updated leaf demo

1 files changed, 116 insertions, 62 deletions

diff --git a/examples/vga-leaf.cpp b/examples/vga-leaf.cpp
index db20eb2..16204ba 100644
--- a/examples/vga-leaf.cpp
+++ b/examples/vga-leaf.cpp
@@ -1,13 +1,48 @@
-// Low-level, non-wirish demonstration of VGA
+/*
+ Crude VGA Output
+
+ Outputs a red and white leaf to VGA. This implementation is crude and noisy,
+ but a fun demo. It should run most VGA monitors at 640x480, though it does
+ not follow the timing spec very carefully. Real twisted or shielded wires,
+ proper grounding, and not doing this on a breadboard are recommended (but
+ it seems to work ok without).
+
+ SerialUSB is disabled to get rid of most interrupts (which mess with timing);
+ the SysTick is probably the source of the remaining flickers. This means that
+ you have to use perpetual bootloader or the reset button to flash new 
+ programs.
+
+ How to wire this to a VGA port:
+    D5 via ~200ohms to VGA Red     (1)
+    D6 via ~200ohms to VGA Green   (2)
+    D7 via ~200ohms to VGA Blue    (3)
+    D11 to VGA VSync               (14)  (swapped?)
+    D12 to VGA HSync               (13)  (swapped?)
+    GND to VGA Ground              (5)
+    GND to VGA Sync Ground         (10)
+
+ See also:
+  - http://pinouts.ru/Video/VGA15_pinout.shtml
+  - http://www.epanorama.net/documents/pc/vga_timing.html
+ 
+ Created 20 July 2010
+ By Bryan Newbold for LeafLabs
+ This code is released with no strings attached.
+ 
+ */
 
 #include "wirish.h"
 
 #define LED_PIN 13
-#define VGA_R 5     // B6
-#define VGA_G 6     // A8
-#define VGA_B 7     // A9
-#define VGA_V 11    // A6
-#define VGA_H 12    // A7
+
+// Pinouts
+#define VGA_R 5     // STM32: B6
+#define VGA_G 6     // STM32: A8
+#define VGA_B 7     // STM32: A9
+#define VGA_V 11    // STM32: A6
+#define VGA_H 12    // STM32: A7
+
+// These low level macros make GPIO writes much faster
 #define VGA_R_HIGH (GPIOB_BASE)->BSRR = BIT(6)
 #define VGA_R_LOW  (GPIOB_BASE)->BRR  = BIT(6)
 #define VGA_G_HIGH (GPIOA_BASE)->BSRR = BIT(8)
@@ -24,65 +59,95 @@ void isr_start(void);
 void isr_stop(void);
 void isr_update(void);
 
-void setup()
-{
+uint8 toggle;
+uint16 x = 0;       // X coordinate
+uint16 y = 0;       // Y coordinate
+uint8 v_active = 1; // Are we in the image?
+
+// 1-bit!
+uint8 logo[18][16] = {
+    {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,},
+    {0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,},
+    {0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,},
+    {0,0,0,0,1,0,0,1,0,0,1,0,0,0,0,0,},
+    {0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,0,},
+    {0,0,1,0,0,0,0,1,0,0,0,0,1,0,0,0,},
+    {0,0,1,0,0,1,0,1,0,1,0,0,1,0,0,0,},
+    {0,1,0,0,0,0,1,1,1,0,0,0,0,1,0,0,},
+    {0,1,0,1,0,0,0,1,0,0,0,1,0,1,0,0,},
+    {1,0,0,0,1,0,0,1,0,0,1,0,0,0,1,0,},
+    {1,0,0,0,0,1,0,1,0,1,0,0,0,0,1,0,},
+    {1,0,0,0,0,0,1,1,1,0,0,0,0,0,1,0,},
+    {0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,},
+    {0,0,1,1,0,0,0,1,0,0,0,1,1,0,0,0,},
+    {0,0,0,0,1,1,1,0,1,1,1,0,0,0,0,0,},
+    {0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,},
+    {0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,},
+    {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,}, };
+
+void setup() {
+    
+    // Setup our pins
     pinMode(LED_PIN, OUTPUT);
-    digitalWrite(LED_PIN, 1);
     pinMode(VGA_R, OUTPUT);
     pinMode(VGA_G, OUTPUT);
     pinMode(VGA_B, OUTPUT);
     pinMode(VGA_V, OUTPUT);
     pinMode(VGA_H, OUTPUT);
-
-    /* Send a message out USART2  */
-    Serial2.begin(9600);
-    Serial2.println("Video time...");
+    digitalWrite(VGA_R, LOW);
+    digitalWrite(VGA_G, LOW);
+    digitalWrite(VGA_B, LOW);
+    digitalWrite(VGA_H, HIGH);
+    digitalWrite(VGA_V, HIGH);
 
     // This gets rid of the majority of the interrupt artifacts;
     // a SysTick.end() is required as well
     SerialUSB.end();
     
-    digitalWrite(VGA_R, 0);
-    digitalWrite(VGA_G, 0);
-    digitalWrite(VGA_B, 0);
-    digitalWrite(VGA_H,1);
-    digitalWrite(VGA_V,1);
-
-    timer_set_prescaler(4,0);
-    timer_set_mode(4, 1, TIMER_OUTPUTCOMPARE);
-    timer_set_mode(4, 2, TIMER_OUTPUTCOMPARE);
-    timer_set_mode(4, 3, TIMER_OUTPUTCOMPARE);
-    timer_set_mode(4, 4, TIMER_OUTPUTCOMPARE);
-    timer_set_reload(4, 2287);
-    timer_set_compare_value(4,1,200);
-    timer_set_compare_value(4,2,300);
-    timer_set_compare_value(4,3,2170);  // 2219 max...
-    timer_set_compare_value(4,4,1);
-    timer_attach_interrupt(4,1,isr_porch);
-    timer_attach_interrupt(4,2,isr_start);
-    timer_attach_interrupt(4,3,isr_stop);
-    timer_attach_interrupt(4,4,isr_update);
-
-    timer_set_count(4,0);
+
+    // Configure
+    Timer4.pause(); // while we configure
+    Timer4.setPrescaleFactor(1);     // Full speed
+    Timer4.setChannel1Mode(TIMER_OUTPUTCOMPARE);
+    Timer4.setChannel2Mode(TIMER_OUTPUTCOMPARE);
+    Timer4.setChannel3Mode(TIMER_OUTPUTCOMPARE);
+    Timer4.setChannel4Mode(TIMER_OUTPUTCOMPARE);
+    Timer4.setOverflow(2287);   // Total line time
+
+    Timer4.setCompare1(200);
+    Timer4.attachCompare1Interrupt(isr_porch);
+    Timer4.setCompare2(300);
+    Timer4.attachCompare2Interrupt(isr_start);
+    Timer4.setCompare3(2170);
+    Timer4.attachCompare3Interrupt(isr_stop);
+    Timer4.setCompare4(1);      // Could be zero I guess
+    Timer4.attachCompare4Interrupt(isr_update);
+    
+    Timer4.setCount(0);         // Ready...
+    Timer4.resume();            // Go!
 }
 
 void loop() {
-    // everything happens in the interrupts!
+    toggle ^= 1;
+    digitalWrite(LED_PIN, toggle);
+    delay(100);
+
+    // Everything happens in the interrupts!
 }
 
-int toggle = 0;
-uint16 x = 0;
-uint16 y = 0;
-uint8 v_active = 1;
 
+// This ISR will end horizontal sync for most of the image and
+// setup the vertical sync for higher line counts
 void isr_porch(void) {
     VGA_H_HIGH;
     y++;
+    // Back to the top
     if(y>=523) {
         y=1;
         v_active = 1;
         return;
     }
+    // Other vsync stuff below the image
     if(y>=492) {
         VGA_V_HIGH;
         return;
@@ -91,37 +156,22 @@ void isr_porch(void) {
         VGA_V_LOW;
         return;
     }
-    if(y>=479) {    // 479
+    if(y>=479) { 
         v_active = 0;
         return;
     }
 }
 
-uint8 logo[18][16] = {
-    {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,},
-    {0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,},
-    {0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,},
-    {0,0,0,0,1,0,0,1,0,0,1,0,0,0,0,0,},
-    {0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,0,},
-    {0,0,1,0,0,0,0,1,0,0,0,0,1,0,0,0,},
-    {0,0,1,0,0,1,0,1,0,1,0,0,1,0,0,0,},
-    {0,1,0,0,0,0,1,1,1,0,0,0,0,1,0,0,},
-    {0,1,0,1,0,0,0,1,0,0,0,1,0,1,0,0,},
-    {1,0,0,0,1,0,0,1,0,0,1,0,0,0,1,0,},
-    {1,0,0,0,0,1,0,1,0,1,0,0,0,0,1,0,},
-    {1,0,0,0,0,0,1,1,1,0,0,0,0,0,1,0,},
-    {0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,},
-    {0,0,1,1,0,0,0,1,0,0,0,1,1,0,0,0,},
-    {0,0,0,0,1,1,1,0,1,1,1,0,0,0,0,0,},
-    {0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,},
-    {0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,},
-    {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,}, };
-
-void isr_start(void) {
+// This is the main horizontal sweep
+void isr_start(void) {  
+    // Skip if we're not in the image at all
     if(!v_active) { return; }
+
+    // Start Red
     VGA_R_LOW;
     VGA_R_HIGH;
 
+    // For each "pixel" (really 20 or so screen pixels?) go red or white
     for(x=0; x<32; x++) {
         if(logo[y/28][x/2]) {
             VGA_G_HIGH;
@@ -132,12 +182,16 @@ void isr_start(void) {
         }
     }
 }
+
+// End of the horizontal line
 void isr_stop(void) {
     if(!v_active) { return; }
     VGA_R_LOW;
     VGA_G_LOW;
     VGA_B_LOW;
 }
+
+// Setup horizonal sync
 void isr_update(void) {
     VGA_H_LOW;
 }