Correct Pi 500 board support: RP2040 chip, proper naming

- Rename to raspberry_pi_pi500_rp2040.h for clarity
- Correct chip type from RP2350 to RP2040
- Remove pico2.h inheritance, use self-contained definitions
- Add comprehensive GPIO pin mapping documentation
- Include critical power management warning
- Configure W25X10CL flash support for RP2040

Author: jhordiesluminus

src/boards/include/boards/raspberry_pi_pi500.h

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2024 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// -----------------------------------------------------
+// NOTE: THIS HEADER IS ALSO INCLUDED BY ASSEMBLER SO
+//       SHOULD ONLY CONSIST OF PREPROCESSOR DIRECTIVES
+// -----------------------------------------------------
+
+#ifndef _BOARDS_RASPBERRY_PI_PI500_RP2040_H
+#define _BOARDS_RASPBERRY_PI_PI500_RP2040_H
+
+pico_board_cmake_set(PICO_PLATFORM, rp2040)
+
+// For board detection
+#define RASPBERRY_PI_PI500_RP2040
+
+// --- UART ---
+#ifndef PICO_DEFAULT_UART
+#define PICO_DEFAULT_UART 0
+#endif
+#ifndef PICO_DEFAULT_UART_TX_PIN
+#define PICO_DEFAULT_UART_TX_PIN 16  // Pi 500 debug UART on GP16
+#endif
+#ifndef PICO_DEFAULT_UART_RX_PIN
+#define PICO_DEFAULT_UART_RX_PIN 1   // Standard RX pin
+#endif
+
+// --- LED ---
+#ifndef PICO_DEFAULT_LED_PIN
+#define PICO_DEFAULT_LED_PIN 17  // Pi 500 LED on GP17
+#endif
+
+// --- I2C ---
+#ifndef PICO_DEFAULT_I2C
+#define PICO_DEFAULT_I2C 0
+#endif
+#ifndef PICO_DEFAULT_I2C_SDA_PIN
+#define PICO_DEFAULT_I2C_SDA_PIN 4
+#endif
+#ifndef PICO_DEFAULT_I2C_SCL_PIN
+#define PICO_DEFAULT_I2C_SCL_PIN 5
+#endif
+
+// --- SPI ---
+#ifndef PICO_DEFAULT_SPI
+#define PICO_DEFAULT_SPI 0
+#endif
+#ifndef PICO_DEFAULT_SPI_SCK_PIN
+#define PICO_DEFAULT_SPI_SCK_PIN 18
+#endif
+#ifndef PICO_DEFAULT_SPI_TX_PIN
+#define PICO_DEFAULT_SPI_TX_PIN 19
+#endif
+#ifndef PICO_DEFAULT_SPI_RX_PIN
+#define PICO_DEFAULT_SPI_RX_PIN 16
+#endif
+#ifndef PICO_DEFAULT_SPI_CSN_PIN
+#define PICO_DEFAULT_SPI_CSN_PIN 17
+#endif
+
+// --- FLASH ---
+// Pi 500 uses W25X10CL flash (differs from standard Pico W25Q080)
+#define PICO_BOOT_STAGE2_CHOOSE_W25X10CL 1
+
+#ifndef PICO_FLASH_SPI_CLKDIV
+#define PICO_FLASH_SPI_CLKDIV 2
+#endif
+
+pico_board_cmake_set_default(PICO_FLASH_SIZE_BYTES, (1 * 1024 * 1024))  // 1MB W25X10CL
+#ifndef PICO_FLASH_SIZE_BYTES
+#define PICO_FLASH_SIZE_BYTES (1 * 1024 * 1024)
+#endif
+
+// Drive high to force power supply into PWM mode (lower ripple on 3V3 at light loads)
+#define PICO_SMPS_MODE_PIN 23
+
+#ifndef PICO_RP2040_B0_SUPPORTED
+#define PICO_RP2040_B0_SUPPORTED 1
+#endif
+
+// The GPIO Pin used to read VBUS to determine if the device is battery powered.
+#ifndef PICO_VBUS_PIN
+#define PICO_VBUS_PIN 24
+#endif
+
+// The GPIO Pin used to monitor VSYS. Typically you would use this with ADC.
+#ifndef PICO_VSYS_PIN
+#define PICO_VSYS_PIN 29
+#endif
+
+// --- USB CONFIGURATION ---
+// Crucial for Pi 500 keyboard function when Pi is off - ignores USB startup check
+#define PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE 0
+#define PICO_STDIO_USB_RESET_BOOTSEL_ACTIVITY_LED 0
+
+// --- BOOTLOADER CONFIGURATION ---
+// Disable double tap reset timeout for Pi 500
+#define PICO_BOOTSEL_VIA_DOUBLE_RESET_ACTIVITY_LED 0
+
+// --- PI 500 KEYBOARD MATRIX CONFIGURATION ---
+// Complete GPIO pin mapping for 8×18 keyboard matrix
+// Rows (8): GP0, GP1, GP2, GP3, GP4, GP5, GP6, GP7
+// Cols (18): GP27, GP8, GP9, GP10, GP11, GP12, GP13, GP14, GP23, GP24, GP22, GP20, GP29, GP18, GP15, GP21, GP28, GP26
+// Matrix scanning: ROW2COL, no diodes (ghost keys possible with 3+ key combinations)
+
+// --- PI 500 SYSTEM PINS ---
+// These pins are reserved for Pi 500 hardware functions:
+// GP0-GP7: Keyboard matrix rows
+// GP8-GP15: Keyboard matrix columns (partial)
+// GP16: Debug UART TX
+// GP17: LED (heartbeat/debug)
+// GP18: Keyboard matrix column
+// GP19: Power button control (PWR_BTN) - CRITICAL for Pi power management
+// GP20: Power key detection column (separate from matrix)
+// GP21-GP24: Keyboard matrix columns
+// GP25: Caps Lock LED
+// GP26-GP29: Keyboard matrix columns
+
+// --- POWER MANAGEMENT WARNING ---
+// Custom firmware MUST implement power button handling via GP19 or the Pi 500
+// power button will stop working, potentially making the device unbootable.
+// See QMK pi500.c for reference implementation.
+
+#endif