From 51fdaab28da64239ab9e4ce09c9f6eb17742d258 Mon Sep 17 00:00:00 2001
From: giomba <giomba@glgprograms.it>
Date: Thu, 3 Nov 2022 20:51:18 +0100
Subject: [PATCH] Add bouncing sprite. First experiment.

---
 const.h                   |   2 +-
 main.S                    |  49 ++++++++++----------------------------
 main.c                    |  39 +++++++++++++++++++++++++-----
 samples/bouncing-logo.pbm |  40 +++++++++++++++++++++++++++++++
 samples/bouncing-logo.xcf | Bin 0 -> 2871 bytes
 5 files changed, 87 insertions(+), 43 deletions(-)
 create mode 100644 samples/bouncing-logo.pbm
 create mode 100644 samples/bouncing-logo.xcf

diff --git a/const.h b/const.h
index 51c8eb5..382873f 100644
--- a/const.h
+++ b/const.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #define VERTICAL_OFFSET 30
-#define HORIZONTAL_OFFSET 192
+#define HORIZONTAL_OFFSET 168
 #define LINE_BUFFER_SIZE 160
 
 #define BLACK 0x00
diff --git a/main.S b/main.S
index 15e2fd5..e6b5978 100644
--- a/main.S
+++ b/main.S
@@ -36,29 +36,14 @@ main_asm:
 1:
     rjmp 1b
 
-.global int_horizontal_sync
-int_horizontal_sync:    ; +3
-    push r31            ; +5
-    in r31, IO(SREG)    ; +6, status register
-    push r31            ; +8
-    push r30            ; +10
+.global int_horizontal_sync_s
+int_horizontal_sync_s:
+    push r31
 
-    ; if (0 <= line < 256), then enter
-    lds r30, line       ; +12
-    lds r31, line + 1   ; +14
-    adiw z, 1           ; +16
-    sts line, r30       ; +18
-    sts line + 1, r31   ; +20
-    cpi r31, 0          ; +21
-    breq enter          ; +23
-    jmp int_horizontal_sync_end
-
-enter:
-    ; here, +23 cycles have passed since horizontal sync
-    ; so, there are still ~168 cycles before first useful data
+    ; load timer to trigger isr at the beginning of the visible scanline
     ldi r31, 0
     sts TCNT0, r31
-    ldi r31, HORIZONTAL_OFFSET  ; set counter TOP
+    lds r31, hpos       ; set counter TOP
     sts OCR0A, r31
 
     ldi r31, 0x7        ; clear any pending interrupt
@@ -68,12 +53,8 @@ enter:
     ori r31, 0x02       ; mask enable interrupt timer A
     sts TIMSK0, r31
 
-int_horizontal_sync_end:
-    pop r30
     pop r31
-    out IO(SREG), r31
-    pop r31
-    reti
+    ret
 
 .global int_timer_0
 int_timer_0:
@@ -83,6 +64,7 @@ int_timer_0:
     push r31
     push r30
     push r29
+    push r25
 
     ; turn off interrupt
     lds r31, TIMSK0
@@ -96,11 +78,11 @@ int_timer_0:
     lds zl, current_jump_table
     lds zh, current_jump_table + 1
 
-;    ldi zl, pm_lo8(line_jump_table_0)
-;    ldi zh, pm_hi8(line_jump_table_0)
-
     clr r0
     lds r29, line
+    lds r25, vpos
+    sub r29, r25
+
     add zl, r29
     adc zh, r0
     add zl, r29
@@ -110,6 +92,7 @@ int_timer_0:
 
 .global jump_table_return_address
 jump_table_return_address:
+    pop r25
     pop r29
     pop r30
     pop r31
@@ -117,8 +100,8 @@ jump_table_return_address:
     pop r31
     reti
 
-.global int_vertical_sync
-int_vertical_sync:
+.global int_vertical_sync_s
+int_vertical_sync_s:
     push r31
     in r31, IO(SREG)
     push zl
@@ -126,12 +109,6 @@ int_vertical_sync:
     push yl
     push yh
 
-    lds r31, frame + 1
-    lds r30, frame
-    adiw z, 1
-    sts frame + 1, r31
-    sts frame, r30
-
     ldi r30, 1
     ldi r31, 0
     sts line, r30
diff --git a/main.c b/main.c
index c3ac480..a07a29e 100644
--- a/main.c
+++ b/main.c
@@ -18,14 +18,41 @@ 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");
+// 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();
 }
-ISR(INT1_vect, ISR_NAKED) {
-  // horizontal sync interrupt
-  asm("jmp int_horizontal_sync");
+
+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");
diff --git a/samples/bouncing-logo.pbm b/samples/bouncing-logo.pbm
new file mode 100644
index 0000000..126dd94
--- /dev/null
+++ b/samples/bouncing-logo.pbm
@@ -0,0 +1,40 @@
+P1
+# Created by GIMP version 2.10.32 PNM plug-in
+40 64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\ No newline at end of file
diff --git a/samples/bouncing-logo.xcf b/samples/bouncing-logo.xcf
new file mode 100644
index 0000000000000000000000000000000000000000..1054ca8fbe8f8c5959ceea7fe3922b31860ae307
GIT binary patch
literal 2871
zcmcguU1%It6h5;%Bu(0wjYgvo;dc9D`mk{~smVsRX>F29D77JxBAAD4c4s%Eo1Hj2
zu^S(ZF9D&i8$~R{g7_eUqEst{)(6oC!Ka9z2tvC)7GjcaZ8KTFb7wY8mu?n(@a~*D
z-#y>C=YIFhok`OA?3~CaQsT{UBtmFiuu}}s-h;Kl6b0R5uzf=x5e;{q0;G1B3iHFB
za52X{4%>jWq>(z5FlJ}9tc5W#`RI_T#Vsu<F6!2dcyaXH7&8GGs?WyLS}1MmN%nE{
zXI(jKA)|?$k<pXKn!8fzgpn~!(IsyoGd&#_Vfl+313mo^IwItc>3nW3p3t*t5eZ|o
z@W99&gyyrlCG>1!M$7RGBbCZ&mXPrt?7#<uS+l1prZZ?b=y6uyGXN)GyvLUDk(bBM
zpE)x+H2TsD9MAycx|U%)Sv~m<dek1qer`>$3J!X3rw2ECu<+ph9(=%qTRgZGnAhXR
zA{$}69_K&eV%+F3<1!lVhdkJOHgF!4@4z_^+0yb>C=*}MWPOlZ`M7H~ZoWQ0CxS5t
z494&@vLa<<trL^M3q#}L{KT+0XJn1Z;4WusY15d`CJ}KcEZZ)b)8EqIj`R%l!{;q;
z>{-q{SbcMs4dRLOq9Qn9%$o^K3>isHjG2ZwZDf)aHpJ;g&v7?c4xN)Qr{}c{ADejA
z(&HIDo)Zi57-izw^gPbC2<lcyw>Z;uJg0?{x~U~B-N=fJWx`o~xSg}jNB6b)oTaB0
zL;|mp#-Y<jJ~YenQdpE<4R&1AlX$6mqur7IX!yC_Xm7Zur@#MrpG(hZdV0nZec|r#
zz(6D%1>e`-AMJ^{ygd86o0!qD3%o3H3wV6qrk?bSDu>xUkLs%r;owqp75`$>S*qAk
zQUV*k)<CPg8X5u(9i)^u&Tf|P%Infn`BDe1Pe1j^vg-FQ`<K<#Rduz4wx?RJ6nu2I
zKn3~&T?gI1^_zBcZ5-p9Yggd8u=Ybc-M;$GzE5Kva9;hj6V4}N(RSLN{`Rmt_uW@k
zXa)JFPJi(8<@XU*X#errW#nHE(TJJ1XoP>EeD@&h+z*jZ=v-3gHHe%lCm|9&>r{Qv
zsVplHiJo;5VXc3VnOd+u-MO{)v?CMl`vsCR?<~b!nU2$uxjS`*-r%Y0>>zsnml!0X
zmnxx;pwGF6>3$Qw4NV8>9u{o=>42bnUsGXmbqV0_^M&ipHvm4r{vlX^!rOoS@%^6+
z0>6Jb_7wvvI23k`Yf)X}hvxm0&^UotBx$hQ#~oU|4;Ftw{?88<Yx=JrtjeA^2U;U<
zz0xXW;6He1jl<4e_7#r(lNG;@l%kKyuK9`zsl`X&v#Ch_;wBY~^5QN4vIgM?p^%Sf
zA(K+vt`lD~(VoN($>dv7k<>+P#WEe;(-b-aY4xl+$D;p6Ro2=W8mP0V;-o1h6w)<c
z356`7kR_W+<S%VfsU$D%0w8M;C?rT9&q5}pv|T5@W}-cb9g@knq#~({+Da(oo`xbq
zT0N`IfkIYgt(^gdEXhLJD5PsX8-=t{NZTfx{Prd>V2myRvIc=dg7nE?6w=<V6JImY
mp2QA8rebeZMA`UX)J7rqG!zli>RELT6tXI7?F=ZSt<t{|_eV$o

literal 0
HcmV?d00001