Finally a stable 640x480.

src/main.c

@@ -114,11 +114,26 @@ void setup_clocks(void)
 static bool dma_ready = false;
 static int dma_channel;
 
+/**
+ * @brief Represents a program running on the SM of a PIO.
+ *
+ */
+typedef struct PIORun
+{
+	PIO pio;     //< executing PIO
+	uint offset; //< PIO memory offset for program
+	uint sm;     //< executing SM
+} PIORun;
+
+PIORun *vga_pixel_ptr = NULL;
+
 void new_frame_handler(void)
 {
-	// restart DMA
-	if (dma_ready)
-		dma_channel_set_read_addr(dma_channel, &frames[0].data[0], true);
+	if (vga_pixel_ptr && dma_ready)
+	{
+		pio_sm_put_blocking(vga_pixel_ptr->pio, vga_pixel_ptr->sm, 0);
+		dma_channel_set_read_addr(dma_channel, &frames[0].data[4], true);
+	}
 
 	pio_interrupt_clear(pio0_hw, 1);
 }
@@ -134,16 +149,21 @@ void set_pixel(uint16_t x, uint16_t y)
 	frames[0].data[y * 80 + x / 8] |= (1 << x % 8);
 }
 
-/**
- * @brief Represents a program running on the SM of a PIO.
- *
- */
-typedef struct PIORun
+void clear_pixel(uint16_t x, uint16_t y)
 {
-	PIO pio;     //< executing PIO
-	uint offset; //< PIO memory offset for program
-	uint sm;     //< executing SM
-} PIORun;
+	frames[0].data[y * 80 + x / 8] &= ~(1 << x % 8);
+}
+
+void draw_simple_line(uint16_t x, uint16_t y, uint16_t len, bool horizontal)
+{
+	for (uint16_t i = 0; i < len; ++i)
+	{
+		if (horizontal)
+			set_pixel(x + i, y);
+		else
+			set_pixel(x, y + i);
+	}
+}
 
 int main()
 {
@@ -157,17 +177,33 @@ int main()
 	// horizontal lines
 	for (uint16_t x = 0; x < 639; ++x) // last pixel high -> bad
 	{
-		set_pixel(x, 0);
+		if ((x / 32) % 2 == 0)
+			set_pixel(x, 20);
+		if ((x / 32) % 2 == 1)
+			set_pixel(x, 23);
 		set_pixel(x, 239);
 		set_pixel(x, 479);
 	}
 	// vertical lines
-	for (uint16_t y = 0; y < 480; ++y)
+	for (uint16_t y = 21; y < 480; ++y)
 	{
+		set_pixel(0 + ((y - 20) / 10) * 4, y);
 		set_pixel(0, y);
-		set_pixel(239, y);
+		set_pixel(319, y);
 		set_pixel(638, y);
 	}
+	// try to find strangeness using stairs
+	for (uint16_t x = 0; x < 639; ++x)
+	{
+		set_pixel(x, (x / 32) * 4 + 120);
+	}
+	// draw "E" - nice because it's not symmetrical along X
+	draw_simple_line(100, 100, 8, true);
+	draw_simple_line(100, 100, 8, false);
+	draw_simple_line(100, 104, 8, true);
+	draw_simple_line(100, 108, 8, true);
+
+	clear_pixel(639, 479);
 
 	// Running programs on PIO
 	PIORun vga_hsync, vga_vsync, vga_pixel;
@@ -188,8 +224,8 @@ int main()
 	vga_hsync.sm = pio_claim_unused_sm(vga_hsync.pio, true);
 	vga_hsync_program_init(vga_hsync.pio, vga_hsync.sm, vga_hsync.offset);
 	// low pulse is X pixels long, and SM runs at 4x of pixel clock
-	pio_sm_put_blocking(vga_hsync.pio, vga_hsync.sm, (64 - 1));
-	pio_sm_put_blocking(vga_hsync.pio, vga_hsync.sm, (640 - 1));
+	pio_sm_put_blocking(vga_hsync.pio, vga_hsync.sm, (64 - 2));
+	pio_sm_put_blocking(vga_hsync.pio, vga_hsync.sm, (640 + 16 - 1)); // 16 is front porch
 	printf("OK\n");
 
 	// VGA VSYNC program
@@ -205,6 +241,7 @@ int main()
 	printf("OK\n");
 
 	// VGA pixel program
+	vga_pixel_ptr = &vga_pixel;
 	printf("Starting VGA pixel machine... ");
 	if (!pio_can_add_program(vga_pixel.pio, &vga_free_run_program))
 		panic("cannot add program");
@@ -227,8 +264,8 @@ int main()
 	irq_set_exclusive_handler(DMA_IRQ_0, dma_handler);
 	irq_set_enabled(DMA_IRQ_0, true);
 
-	dma_channel_configure(dma_channel, &dma_config, &pio0_hw->txf[2], &frames[0].data[0], 9600,
-	                      false);
+	dma_channel_configure(dma_channel, &dma_config, &pio0_hw->txf[2], &frames[0].data[0], 9600 - 1,
+	                      true);
 
 	dma_ready = true;
 	printf("OK\n");

src/vga.pio

@@ -8,7 +8,7 @@ entrypoint_vga_free_run:
     mov x, y
     wait irq 7
 loop:
-    out pins, 1 [3]
+    out pins, 1 [2]
     jmp x-- loop
 .wrap
 
@@ -27,10 +27,9 @@ hsync_pulse:
     jmp x-- hsync_pulse [3]
 
     set pins, 1 [1]
-    set y, 24
+    set y, 27
 hsync_back_porch:
-    jmp y-- hsync_back_porch [19]
-
+    jmp y-- hsync_back_porch [16]
     irq set 7
 
     mov x, osr [3]
@@ -53,11 +52,12 @@ vsync_pulse:
     set pins, 0
     jmp x-- vsync_pulse
 
+    irq set 1
+
     mov x, osr
 vsync_idle:
     wait irq 0
     set pins, 1
     jmp x-- vsync_idle
 
-    irq set 1
 .wrap