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videochargen
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Use 16bit TIMER1 to sweep more horizontally.

This commit is contained in:
giomba 2022-11-03 22:05:59 +01:00
parent 51fdaab28d
commit b76ec5e498
2 changed files with 28 additions and 14 deletions
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30
main.S
View File

@ -39,20 +39,30 @@ main_asm:
.global int_horizontal_sync_s
int_horizontal_sync_s:
push r31
push r30
; load timer to trigger isr at the beginning of the visible scanline
; reset counter to 0
ldi r31, 0
sts TCNT0, r31
lds r31, hpos ; set counter TOP
sts OCR0A, r31
sts TCNT1H, r31
sts TCNT1L, r31
ldi r31, 0x7 ; clear any pending interrupt
sts TIFR0, r31
; set counter TOP (MSB first!)
lds r31, hpos + 1
lds r30, hpos
sts OCR1AH, r31
sts OCR1AL, r30
lds r31, TIMSK0
ori r31, 0x02 ; mask enable interrupt timer A
sts TIMSK0, r31
; clear any pending interrupt
ldi r31, 0x7
sts TIFR1, r31
; enable interrupt timer A
lds r31, TIMSK1
ori r31, 0x02
sts TIMSK1, r31
pop r30
pop r31
ret
@ -67,9 +77,9 @@ int_timer_0:
push r25
; turn off interrupt
lds r31, TIMSK0
lds r31, TIMSK1
andi r31, 0xfd ; mask disable interrupt timer A
sts TIMSK0, r31
sts TIMSK1, r31
lds r31, show_image
cpi r31, 0x1

12
main.c
View File

@ -20,7 +20,7 @@ volatile uint8_t image = 0xff;
// horizontal and vertical position of bouncing logo
volatile uint8_t vpos = 0;
volatile uint8_t hpos = 0;
volatile uint16_t hpos = 0;
volatile int8_t vinc = +1;
volatile int8_t hinc = +1;
@ -36,7 +36,7 @@ ISR(INT0_vect) {
vinc = -1;
if (hpos == HORIZONTAL_OFFSET)
hinc = +1;
if (hpos == 255 - 40)
if (hpos == 1024 - 80)
hinc = -1;
int_vertical_sync_s();
@ -53,7 +53,7 @@ ISR(INT1_vect) {
int_horizontal_sync_s();
}
ISR(TIMER0_COMPA_vect, ISR_NAKED) {
ISR(TIMER1_COMPA_vect, ISR_NAKED) {
// back porch timer interrupt
asm("jmp int_timer_0");
}
@ -73,9 +73,13 @@ int main() {
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
TCCR1A = 0x00; // don't connect output pins to timer, CTC[1:0] mode
TCCR1B = 0x09; // CTC[3:2] mode, no prescaler
#if 0
TCCR0A = 0x02; // don't connect output pins to timer, CTC[1:0] mode
TCCR0B = 0x01; // CTC[2] mode, no prescaler
#endif
main_asm();
}