From 9eaf78d6b5f4ce183d92b68c9f07b0d5363d2b06 Mon Sep 17 00:00:00 2001
From: giomba <giomba@glgprograms.it>
Date: Sat, 3 Jul 2021 15:02:01 +0200
Subject: [PATCH] introduced line buffer of 160 pixel

---
 const.h |  1 +
 main.S  | 31 ++++++++++++-------------------
 main.c  |  9 +++++++++
 3 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/const.h b/const.h
index fe2112f..95d854d 100644
--- a/const.h
+++ b/const.h
@@ -2,3 +2,4 @@
 
 #define VERTICAL_OFFSET 30
 #define HORIZONTAL_OFFSET 192
+#define LINE_BUFFER_SIZE 160
diff --git a/main.S b/main.S
index d1dbfe2..ff513ee 100644
--- a/main.S
+++ b/main.S
@@ -43,6 +43,8 @@ main:
     ldi r16, 1
     sts line, r16
 
+    call main_c
+
     sei                 ; global interrupt enable
 
 1:
@@ -94,6 +96,8 @@ int_timer_0:
     push r31
     in r31, IO(SREG)
     push r31
+    push r30
+    push r29
 
     ; turn off interrupt
     lds r31, TIMSK0
@@ -101,28 +105,17 @@ int_timer_0:
     sts TIMSK0, r31
 
     ; draw things
-    lds r31, frame
-    andi r31, 0x70
-    cpi r31, 0
-    breq 2f
-1:
-    dec r31
-    brne 1b
-2:
+    ldi r30, lo8(line_buffer)
+    ldi r31, hi8(line_buffer)
 
-    sbi IO(PORTB), 4
+.rept LINE_BUFFER_SIZE
+    ld r29, z+
+    out IO(PORTB), r29
     nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    cbi IO(PORTB), 4
+.endr
 
+    pop r29
+    pop r30
     pop r31
     out IO(SREG), r31
     pop r31
diff --git a/main.c b/main.c
index c7dfacf..027d9fe 100644
--- a/main.c
+++ b/main.c
@@ -1,5 +1,8 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include "const.h"
+
+char line_buffer[LINE_BUFFER_SIZE];
 
 ISR(INT0_vect, ISR_NAKED) {
     asm("jmp int_vertical_sync");
@@ -10,3 +13,9 @@ ISR(INT1_vect, ISR_NAKED) {
 ISR(TIMER0_COMPA_vect, ISR_NAKED) {
     asm("jmp int_timer_0");
 }
+
+void main_c() {
+    for (int i = 0; i < LINE_BUFFER_SIZE; ++i) {
+        line_buffer[i] = (i % 2) ? 0x0 : 0xff;
+    }
+}