82 lines
1.7 KiB
C
82 lines
1.7 KiB
C
/**
|
|
* @file main.c
|
|
* @author giomba@glgprograms.it
|
|
* @brief OSDY main.
|
|
*
|
|
* @copyright Copyright RetrOfficina GLG Programs (c) 2022
|
|
*
|
|
* Video image generator superimposition for analog PAL signals,
|
|
* with Atmega328, for your retro OSD titles.
|
|
*
|
|
*/
|
|
#include "const.h"
|
|
#include <avr/interrupt.h>
|
|
#include <avr/io.h>
|
|
#include <string.h>
|
|
|
|
volatile uint16_t frame = 0;
|
|
volatile uint16_t line = 0xfe;
|
|
volatile uint8_t image = 0xff;
|
|
|
|
// horizontal and vertical position of bouncing logo
|
|
volatile uint8_t vpos = 0;
|
|
volatile uint8_t hpos = 0;
|
|
volatile int8_t vinc = +1;
|
|
volatile int8_t hinc = +1;
|
|
|
|
void int_vertical_sync_s(void);
|
|
ISR(INT0_vect) {
|
|
frame += 1;
|
|
vpos += vinc;
|
|
hpos += hinc;
|
|
|
|
if (vpos == 0)
|
|
vinc = +1;
|
|
if (vpos == 256 - 64)
|
|
vinc = -1;
|
|
if (hpos == HORIZONTAL_OFFSET)
|
|
hinc = +1;
|
|
if (hpos == 255 - 40)
|
|
hinc = -1;
|
|
|
|
int_vertical_sync_s();
|
|
}
|
|
|
|
void int_horizontal_sync_s(void);
|
|
ISR(INT1_vect) {
|
|
line += 1;
|
|
// if (line >= 256)
|
|
if (line >= vpos + 64)
|
|
return;
|
|
|
|
if (line >= vpos)
|
|
int_horizontal_sync_s();
|
|
}
|
|
|
|
ISR(TIMER0_COMPA_vect, ISR_NAKED) {
|
|
// back porch timer interrupt
|
|
asm("jmp int_timer_0");
|
|
}
|
|
|
|
// external assembly main loop
|
|
void main_asm(void);
|
|
|
|
int main() {
|
|
// port B, pin 4 and 5 as output, others as input
|
|
DDRB |= 0x30;
|
|
|
|
// set interrupt vectors at address 0x0, not bootloader
|
|
// timing is important, see atmel datasheet
|
|
_SFR_IO8(MCUCR) = (1 << IVCE);
|
|
_SFR_IO8(MCUCR) = 0;
|
|
|
|
EICRA = 0x0a; // external interrupt 0 and 1, falling edge
|
|
EIMSK = 0x03; // external interrupt 0 and 1, mask enable
|
|
|
|
TCCR0A = 0x02; // don't connect output pins to timer, CTC[1:0] mode
|
|
|
|
TCCR0B = 0x01; // CTC[2] mode, no prescaler
|
|
|
|
main_asm();
|
|
}
|