Add USB Serial GameCube Controller Example for Pico SDK

examples/pico-sdk/gcn-controller-target/usb_serial/.gitignore

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+build/

examples/pico-sdk/gcn-controller-target/usb_serial/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20)
+
+set(JOYBUS_BACKEND_RP2XXX TRUE)
+set(LIBJOYBUS_ROOT ${CMAKE_CURRENT_LIST_DIR}/../../../..)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+if(WIN32)
+    set(USERHOME $ENV{USERPROFILE})
+else()
+    set(USERHOME $ENV{HOME})
+endif()
+set(sdkVersion 2.2.0)
+set(toolchainVersion 14_2_Rel1)
+set(picotoolVersion 2.2.0-a4)
+set(picoVscode ${USERHOME}/.pico-sdk/cmake/pico-vscode.cmake)
+if (EXISTS ${picoVscode})
+    include(${picoVscode})
+endif()
+include($ENV{PICO_SDK_PATH}/external/pico_sdk_import.cmake)
+
+set(PICO_BOARD pico2 CACHE STRING "Board type")
+
+project(usb_serial C CXX ASM)
+
+# Initialise the Raspberry Pi Pico SDK
+pico_sdk_init()
+
+add_subdirectory(${LIBJOYBUS_ROOT} ${CMAKE_BINARY_DIR}/_deps/libjoybus-build)
+
+# Add executable. Default name is the project name, version 0.1
+
+add_executable(usb_serial main.c)
+
+pico_enable_stdio_usb(usb_serial 1)
+pico_enable_stdio_uart(usb_serial 0)
+
+target_link_libraries(usb_serial pico_stdlib)
+pico_add_extra_outputs(usb_serial)
+
+# pull in common dependencies
+target_link_libraries(usb_serial pico_stdlib joybus)
+
+# create map/bin/hex/uf2 file etc.
+pico_add_extra_outputs(usb_serial)
+
+# add url via pico_set_program_url

examples/pico-sdk/gcn-controller-target/usb_serial/README.txt

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+# Pico SDK GameCube Controller Target USB Serial Example
+
+Act as a GameCube controller on RP2XXX devices using the Pico SDK using a serial interface. Simulates button presses when an input is sent over a usb serial connection.
+
+## Building
+
+```bash
+cmake -B build -DPICO_ENABLE_STDIO_USB=1 -DPICO_ENABLE_STDIO_UART=0 -DPICO_BOARD=pico2 -DPICO_PLATFORM=rp2350 . && cmake --build build
+```  
+or  
+```bash
+cmake -B build -DPICO_ENABLE_STDIO_USB=1 -DPICO_ENABLE_STDIO_UART=0 . && cmake --build build
+```  
+
+## Flashing
+
+Enter bootloader mode by holding the BOOTSEL button while plugging in the Pico. Then copy the generated `build/usb_serial.uf2` file to the RPI-RP2 drive that appears, or use `picotool`:
+
+```bash
+picotool load -f build/usb_serial.uf2
+```

examples/pico-sdk/gcn-controller-target/usb_serial/main.c

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+#include <stdio.h>
+#include "pico/stdlib.h"
+
+#include <joybus/joybus.h>
+#include <joybus/backend/rp2xxx.h>
+
+#define SI_DATA_GPIO  12
+
+struct joybus_rp2xxx rp2xxx_bus;
+struct joybus *bus = JOYBUS(&rp2xxx_bus);
+
+static struct joybus_gc_controller gc_controller;
+
+int main()
+{
+  stdio_init_all(); // USB serial
+  sleep_ms(2000);   // allow time to connect
+
+  // Initialize Joybus
+  joybus_rp2xxx_init(&rp2xxx_bus, SI_DATA_GPIO, pio0);
+  joybus_enable(bus);
+
+  // Initialize controller target
+  joybus_gc_controller_init(&gc_controller, JOYBUS_GAMECUBE_CONTROLLER);
+
+  // Register the target on the bus
+  joybus_target_register(bus, JOYBUS_TARGET(&gc_controller));
+
+  while (1) {
+    // Clear previous button state
+    gc_controller.input.buttons &= ~JOYBUS_GCN_BUTTON_MASK;
+
+    // Read USB serial input (non-blocking)
+    int ch = getchar_timeout_us(0);
+
+    if (ch != PICO_ERROR_TIMEOUT) {
+      if (ch == 'a')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_A;
+      if (ch == 'b')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_B;
+      if (ch == 'x')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_X;
+      if (ch == 'y')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_Y;
+      if (ch == 's')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_START;
+      if (ch == 'z')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_Z;
+      if (ch == 'l')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_L;
+      if (ch == 'r')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_R;
+      if (ch == 'u')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_UP;
+      if (ch == 'd')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_DOWN;
+      if (ch == 'L')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_LEFT;
+      if (ch == 'R')
+        gc_controller.input.buttons |= JOYBUS_GCN_BUTTON_RIGHT;
+    }
+
+    sleep_ms(10);
+  }
+
+  return 0;
+}