circuitpython/atmel-samd/boards/circuitplayground_express/mpconfigboard.h

#define USB_REPL

#define MICROPY_HW_BOARD_NAME "Adafruit CircuitPlayground Express"
#define MICROPY_HW_MCU_NAME "samd21g18"

//#define MICROPY_HW_LED_MSC  PIN_PA17

#define SPI_FLASH_BAUDRATE  (1000000)

// On-board flash
#define SPI_FLASH_MUX_SETTING SPI_SIGNAL_MUX_SETTING_E
// Use default pinmux for the chip select since we manage it ourselves.

// Rev B:
// #define SPI_FLASH_PAD0_PINMUX PINMUX_PA12D_SERCOM4_PAD0 // MISO
// #define SPI_FLASH_PAD1_PINMUX PINMUX_DEFAULT // CS
// #define SPI_FLASH_PAD2_PINMUX PINMUX_PB10D_SERCOM4_PAD2 // MOSI
// #define SPI_FLASH_PAD3_PINMUX PINMUX_PB11D_SERCOM4_PAD3 // SCK

// Rev C:
#define SPI_FLASH_PAD0_PINMUX PINMUX_PA16D_SERCOM3_PAD0 // MISO
#define SPI_FLASH_PAD1_PINMUX PINMUX_DEFAULT // CS
#define SPI_FLASH_PAD2_PINMUX PINMUX_PA20D_SERCOM3_PAD2 // MOSI
#define SPI_FLASH_PAD3_PINMUX PINMUX_PA21D_SERCOM3_PAD3 // SCK

#define SPI_FLASH_CS          PIN_PB22
// rev B: #define SPI_FLASH_SERCOM      SERCOM4
#define SPI_FLASH_SERCOM      SERCOM3

// PA24 and PA25 are USB.
#define MICROPY_PORT_A        (PORT_PA16 | PORT_PA20 | PORT_PA21 | PORT_PA24 | PORT_PA25)
#define MICROPY_PORT_B        (PORT_PB22)

#define AUTORESET_DELAY_MS 500

#include "spi_flash.h"

#define BOARD_FLASH_SIZE (0x00040000 - 0x2000)

#define CALIBRATE_CRYSTALLESS 1