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Shorten dejitter code #24

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Shorten dejitter code #24

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279823d
Remove unused r17 and r21
miracoli Apr 25, 2021
5f1c071
Shorten dejitter code
miracoli Apr 24, 2021
1e01545
Fix #22
miracoli Apr 25, 2021
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58 changes: 22 additions & 36 deletions VGAX.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -100,41 +100,27 @@ ISR(TIMER2_OVF_vect) {
//interrupt jitter fix (needed to keep signal stable)
//code from https://github.com/cnlohr/avrcraft/tree/master/terminal
//modified from 4 nop align to 8 nop align
#define DEJITTER_OFFSET 1
#define DEJITTER_SYNC -2
asm volatile(
" lds r16, %[timer0] \n\t" //
#if defined(__AVR_ATmega2560__)
" add r16, %[toffset] \n\t" //
#endif
" subi r16, %[tsync] \n\t" //
" andi r16, 7 \n\t" //
" call TL \n\t" //
"TL: \n\t" //
#if defined(__AVR_ATmega2560__)
" pop r17 \n\t" //ATMEGA2560 has a 22bit PC!
#endif
" pop r31 \n\t" //
" pop r30 \n\t" //
" adiw r30, (LW-TL-5) \n\t" //
" add r30, r16 \n\t" //
//" adc r31, __zero_reg__ \n\t" //
" ijmp \n\t" //
"LW: \n\t" //
" nop \n\t" //
" nop \n\t" //
" nop \n\t" //
" nop \n\t" //
" nop \n\t" //
" nop \n\t" //
" nop \n\t" //
//" nop \n\t" //
"LBEND: \n\t" //
:
: [timer0] "i" (&TCNT0),
[toffset] "i" ((uint8_t)DEJITTER_OFFSET),
[tsync] "i" ((uint8_t)DEJITTER_SYNC)
: "r30", "r31", "r16", "r17");
#define DEJITTER_SYNC 9
{
uint8_t jitter;
asm volatile(
" lds %[jitter], %[timer0] \n\t" //
" subi %[jitter], %[tsync] \n\t" //
" andi %[jitter], 7 \n\t" //
" ldi ZL, pm_lo8(NOP_SLIDE) \n\t" //
" ldi ZH, pm_hi8(NOP_SLIDE) \n\t" //
" add ZL, %[jitter] \n\t" //
" adc ZH, __zero_reg__ \n\t" //
" ijmp \n\t" //
"NOP_SLIDE: \n\t" //
".rept 7 \n\t" //
" nop \n\t" //
".endr \n\t" //
: [jitter] "=d" (jitter)
: [timer0] "i" (&TCNT0),
[tsync] "i" ((uint8_t)DEJITTER_SYNC)
: "r30", "r31");
}
/*
Output all pixels.

Expand Down Expand Up @@ -178,7 +164,7 @@ ISR(TIMER2_OVF_vect) {
: [port] "I" (_SFR_IO_ADDR(PORTD)),
#endif
"z" "I" (/*rline*/(byte*)vgaxfb + rlinecnt*VGAX_BWIDTH)
: "r16", "r17", "r20", "r21", "memory");
: "r16", "r20", "memory");

//increment framebuffer line counter after 6 VGA lines
#if defined(__AVR_ATmega2560__) && defined(ATMEGA2560_MAXRES)
Expand Down
4 changes: 4 additions & 0 deletions VGAXUtils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,8 @@ class VGAXUtils {
//porting of TVOut::draw_rect method, writen by Myles Metzer
static inline void draw_rect(uint8_t x0, uint8_t y0, uint8_t w, uint8_t h,
uint8_t c, char fc) {
--w;
--h;
if (fc != -1) {
for (unsigned char i=y0; i < y0+h; i++) {
VGAXUtils::draw_row(i, x0, x0+w, fc);
Expand Down Expand Up @@ -288,6 +290,8 @@ class VGAXUtils {
//Safe version with screen clipping
static inline void draw_rect_safe(uint8_t x0, uint8_t y0, uint8_t w, uint8_t h,
uint8_t c, char fc) {
--w;
--h;
if (fc != -1) {
for (unsigned char i=y0; i < y0+h; i++) {
VGAXUtils::draw_row_safe(i, x0, x0+w, fc);
Expand Down