Stable VGA 640x460@75Hz. Black screen.

src/main.c

@@ -53,13 +53,30 @@ static void vga_pixel_program_init(PIO pio, uint sm, uint offset)
 	pio_sm_set_enabled(pio, sm, true);
 }
 
-static void vga_sync_program_init(PIO pio, uint sm, uint offset)
+static void vga_hsync_program_init(PIO pio, uint sm, uint offset)
 {
-	pio_sm_config config = vga_sync_program_get_default_config(offset);
+	pio_sm_config config = vga_hsync_program_get_default_config(offset);
 	// destination pins for SET instructions
-	sm_config_set_set_pins(&config, 20, 2);
+	sm_config_set_set_pins(&config, 20, 1);
 	pio_gpio_init(pio, 20);
-	pio_sm_set_consecutive_pindirs(pio, sm, 20, 2, true);
+	pio_sm_set_consecutive_pindirs(pio, sm, 20, 1, true);
+
+	pio_sm_init(pio, sm, offset, &config);
+
+	pio_sm_set_clkdiv_int_frac(pio, sm, 1, 0);
+
+	pio->sm->shiftctrl = (1 << PIO_SM0_SHIFTCTRL_FJOIN_TX_LSB);
+
+	pio_sm_set_enabled(pio, sm, true);
+}
+
+static void vga_vsync_program_init(PIO pio, uint sm, uint offset)
+{
+	pio_sm_config config = vga_vsync_program_get_default_config(offset);
+	// destination pins for SET instructions
+	sm_config_set_set_pins(&config, 21, 1);
+	pio_gpio_init(pio, 21);
+	pio_sm_set_consecutive_pindirs(pio, sm, 21, 1, true);
 
 	pio_sm_init(pio, sm, offset, &config);
 
@@ -98,31 +115,35 @@ int main()
 	printf("Starting VGA pixel machine on %u...\n", sm0);
 	vga_pixel_program_init(pio, sm0, offset0);
 
-	// VGA sync program
-	uint offset1 = pio_add_program(pio, &vga_sync_program);
+	// VGA HSYNC program
+	uint offset1 = pio_add_program(pio, &vga_hsync_program);
 	uint sm1 = pio_claim_unused_sm(pio, true);
 	printf("Starting VGA sync machine on %u...\n", sm1);
-	vga_sync_program_init(pio, sm1, offset1);
+	vga_hsync_program_init(pio, sm1, offset1);
+	printf("Feeding horizontal sync...\n");
+	// low pulse is X pixels long, and SM runs at 4x of pixel clock
+	pio_sm_put_blocking(pio, sm1, 64 * 4);
+	pio_sm_put_blocking(pio, sm1, 765 * 4);
 
-	printf("Welcome.\n");
+	// VGA VSYNC program
+	uint offset2 = pio_add_program(pio, &vga_vsync_program);
+	uint sm2 = pio_claim_unused_sm(pio, true);
+	printf("Starting VGA vsync machine on %u...\n", sm2);
+	vga_vsync_program_init(pio, sm2, offset2);
+	printf("Feeding vertical sync...\n");
+	// low pulse assert lasts for 3 horizontal lines, then adjust by one
+	pio_sm_put_blocking(pio, sm2, 3 - 1);
+	pio_sm_put_blocking(pio, sm2, 500 - 3 - 1);
+
+	printf("Start!\n");
 
 	while (true)
 	{
 		for (size_t i = 0; i < sizeof(frames[0].data);)
 		{
-			// feed sync machine
-			if (pio_sm_get_tx_fifo_level(pio, sm1) <= 4)
-			{
-				pio_sm_put_blocking(pio, sm1, 63 * 4);
-				pio_sm_put_blocking(pio, sm1, 775 * 4);
-			}
-
 			// feed pixel machine
 			if (!pio_sm_is_tx_fifo_full(pio, sm0))
 				pio_sm_put_blocking(pio, sm0, frames[0].data[i++]);
 		}
-		// printf(".");
-
-		// sleep_ms(1000);
 	}
 }

src/vga.pio

@@ -6,19 +6,49 @@ loop:
     out pins, 1 [2]
     jmp loop
 
-.program vga_sync
+.program vga_hsync
 
-entrypoint_vga_sync:
-loop:
+entrypoint_vga_hsync:
     pull
-    mov x, osr
+    mov isr, osr
+    pull
+
+loop:
+    nop
+    irq set 0
+
+    mov x, isr
     set pins, 0
 hsync_pulse:
     jmp x-- hsync_pulse
 
-    pull
     mov x, osr
     set pins, 1
 hsync_idle:
     jmp x-- hsync_idle
+    nop
+    jmp loop
+
+
+.program vga_vsync
+
+entrypoint_vga_vsync:
+    pull
+    mov isr, osr
+    pull
+
+loop:
+
+    mov x, isr
+vsync_pulse:
+    wait irq 0
+    set pins, 0
+    jmp x-- vsync_pulse
+
+    mov x, osr
+vsync_idle:
+    wait irq 0
+    set pins, 1
+    jmp x-- vsync_idle
+
     jmp loop