Add vga-sync

2 files changed, 113 insertions, 0 deletions

diff --git a/vga-sync/lib/.holder b/vga-sync/lib/.holder
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/vga-sync/lib/.holder
diff --git a/vga-sync/src/sketch.ino b/vga-sync/src/sketch.ino
new file mode 100644
index 0000000..9bfafa0
--- /dev/null
+++ b/vga-sync/src/sketch.ino
@@ -0,0 +1,113 @@
+/* VGA Sync Generator
+ * 11/11/08 - dwan : dwanafite@yahoo.fr
+ *
+ * Based on :
+ *  - RG Matrix Example v.2 8/1/08, by BroHogan, from the Arduino Playground
+ *  - Simplest universal VGA/PAL terminal, by Ibragimov Maxim Rafikovich, http://www.vga-avr.narod.ru/main.html
+ *  - the very useful Timer/Counter/Prescaler Calculator, http://www.et06.dk/atmega_timers/
+ *  - Arduino.cc Port Manipulation Tutorial
+ *
+ * This program outputs pretty accurate VGA syncronization signals. It's using a timer interrupt on timer2, so hopefully you can make other cool things in loop().
+ */
+
+// 640 * 480 @ 60Hz - FvSync = 60.3 Hz / FhSync = 31.3 kHz
+// HSync : pin 7 Arduino, pin 13 VGA
+// VSync : pin 6 Arduino, pin 14 VGA
+// Arduino's pin 5 is HIGH when video can be sent, LOW otherwise. I use it to power a transistor. See this wonderful page : http://www.anatekcorp.com/driving.htm
+// 1 NOP = 62,5 ns wasted
+
+#define NOP asm("nop")
+
+#define vga_field_line_count 525         // number of VGA lines
+#define ISR_FREQ 0x3F                    // Sets the speed of the ISR - LOWER IS FASTER - 62
+
+volatile unsigned int linecount;
+
+void setup()
+{
+  //Serial.begin(9600);         // set up Serial library at 9600 bps
+  DDRD |= B11100000;            // it sets pins 7, 6 and 5 as output without changing the value of pins 0 & 1, which are RX & TX
+  //       76543210 <- pin translation
+
+  PORTD |= B11000000;   // sets pins 7 (hSync) and 6 (vSync) HIGH
+  //        76543210;
+  
+  setISRtimer();                        // setup the timer
+  startISR();                           // start the timer to toggle shutdown
+}
+
+void loop()
+{ 
+ 
+}
+
+///////////////////////////// ISR Timer Functions ///////////////////////////
+ISR(TIMER2_COMPA_vect)
+{
+        // Stop video
+        // pin 5 LOW
+        PORTD &= ~(1 << 5);
+        
+        // Front porch
+        NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+        
+        
+        // Count number of lines
+    if (++linecount == vga_field_line_count)
+    {
+    linecount = 0;
+    }
+
+    // can it be vsync tiem nao ?
+    if ((linecount == 10 )||(linecount == 11 ))
+    {
+        // hsync LOW
+        // vsync LOW
+        PORTD &= ~(1 << 7);
+        PORTD &= ~(1 << 6);
+    }
+    else    // ,hsync only
+    {
+        // hsync LOW
+        // vsync HIGH
+        PORTD &= ~(1 << 7);
+        PORTD |= (1 << 6);
+    }
+    
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+       
+        // nonetheless,
+    // hsync HIGH
+    PORTD |= (1 << 7); 
+    
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+    NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP; NOP;
+    NOP;
+    
+    // Start video if we are in a visible area
+        if (linecount > 45)
+        {
+        // pin 5 HIGH
+        PORTD |= (1 << 5);
+        }
+}
+
+void setISRtimer(){  // setup ISR timer controling toggleing
+  TCCR2A = 0x02;                        // WGM22=0 + WGM21=1 + WGM20=0 = Mode2 (CTC)
+  TCCR2B = (1 << CS01);                 // /8 prescaler (2MHz)
+  TCNT2 = 0;                            // clear counter
+  OCR2A = ISR_FREQ;                     // set TOP (divisor) - see #define
+}
+
+void startISR(){  // Starts the ISR
+  TCNT2 = 0;                            // clear counter (needed here also)
+  TIMSK2|=(1<<OCIE2A);                  // set interrupts=enabled (calls ISR(TIMER2_COMPA_vect)
+}
+
+void stopISR(){    // Stops the ISR
+  TIMSK2&=~(1<<OCIE2A);                  // disable interrupts
+}