stmhal/boards/STM32L476DISC: Use external SPI flash for filesystem.

stmhal/boards/STM32L476DISC/board_init.c

+#include "py/mphal.h"
+#include "genhdr/pins.h"
+
+void STM32L476DISC_board_early_init(void) {
+    // set SPI flash WP and HOLD pins high
+    mp_hal_pin_output(&pin_E14);
+    mp_hal_pin_output(&pin_E15);
+    mp_hal_pin_write(&pin_E14, 1);
+    mp_hal_pin_write(&pin_E15, 1);
+}

stmhal/boards/STM32L476DISC/mpconfigboard.h

 #include STM32_HAL_H
 
+#define MICROPY_BOARD_EARLY_INIT    STM32L476DISC_board_early_init
+void STM32L476DISC_board_early_init(void);
+
 #define MICROPY_HW_BOARD_NAME       "L476-DISCO"
 #define MICROPY_HW_MCU_NAME         "STM32L476"
 
@@ -16,6 +19,13 @@
 #define MICROPY_HW_ENABLE_DAC       (0)
 #define MICROPY_HW_ENABLE_CAN       (0)
 
+// use external SPI flash for storage
+#define MICROPY_HW_SPIFLASH_SIZE_BITS (128 * 1024 * 1024)
+#define MICROPY_HW_SPIFLASH_CS      (pin_E11)
+#define MICROPY_HW_SPIFLASH_SCK     (pin_E10)
+#define MICROPY_HW_SPIFLASH_MOSI    (pin_E12)
+#define MICROPY_HW_SPIFLASH_MISO    (pin_E13)
+
 // MSI is used and is 4MHz
 #define MICROPY_HW_CLK_PLLM (1)
 #define MICROPY_HW_CLK_PLLN (40)