example: add MIDI 2.0 Host example with display (midi2_host)

Add Host example that receives UMP from a MIDI 2.0 Device via PIO-USB
and displays received messages on a SSD1306 OLED (I2C, 128x64).

Features:
- Boot checklist on display (PWR, TinyUSB, USB bus, Device, Descriptor,
  Alt Setting UMP, Mount, Receiving)
- Decode and display all MIDI 2.0 Channel Voice messages
- PIO-USB Host on rhport 1 (GP12/GP13 for Waveshare RP2350-USB-A)
- SSD1306 display via I2C0 (GP4=SDA, GP5=SCL)

Also add board definition for Waveshare RP2350-USB-A.

Tested: Waveshare RP2350-USB-A (Host) receiving UMP from Raspberry Pi
Pico (Device) via USB cable, notes displayed on SSD1306 OLED

1 files changed, 220 insertions, 0 deletions

diff --git a/examples/host/midi2_host/src/display.c b/examples/host/midi2_host/src/display.c
new file mode 100644
index 000000000..6d81bcd5c
--- /dev/null
+++ b/examples/host/midi2_host/src/display.c
@@ -0,0 +1,220 @@
+/*
+ * 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.
+// Minimal text-only implementation, no graphics library.
+// I2C0: SDA = GP4, SCL = GP5, Address = 0x3C
+
+#include "display.h"
+#include <stdio.h>
+#include <string.h>
+#include "pico/stdlib.h"
+#include "hardware/i2c.h"
+#include "hardware/gpio.h"
+
+#define I2C_PORT     i2c0
+#define I2C_SDA      4
+#define I2C_SCL      5
+#define I2C_FREQ     400000
+#define SSD1306_ADDR 0x3C
+
+#define SCR_W        128
+#define SCR_H        64
+#define PAGES        (SCR_H / 8)   // 8 pages
+#define CHARS_PER_LINE 21          // 128 / 6 = 21 chars
+
+// Framebuffer
+static uint8_t fb[SCR_W * PAGES];
+
+// Log buffer
+#define LOG_LINES    3
+static char log_lines[LOG_LINES][CHARS_PER_LINE + 1];
+static int log_count = 0;
+
+// Status line
+static char status_text[CHARS_PER_LINE + 1] = "";
+
+//--------------------------------------------------------------------+
+// Minimal 5x7 font (ASCII 32-126)
+//--------------------------------------------------------------------+
+#include "font5x7.h"
+
+//--------------------------------------------------------------------+
+// SSD1306 I2C commands
+//--------------------------------------------------------------------+
+
+static void ssd_cmd(uint8_t cmd) {
+  uint8_t buf[2] = { 0x00, cmd };  // Co=0, D/C=0
+  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;  // Co=0, D/C=1
+  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);  // Column range
+  ssd_cmd(0x22); ssd_cmd(0); ssd_cmd(7);    // Page range
+  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++;
+  }
+}
+
+//--------------------------------------------------------------------+
+// Display API
+//--------------------------------------------------------------------+
+
+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);        // Display off
+  ssd_cmd(0xD5); ssd_cmd(0x80);  // Clock div
+  ssd_cmd(0xA8); ssd_cmd(0x3F);  // Multiplex 64
+  ssd_cmd(0xD3); ssd_cmd(0x00);  // Display offset
+  ssd_cmd(0x40);        // Start line 0
+  ssd_cmd(0x8D); ssd_cmd(0x14);  // Charge pump on
+  ssd_cmd(0x20); ssd_cmd(0x00);  // Horizontal addressing
+  ssd_cmd(0xA1);        // Segment remap
+  ssd_cmd(0xC8);        // COM scan direction
+  ssd_cmd(0xDA); ssd_cmd(0x12);  // COM pins
+  ssd_cmd(0x81); ssd_cmd(0xCF);  // Contrast
+  ssd_cmd(0xD9); ssd_cmd(0xF1);  // Pre-charge
+  ssd_cmd(0xDB); ssd_cmd(0x40);  // VCOMH deselect
+  ssd_cmd(0xA4);        // Display from RAM
+  ssd_cmd(0xA6);        // Normal display
+  ssd_cmd(0xAF);        // Display on
+
+  fb_clear();
+  fb_string(0, 0, "MIDI 2.0 Host");
+  ssd_flush();
+}
+
+void display_checklist_update(const checklist_t* ck) {
+  struct { const char* label; bool ok; } items[] = {
+    { "PWR",       ck->pwr_on },
+    { "TinyUSB",   ck->tusb_init },
+    { "USB bus",   ck->bus_active },
+    { "Device",    ck->device_connected },
+    { "Descript",  ck->descriptor_parsed },
+    { "Alt1 UMP",  ck->alt_setting_ok },
+    { "Mount",     ck->mounted },
+    { "RX UMP",    ck->receiving },
+  };
+
+  // Clear checklist area (lines 1-4, two columns)
+  for (int p = 1; p <= 4; p++) {
+    memset(&fb[p * SCR_W], 0, SCR_W);
+  }
+
+  for (int i = 0; i < 8; i++) {
+    int col = (i < 4) ? 0 : 64;
+    int row = (i < 4) ? i : i - 4;
+    int y = 9 + row * 8;
+    char line[12];
+    snprintf(line, sizeof(line), "%s %s", items[i].ok ? "OK" : "..", items[i].label);
+    fb_string(col, y, line);
+  }
+
+  ssd_flush();
+}
+
+void display_log(const char* text, uint16_t color) {
+  (void)color;  // SSD1306 is monochrome
+
+  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_count = LOG_LINES - 1;
+  }
+
+  strncpy(log_lines[log_count], text, CHARS_PER_LINE);
+  log_lines[log_count][CHARS_PER_LINE] = '\0';
+  log_count++;
+
+  // Draw log area (pages 5-6, y=40-55)
+  memset(&fb[5 * SCR_W], 0, SCR_W);
+  memset(&fb[6 * SCR_W], 0, SCR_W);
+
+  for (int i = 0; i < log_count && i < LOG_LINES; i++) {
+    fb_string(0, 41 + i * 8, log_lines[i]);
+  }
+
+  ssd_flush();
+}
+
+void display_status(const char* text) {
+  strncpy(status_text, text, CHARS_PER_LINE);
+  status_text[CHARS_PER_LINE] = '\0';
+
+  // Status on last page (y=56)
+  memset(&fb[7 * SCR_W], 0, SCR_W);
+  fb_string(0, 56, status_text);
+  ssd_flush();
+}