example: add MIDI 2.0 Host example for Adafruit Feather RP2040 USB Host

Board-specific variant of midi2_host targeting the Adafruit Feather
RP2040 with USB Type A Host (product 5723).

Hardware differences from the Waveshare RP2350-USB-A example:
- PIO-USB on GP16/GP17 (vs GP12/GP13)
- I2C1 via STEMMA QT on GP2/GP3 (vs I2C0 GP4/GP5)
- USB Host 5V power enable on GP18

Display uses three phases: splash screen, spinner while waiting for
a device, then live scrolling UMP message view with 6 visible lines.

Tested board-to-board: RP2040 Pico (Device) to Feather RP2040 (Host),
SSD1306 128x64 OLED showing decoded MIDI 2.0 messages in real time.

Author: sauloverissimo

examples/host/midi2_host_feather/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20)
+
+include(${CMAKE_CURRENT_SOURCE_DIR}/../../../hw/bsp/family_support.cmake)
+
+project(midi2_host_feather C CXX ASM)
+
+family_initialize_project(${PROJECT_NAME} ${CMAKE_CURRENT_LIST_DIR})
+
+# This example requires PIO-USB and Pico SDK (I2C, SSD1306 display)
+if(NOT FAMILY STREQUAL "rp2040")
+  return()
+endif()
+
+add_executable(${PROJECT_NAME})
+
+target_sources(${PROJECT_NAME} PUBLIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/main.c
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/display.c
+)
+
+target_include_directories(${PROJECT_NAME} PUBLIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/src
+)
+
+family_configure_host_example(${PROJECT_NAME} noos)
+
+# Adafruit Feather RP2040 USB Host: PIO-USB on GP16/GP17
+target_compile_definitions(${PROJECT_NAME} PRIVATE
+  PIO_USB_DP_PIN_DEFAULT=16
+)
+target_compile_options(${PROJECT_NAME} PRIVATE
+  -Wno-type-limits
+)
+
+# SSD1306 display (I2C via STEMMA QT)
+target_link_libraries(${PROJECT_NAME} PUBLIC
+  hardware_i2c
+)

examples/host/midi2_host_feather/Makefile

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+include ../../../examples/build_system/make/make.mk

examples/host/midi2_host_feather/src/display.c

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2026 Saulo Verissimo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+// SSD1306 OLED display driver (128x64, I2C) for MIDI 2.0 Host example.
+// Adafruit Feather RP2040 USB Host: I2C1 via STEMMA QT (SDA = GP2, SCL = GP3)
+//
+// Three display phases:
+//   1. Splash     : title + credits (shown during init)
+//   2. Connecting : spinner animation while waiting for device
+//   3. Live       : header + 6 scrolling log lines + status bar
+
+#include "display.h"
+#include <stdio.h>
+#include <string.h>
+#include "pico/stdlib.h"
+#include "hardware/i2c.h"
+#include "hardware/gpio.h"
+
+#define I2C_PORT     i2c1
+#define I2C_SDA      2
+#define I2C_SCL      3
+#define I2C_FREQ     400000
+#define SSD1306_ADDR 0x3C
+
+#define SCR_W        128
+#define SCR_H        64
+#define PAGES        (SCR_H / 8)
+#define CHARS_PER_LINE 21
+
+//--------------------------------------------------------------------+
+// Framebuffer
+//--------------------------------------------------------------------+
+
+static uint8_t fb[SCR_W * PAGES];
+
+//--------------------------------------------------------------------+
+// Log buffer (6 lines for live view)
+//--------------------------------------------------------------------+
+
+#define LOG_LINES    6
+static char log_lines[LOG_LINES][CHARS_PER_LINE + 1];
+static int log_count = 0;
+
+//--------------------------------------------------------------------+
+// Minimal 5x7 font (ASCII 32-126)
+//--------------------------------------------------------------------+
+
+#include "font5x7.h"
+
+//--------------------------------------------------------------------+
+// SSD1306 I2C low-level
+//--------------------------------------------------------------------+
+
+static void ssd_cmd(uint8_t cmd) {
+  uint8_t buf[2] = { 0x00, cmd };
+  i2c_write_blocking(I2C_PORT, SSD1306_ADDR, buf, 2, false);
+}
+
+static void ssd_data(const uint8_t* data, size_t len) {
+  uint8_t buf[SCR_W + 1];
+  buf[0] = 0x40;
+  size_t chunk = (len > SCR_W) ? SCR_W : len;
+  memcpy(buf + 1, data, chunk);
+  i2c_write_blocking(I2C_PORT, SSD1306_ADDR, buf, chunk + 1, false);
+}
+
+static void ssd_flush(void) {
+  ssd_cmd(0x21); ssd_cmd(0); ssd_cmd(127);
+  ssd_cmd(0x22); ssd_cmd(0); ssd_cmd(7);
+  for (int page = 0; page < PAGES; page++) {
+    ssd_data(&fb[page * SCR_W], SCR_W);
+  }
+}
+
+//--------------------------------------------------------------------+
+// Framebuffer drawing
+//--------------------------------------------------------------------+
+
+static void fb_clear(void) {
+  memset(fb, 0, sizeof(fb));
+}
+
+static void fb_char(int x, int y, char c) {
+  if (c < 32 || c > 126) c = '?';
+  const uint8_t* glyph = font5x7 + (c - 32) * 5;
+  int page = y / 8;
+  int bit_offset = y % 8;
+
+  if (page >= PAGES || x + 5 > SCR_W) return;
+
+  for (int col = 0; col < 5; col++) {
+    uint8_t column_data = glyph[col];
+    fb[(page * SCR_W) + x + col] |= (uint8_t)(column_data << bit_offset);
+    if (bit_offset > 0 && page + 1 < PAGES) {
+      fb[((page + 1) * SCR_W) + x + col] |= (uint8_t)(column_data >> (8 - bit_offset));
+    }
+  }
+}
+
+static void fb_string(int x, int y, const char* str) {
+  while (*str) {
+    fb_char(x, y, *str);
+    x += 6;
+    if (x + 6 > SCR_W) break;
+    str++;
+  }
+}
+
+// Draw a horizontal line (1px)
+static void fb_hline(int x0, int x1, int y) {
+  int page = y / 8;
+  uint8_t mask = (uint8_t)(1 << (y % 8));
+  if (page >= PAGES) return;
+  for (int x = x0; x <= x1 && x < SCR_W; x++) {
+    fb[page * SCR_W + x] |= mask;
+  }
+}
+
+//--------------------------------------------------------------------+
+// Phase 1: Splash
+//--------------------------------------------------------------------+
+
+void display_init(void) {
+  i2c_init(I2C_PORT, I2C_FREQ);
+  gpio_set_function(I2C_SDA, GPIO_FUNC_I2C);
+  gpio_set_function(I2C_SCL, GPIO_FUNC_I2C);
+  gpio_pull_up(I2C_SDA);
+  gpio_pull_up(I2C_SCL);
+
+  sleep_ms(100);
+
+  // SSD1306 init sequence
+  ssd_cmd(0xAE);
+  ssd_cmd(0xD5); ssd_cmd(0x80);
+  ssd_cmd(0xA8); ssd_cmd(0x3F);
+  ssd_cmd(0xD3); ssd_cmd(0x00);
+  ssd_cmd(0x40);
+  ssd_cmd(0x8D); ssd_cmd(0x14);
+  ssd_cmd(0x20); ssd_cmd(0x00);
+  ssd_cmd(0xA1);
+  ssd_cmd(0xC8);
+  ssd_cmd(0xDA); ssd_cmd(0x12);
+  ssd_cmd(0x81); ssd_cmd(0xCF);
+  ssd_cmd(0xD9); ssd_cmd(0xF1);
+  ssd_cmd(0xDB); ssd_cmd(0x40);
+  ssd_cmd(0xA4);
+  ssd_cmd(0xA6);
+  ssd_cmd(0xAF);
+
+  // Splash screen
+  fb_clear();
+  fb_string(4,  8, "TinyUSB MIDI 2.0");
+  fb_hline(4, 123, 18);
+  fb_string(16, 24, "USB Host Demo");
+  fb_string(4, 40, "Feather RP2040");
+  fb_string(4, 52, "PIO-USB + SSD1306");
+  ssd_flush();
+}
+
+//--------------------------------------------------------------------+
+// Phase 2: Connecting (spinner)
+//--------------------------------------------------------------------+
+
+static const char SPINNER[] = "|/-\\";
+
+void display_connecting(uint32_t elapsed_ms) {
+  int idx = (int)((elapsed_ms / 200) % 4);
+
+  // Clear bottom 2 pages for spinner area
+  memset(&fb[6 * SCR_W], 0, SCR_W);
+  memset(&fb[7 * SCR_W], 0, SCR_W);
+
+  char line[CHARS_PER_LINE + 1];
+  snprintf(line, sizeof(line), "%c Waiting device...", SPINNER[idx]);
+  fb_string(4, 52, line);
+  ssd_flush();
+}
+
+//--------------------------------------------------------------------+
+// Phase 3: Live view
+//--------------------------------------------------------------------+
+
+// Layout:
+//   y=0  : "TinyUSB MIDI 2.0 Host" (header, fixed)
+//   y=9  : separator line
+//   y=10 : log line 0
+//   y=18 : log line 1
+//   y=26 : log line 2
+//   y=34 : log line 3
+//   y=42 : log line 4
+//   y=50 : log line 5
+//   y=57 : separator line
+//   y=58 : status bar
+
+static bool live_mode = false;
+
+static void draw_live_frame(void) {
+  fb_clear();
+  fb_string(0, 0, "TinyUSB MIDI 2.0 Host");
+  fb_hline(0, 127, 9);
+  fb_hline(0, 127, 57);
+}
+
+void display_live_begin(void) {
+  live_mode = true;
+  log_count = 0;
+  memset(log_lines, 0, sizeof(log_lines));
+
+  draw_live_frame();
+  fb_string(0, 58, "Connected");
+  ssd_flush();
+}
+
+void display_log(const char* text, uint16_t color) {
+  (void)color;
+
+  if (!live_mode) {
+    display_live_begin();
+  }
+
+  // Scroll up if full
+  if (log_count >= LOG_LINES) {
+    for (int i = 0; i < LOG_LINES - 1; i++) {
+      strncpy(log_lines[i], log_lines[i + 1], CHARS_PER_LINE);
+      log_lines[i][CHARS_PER_LINE] = '\0';
+    }
+    log_count = LOG_LINES - 1;
+  }
+
+  strncpy(log_lines[log_count], text, CHARS_PER_LINE);
+  log_lines[log_count][CHARS_PER_LINE] = '\0';
+  log_count++;
+
+  // Redraw: header + log + status
+  draw_live_frame();
+  for (int i = 0; i < log_count && i < LOG_LINES; i++) {
+    fb_string(0, 10 + i * 8, log_lines[i]);
+  }
+  ssd_flush();
+}
+
+void display_status(const char* text) {
+  if (!live_mode) return;
+
+  // Clear status area (page 7)
+  memset(&fb[7 * SCR_W], 0, SCR_W);
+  // Redraw separator (might have been cleared)
+  fb_hline(0, 127, 57);
+
+  char status[CHARS_PER_LINE + 1];
+  strncpy(status, text, CHARS_PER_LINE);
+  status[CHARS_PER_LINE] = '\0';
+  fb_string(0, 58, status);
+  ssd_flush();
+}

examples/host/midi2_host_feather/src/display.h

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2026 Saulo Verissimo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef DISPLAY_H_
+#define DISPLAY_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+
+// Initialize SSD1306 display and show splash screen
+void display_init(void);
+
+// Show waiting/connecting animation (call periodically)
+void display_connecting(uint32_t elapsed_ms);
+
+// Transition to live message view
+void display_live_begin(void);
+
+// Add a line to the scrolling log area (6 visible lines)
+void display_log(const char* text, uint16_t color);
+
+// Update the status bar (bottom line)
+void display_status(const char* text);
+
+#endif