Add 8086 USB Interposer board (#1767)

src/boards/include/boards/net8086_usb_interposer.h

+/*
+ * Copyright (c) 2020 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_NET8086_USB_INTERPOSER_H
+#define _BOARDS_NET8086_USB_INTERPOSER_H
+
+// For board detection
+#define NET8086_USB_INTERPOSER
+
+// On some samples, the xosc can take longer to stabilize than is usual
+#ifndef PICO_XOSC_STARTUP_DELAY_MULTIPLIER
+#define PICO_XOSC_STARTUP_DELAY_MULTIPLIER 64
+#endif
+
+//------------- UART -------------//
+#ifndef PICO_DEFAULT_UART
+#define PICO_DEFAULT_UART 0
+#endif
+
+#ifndef PICO_DEFAULT_UART_TX_PIN
+#define PICO_DEFAULT_UART_TX_PIN 0
+#endif
+
+#ifndef PICO_DEFAULT_UART_RX_PIN
+#define PICO_DEFAULT_UART_RX_PIN 1
+#endif
+
+//------------- LED -------------//
+#ifndef PICO_DEFAULT_LED_PIN
+#define PICO_DEFAULT_LED_PIN 7
+#endif
+
+//------------- I2C -------------//
+#ifndef PICO_DEFAULT_I2C
+#define PICO_DEFAULT_I2C 1
+#endif
+
+#ifndef PICO_DEFAULT_I2C_SDA_PIN
+#define PICO_DEFAULT_I2C_SDA_PIN 14
+#endif
+
+#ifndef PICO_DEFAULT_I2C_SCL_PIN
+#define PICO_DEFAULT_I2C_SCL_PIN 15
+#endif
+
+//------------- FLASH -------------//
+
+// Use slower generic flash access
+#define PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H 1
+
+#ifndef PICO_FLASH_SPI_CLKDIV
+#define PICO_FLASH_SPI_CLKDIV 4
+#endif
+
+#ifndef PICO_FLASH_SIZE_BYTES
+#define PICO_FLASH_SIZE_BYTES (16 * 1024 * 1024)
+#endif
+
+// All boards have B1 RP2040
+#ifndef PICO_RP2040_B0_SUPPORTED
+#define PICO_RP2040_B0_SUPPORTED 0
+#endif
+
+#endif