT &= ~(1 << _floppy_id); //Activate pin
floppy_head_return_counter[_floppy_id] ++;
if(floppy_head_return_counter[_floppy_id] > 75) //Toggle direction pin if more than 75 steps performed
{
*dPORT ^= (1<<_floppy_id);
floppy_head_return_counter[_floppy_id] = 0;
}
}
uint8_t floppy_calc_freq(uint32_t _f_hz)
{
///TODO Shift notes out of effective range of FDD into range
if(_f_hz < 31)
return 255;
if(_f_hz > 7813)
return 1;
return 7913 / _f_hz;
}
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