Add hsync and vsync signals for 480x640 resolution

flake.nix

@@ -1,38 +1,41 @@
 {
-    inputs = {
-	nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
-	flake-utils.url = "github:numtide/flake-utils";
-    };
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
 
-    outputs =
-	{ 
-	nixpkgs,
-	flake-utils,
-	...
-	}: flake-utils.lib.eachDefaultSystem(system: 
-	    let
-		pkgs = import nixpkgs { inherit system; };
-		pico-sdk = pkgs.pico-sdk.override {
-		    withSubmodules = true;
-		};
-		PICO_SDK_PATH = "${pico-sdk}/lib/pico-sdk";
-	    in {
-		devShell = pkgs.mkShell {
-		    name = "PicoVGA dev shell";
-		    inputsFrom = [ pico-sdk ];
-		    packages = with pkgs; [
-			gcc-arm-embedded
-			python3
+  outputs =
+    { nixpkgs
+    , flake-utils
+    , ...
+    }:
+    flake-utils.lib.eachDefaultSystem (system:
+    let
+      pkgs = import nixpkgs { inherit system; };
+      pico-sdk = pkgs.pico-sdk.override {
+        withSubmodules = true;
+      };
+      PICO_SDK_PATH = "${pico-sdk}/lib/pico-sdk";
+    in
+    {
+      devShell = pkgs.mkShell {
+        name = "PicoVGA dev shell";
+        inputsFrom = [ pico-sdk ];
+        packages = with pkgs; [
+          gcc-arm-embedded
+          python3
+          pico-sdk
 
-			usbutils
-			picotool
-			pico-sdk
-		    ];
-		    shellHook = ''
-		    ln -sf ${PICO_SDK_PATH}/external/pico_sdk_import.cmake pico_sdk_import.cmake
-		    '';
+          picocom
 
-		    inherit PICO_SDK_PATH;
-		};
-	    });
+          usbutils
+          picotool
+        ];
+        shellHook = ''
+          ln -sf ${PICO_SDK_PATH}/external/pico_sdk_import.cmake pico_sdk_import.cmake
+        '';
+
+        inherit PICO_SDK_PATH;
+      };
+    });
 }

src/main.cpp

@@ -1,25 +1,42 @@
 #include "hardware/gpio.h"
 #include "pico/stdlib.h"
+#include <pico/time.h>
+
+#include <concepts>
 #include <cstdint>
 #include <cstdio>
-#include <pico/time.h>
 
 constexpr static uint start_pin = 2;
 constexpr static uint pin_mask = (0xFFF) << start_pin;
 
+template <std::integral T> constexpr bool between(T x, T min, T max) {
+  return (x >= min) && (x < max);
+}
+
 int main() {
   stdio_init_all();
 
   for (uint offset{}; offset != 14; ++offset) {
     auto const pin = start_pin + offset;
+    std::printf("Initializing GPIO %d\n", pin);
     gpio_init(pin);
     gpio_set_dir(pin, GPIO_OUT);
   }
 
-  for (uint16_t pixel{};; ++pixel) {
-    auto const set_mask = (pixel & 0xFFF) << start_pin;
-    printf("Set mask=%03x", pixel);
-    gpio_put_masked(pin_mask, set_mask);
-    sleep_ms(100);
+  for (uint32_t y{}; y != 525; ++y) {
+    for (uint32_t x{}; x != 800; ++x) {
+      const auto is_blanking = y >= 480 || x >= 640;
+      const auto hsync = between(x, 656ul, 752ul);
+      const auto vsync = between(y, 490ul, 492ul);
+
+      auto const pixel = (0u << 8) | ((y & 0xF) << 4) | (x & 0xF);
+      auto const set_mask =
+          (((uint32_t)vsync << 13) | ((uint32_t)hsync << 12) | (pixel & 0xFFF))
+          << start_pin;
+
+      std::printf("Set mask=%04X\n", set_mask >> start_pin);
+      gpio_put_masked(pin_mask, set_mask);
+      sleep_ms(10);
+    }
   }
 }