55 lines
1.2 KiB
C
55 lines
1.2 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;
|
|
|
|
ISR(INT0_vect, ISR_NAKED) {
|
|
// vertical sync interrupt
|
|
asm("jmp int_vertical_sync");
|
|
}
|
|
ISR(INT1_vect, ISR_NAKED) {
|
|
// horizontal sync interrupt
|
|
asm("jmp int_horizontal_sync");
|
|
}
|
|
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();
|
|
}
|