samd: Add support for VfsRom filesystem for SAMD21 and SAMD51.

The flash driver is update to support the new `mp_vfs_rom_ioctl()` function, and the buffer protocol is added to `samd_flash_type` (it is needed for VfsRom on devices without external flash). For SAMD21, only boards with external SPI flash have VfsRom enabled, due to size constraints. For such boards, the VfsRom filesystem has a size of 12k and is placed at the upper end of the flash. The `onewire`, `ds18x20` and `dht` drivers have been removed from frozen bytecode as they can be placed into the VfsRom files when needed. For SAMD51, the VfsRom filesystem has a default size of 64k for SAMD51x19 and 256K for SAMD51x20. It is placed at the upper end of the flash. For boards with external SPI flash, the code size is reduced from 496K to 432K. If that is not sufficient for some boards or configurations, it can be changed for each board or board variant. Tested with ADAFRUIT_ITSYBITSY_M0_EXPRESS, ADAFRUIT_ITSYBITSY_M4_EXPRESS, SPARKFUN_SAMD51_THING_PLUS, SEEED_XIAO_SAMD21, SAMD_GENERIC_D51X19, and SAMD_GENERIC_D51X20. Signed-off-by: Damien George <damien@micropython.org> Signed-off-by: robert-hh <robert@hammelrath.com>
2026-01-11 06:27:14 +01:00 · 2024-11-19 08:48:29 +01:00
parent b857a9131e
commit c07b178dbd
26 changed files with 197 additions and 62 deletions
--- a/ports/samd/Makefile
+++ b/ports/samd/Makefile
@@ -90,7 +90,7 @@ CFLAGS += $(CFLAGS_EXTRA)
 CFLAGS += -DMICROPY_HW_CODESIZE=$(strip $(subst K,' ', $(MICROPY_HW_CODESIZE)))

 LDFLAGS += -nostdlib $(addprefix -T,$(LD_FILES)) -Map=$@.map --cref
-LDFLAGS += --defsym=_codesize=$(MICROPY_HW_CODESIZE)
+LDFLAGS += --defsym=_codesize=$(MICROPY_HW_CODESIZE) --defsym=_micropy_hw_romfs_part0_size=$(MICROPY_HW_ROMFS_BYTES)

 LIBS += $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)

@@ -103,6 +103,10 @@ CFLAGS += -Os -DNDEBUG
 LDFLAGS += --gc-sections --print-memory-usage
 CFLAGS += -fdata-sections -ffunction-sections
 endif
+# Disable VFSROM support if the size was set to 0
+ifeq ($(MICROPY_HW_ROMFS_BYTES),0)
+	CFLAGS += -DMICROPY_VFS_ROM=0
+endif

 # Flags for optional C++ source code
 CXXFLAGS += $(filter-out -std=c99,$(CFLAGS))
--- a/ports/samd/boards/ADAFRUIT_FEATHER_M0_EXPRESS/mpconfigboard.mk
+++ b/ports/samd/boards/ADAFRUIT_FEATHER_M0_EXPRESS/mpconfigboard.mk
@@ -5,4 +5,4 @@ TEXT0 = 0x2000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 248K
+MICROPY_HW_CODESIZE ?= 236K
--- a/ports/samd/boards/ADAFRUIT_FEATHER_M4_EXPRESS/mpconfigboard.mk
+++ b/ports/samd/boards/ADAFRUIT_FEATHER_M4_EXPRESS/mpconfigboard.mk
@@ -5,4 +5,7 @@ TEXT0 = 0x4000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 496K
+# The size of a MCU flash filesystem will be
+# 1008k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
+MICROPY_HW_CODESIZE ?= 432K
--- a/ports/samd/boards/ADAFRUIT_ITSYBITSY_M0_EXPRESS/mpconfigboard.mk
+++ b/ports/samd/boards/ADAFRUIT_ITSYBITSY_M0_EXPRESS/mpconfigboard.mk
@@ -5,4 +5,4 @@ TEXT0 = 0x2000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 248K
+MICROPY_HW_CODESIZE ?= 236K
--- a/ports/samd/boards/ADAFRUIT_ITSYBITSY_M4_EXPRESS/mpconfigboard.mk
+++ b/ports/samd/boards/ADAFRUIT_ITSYBITSY_M4_EXPRESS/mpconfigboard.mk
@@ -5,4 +5,7 @@ TEXT0 = 0x4000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 496K
+# The size of a MCU flash filesystem will be
+# 1008k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
+MICROPY_HW_CODESIZE ?= 432K
--- a/ports/samd/boards/ADAFRUIT_METRO_M4_EXPRESS/mpconfigboard.mk
+++ b/ports/samd/boards/ADAFRUIT_METRO_M4_EXPRESS/mpconfigboard.mk
@@ -7,4 +7,7 @@ TEXT0 = 0x4000
 MICROPY_PY_NETWORK ?= 1
 MICROPY_PY_NETWORK_NINAW10 ?= 1

-MICROPY_HW_CODESIZE ?= 496K
+# The size of a MCU flash filesystem will be
+# 1008k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
+MICROPY_HW_CODESIZE ?= 432K
--- a/ports/samd/boards/ADAFRUIT_QTPY_SAMD21/mpconfigvariant_SPIFLASH.mk
+++ b/ports/samd/boards/ADAFRUIT_QTPY_SAMD21/mpconfigvariant_SPIFLASH.mk
@@ -1,2 +1,2 @@
 CFLAGS += -DMICROPY_HW_SPIFLASH=1
-MICROPY_HW_CODESIZE ?= 232K
+MICROPY_HW_CODESIZE ?= 236K
--- a/ports/samd/boards/MINISAM_M4/mpconfigboard.mk
+++ b/ports/samd/boards/MINISAM_M4/mpconfigboard.mk
@@ -6,4 +6,7 @@ TEXT0 = 0x4000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 496K
+# The size of a MCU flash filesystem will be
+# 1008k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
+MICROPY_HW_CODESIZE ?= 432K
--- a/ports/samd/boards/SAMD21_XPLAINED_PRO/mpconfigboard.mk
+++ b/ports/samd/boards/SAMD21_XPLAINED_PRO/mpconfigboard.mk
@@ -3,4 +3,4 @@ CMSIS_MCU = SAMD21J18A
 LD_FILES = boards/samd21x18a.ld sections.ld
 TEXT0 = 0x2000

-MICROPY_HW_CODESIZE ?= 248K
+MICROPY_HW_CODESIZE ?= 236K
--- a/ports/samd/boards/SAMD_GENERIC_D51X19/mpconfigboard.mk
+++ b/ports/samd/boards/SAMD_GENERIC_D51X19/mpconfigboard.mk
@@ -6,6 +6,6 @@ TEXT0 = 0x4000
 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
 # The size of a MCU flash filesystem will be
-# 496k - MICROPY_HW_CODESIZE - MICROPY_HW_VFSROMSIZE
-# The default for MICROPY_HW_VFSROMSIZE is 64K
+# 496k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
 MICROPY_HW_CODESIZE ?= 368K
--- a/ports/samd/boards/SAMD_GENERIC_D51X20/mpconfigboard.mk
+++ b/ports/samd/boards/SAMD_GENERIC_D51X20/mpconfigboard.mk
@@ -7,5 +7,6 @@ TEXT0 = 0x4000
 # MicroPython settings
 # The size of a MCU flash filesystem will be
 # 1008k - MICROPY_HW_CODESIZE
-# The default for MICROPY_HW_VFSROMSIZE is 64K
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
 MICROPY_HW_CODESIZE ?= 752K
+MICROPY_HW_ROMFS_BYTES ?= 256K
--- a/ports/samd/boards/SEEED_WIO_TERMINAL/mpconfigboard.mk
+++ b/ports/samd/boards/SEEED_WIO_TERMINAL/mpconfigboard.mk
@@ -5,4 +5,7 @@ TEXT0 = 0x4000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 496K
+# The size of a MCU flash filesystem will be
+# 1008k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+# The default for MICROPY_HW_ROMFS_BYTES is 64K
+MICROPY_HW_CODESIZE ?= 432K
--- a/ports/samd/boards/SPARKFUN_REDBOARD_TURBO/mpconfigboard.mk
+++ b/ports/samd/boards/SPARKFUN_REDBOARD_TURBO/mpconfigboard.mk
@@ -5,4 +5,4 @@ TEXT0 = 0x2000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 232K
+MICROPY_HW_CODESIZE ?= 236K
--- a/ports/samd/boards/SPARKFUN_SAMD51_THING_PLUS/mpconfigboard.mk
+++ b/ports/samd/boards/SPARKFUN_SAMD51_THING_PLUS/mpconfigboard.mk
@@ -5,4 +5,7 @@ TEXT0 = 0x4000

 # The ?='s allow overriding in mpconfigboard.mk.
 # MicroPython settings
-MICROPY_HW_CODESIZE ?= 1008K
+# The size of a MCU flash filesystem will be
+# 1008k - MICROPY_HW_CODESIZE - MICROPY_HW_ROMFS_BYTES
+MICROPY_HW_CODESIZE ?= 752K
+MICROPY_HW_ROMFS_BYTES ?= 256K
--- a/ports/samd/boards/samd21x18a.ld
+++ b/ports/samd/boards/samd21x18a.ld
@@ -3,8 +3,8 @@
 */

 /*
-_codesize is defined in mpconfigmcu.mk or mpconfigboard.mk as
-MICROPY_HW_CODESIZE and is set in Makefile
+_codesize and _micropy_hw_romfs_part0_size are defined in mpconfigmcu.mk or mpconfigboard.mk
+as MICROPY_HW_CODESIZE and MICROPY_HW_ROMFS_BYTES and are set in Makefile.
 */

 _flashsize = 256K;  /* The physical flash size */
@@ -21,8 +21,17 @@ MEMORY
 _estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
 _sstack = _estack - 8K;

-_oflash_fs = ORIGIN(FLASH) + _codesize;
-_sflash_fs = _flashsize - _codesize - _bootloader;
+/*
+The VfsROM file system is placed at the end of the flash.
+For device with SPI flash the number for _sflash_fs might be 0 and
+the origin beyond the end of the flash. That does not matter since
+these devices do not use the MCU flash file system.
+*/
+
+_oflash_fs = ORIGIN(FLASH) + _codesize + _micropy_hw_romfs_part0_size;
+_sflash_fs = _flashsize - _codesize - _bootloader - _micropy_hw_romfs_part0_size;
+
+_micropy_hw_romfs_part0_start = ORIGIN(FLASH) + _codesize;

 _sheap = _ebss;
 _eheap = _sstack;
--- a/ports/samd/boards/samd51x19a.ld
+++ b/ports/samd/boards/samd51x19a.ld
@@ -3,8 +3,8 @@
 */

 /*
-_codesize is defined in mpconfigmcu.mk or mpconfigboard.mk as
-MICROPY_HW_CODESIZE and is set in Makefile
+_codesize and _micropy_hw_romfs_part0_size are defined in mpconfigmcu.mk or mpconfigboard.mk
+as MICROPY_HW_CODESIZE and MICROPY_HW_ROMFS_BYTES and are set in Makefile.
 */

 _flashsize = 512K;  /* The physical flash size */
@@ -21,8 +21,17 @@ MEMORY
 _estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
 _sstack = _estack - 16K;

-_oflash_fs = ORIGIN(FLASH) + _codesize;
-_sflash_fs = _flashsize - _codesize - _bootloader;
+/*
+The VfsROM file system is placed at the end of the flash.
+For device with SPI flash the number for _sflash_fs might be 0 and
+the origin beyond the end of the flash. That does not matter since
+these devices do not use the MCU flash file system.
+*/
+
+_oflash_fs = ORIGIN(FLASH) + _codesize + _micropy_hw_romfs_part0_size;
+_sflash_fs = _flashsize - _codesize - _bootloader - _micropy_hw_romfs_part0_size;
+
+_micropy_hw_romfs_part0_start = ORIGIN(FLASH) + _codesize;

 _sheap = _ebss;
 _eheap = _sstack;
--- a/ports/samd/boards/samd51x20a.ld
+++ b/ports/samd/boards/samd51x20a.ld
@@ -3,8 +3,8 @@
 */

 /*
-_codesize is defined in mpconfigmcu.mk or mpconfigboard.mk as
-MICROPY_HW_CODESIZE and is set in Makefile
+_codesize and _micropy_hw_romfs_part0_size are defined in mpconfigmcu.mk or mpconfigboard.mk
+as MICROPY_HW_CODESIZE and MICROPY_HW_ROMFS_BYTES and are set in Makefile.
 */

 _flashsize = 1024K; /* The physical flash size */
@@ -21,8 +21,17 @@ MEMORY
 _estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
 _sstack = _estack - 16K;

-_oflash_fs = ORIGIN(FLASH) + _codesize;
-_sflash_fs = _flashsize - _codesize - _bootloader;
+/*
+The VfsROM file system is placed at the end of the flash.
+For device with SPI flash the number for _sflash_fs might be 0 and
+the origin beyond the end of the flash. That does not matter since
+these devices do not use the MCU flash file system.
+*/
+
+_oflash_fs = ORIGIN(FLASH) + _codesize + _micropy_hw_romfs_part0_size;
+_sflash_fs = _flashsize - _codesize - _bootloader - _micropy_hw_romfs_part0_size;
+
+_micropy_hw_romfs_part0_start = ORIGIN(FLASH) + _codesize;

 _sheap = _ebss;
 _eheap = _sstack;
--- a/ports/samd/mcu/samd21/manifest.py
+++ b/ports/samd/mcu/samd21/manifest.py
@@ -1,5 +1,2 @@
 include("$(PORT_DIR)/boards/manifest.py")
 include("$(MPY_DIR)/extmod/asyncio")
-require("onewire")
-require("ds18x20")
-require("dht")
--- a/ports/samd/mcu/samd21/mpconfigmcu.h
+++ b/ports/samd/mcu/samd21/mpconfigmcu.h
@@ -2,11 +2,6 @@
 #include "samd21.h"

 #define MICROPY_CONFIG_ROM_LEVEL        (MICROPY_CONFIG_ROM_LEVEL_BASIC_FEATURES)
-#if MICROPY_HW_CODESIZE == 248
-#define SAMD21_EXTRA_FEATURES           1
-#else
-#define SAMD21_EXTRA_FEATURES           0
-#endif

 // MicroPython emitters
 #define MICROPY_EMIT_THUMB              (SAMD21_EXTRA_FEATURES)
--- a/ports/samd/mcu/samd21/mpconfigmcu.mk
+++ b/ports/samd/mcu/samd21/mpconfigmcu.mk
@@ -6,8 +6,13 @@ MPY_CROSS_MCU_ARCH = armv6m

 MICROPY_HW_CODESIZE ?= 184K

-ifeq ($(MICROPY_HW_CODESIZE), 248K)
+ifeq ($(MICROPY_HW_CODESIZE), 236K)
 FROZEN_MANIFEST ?= mcu/$(MCU_SERIES_LOWER)/manifest.py
+MICROPY_HW_ROMFS_BYTES ?= 12K
+CFLAGS_MCU += -DSAMD21_EXTRA_FEATURES=1
+else
+MICROPY_HW_ROMFS_BYTES ?= 0
+CFLAGS_MCU += -DSAMD21_EXTRA_FEATURES=0
 endif

 MICROPY_VFS_LFS1 ?= 1
--- a/ports/samd/mcu/samd51/manifest.py
+++ b/ports/samd/mcu/samd51/manifest.py
@@ -1,5 +1,2 @@
 include("$(PORT_DIR)/boards/manifest.py")
 include("$(MPY_DIR)/extmod/asyncio")
-require("onewire")
-require("ds18x20")
-require("dht")
--- a/ports/samd/mcu/samd51/mpconfigmcu.h
+++ b/ports/samd/mcu/samd51/mpconfigmcu.h
@@ -21,10 +21,10 @@ unsigned long trng_random_u32(void);
 #endif

 // fatfs configuration used in ffconf.h
-#define MICROPY_FATFS_ENABLE_LFN            (1)
-#define MICROPY_FATFS_RPATH                 (2)
-#define MICROPY_FATFS_MAX_SS                (4096)
-#define MICROPY_FATFS_LFN_CODE_PAGE         437 /* 1=SFN/ANSI 437=LFN/U.S.(OEM) */
+#define MICROPY_FATFS_ENABLE_LFN        (1)
+#define MICROPY_FATFS_RPATH             (2)
+#define MICROPY_FATFS_MAX_SS            (4096)
+#define MICROPY_FATFS_LFN_CODE_PAGE     437 /* 1=SFN/ANSI 437=LFN/U.S.(OEM) */

 #define VFS_BLOCK_SIZE_BYTES            (2048) //

--- a/ports/samd/mcu/samd51/mpconfigmcu.mk
+++ b/ports/samd/mcu/samd51/mpconfigmcu.mk
@@ -5,6 +5,7 @@ CFLAGS_MCU += -DCFG_TUSB_MCU=OPT_MCU_SAMD51
 MPY_CROSS_MCU_ARCH = armv7m

 MICROPY_HW_CODESIZE ?= 368K
+MICROPY_HW_ROMFS_BYTES ?= 64K

 MICROPY_VFS_LFS2 ?= 1
 MICROPY_VFS_FAT ?= 1
--- a/ports/samd/mpconfigport.h
+++ b/ports/samd/mpconfigport.h
@@ -86,6 +86,9 @@
 #define MICROPY_PY_OS_INCLUDEFILE           "ports/samd/modos.c"
 #define MICROPY_READER_VFS                  (1)
 #define MICROPY_VFS                         (1)
+#ifndef MICROPY_VFS_ROM
+#define MICROPY_VFS_ROM                     (1)
+#endif
 #ifndef MICROPY_PY_MACHINE_ADC
 #define MICROPY_PY_MACHINE_ADC              (1)
 #endif
--- a/ports/samd/samd_flash.c
+++ b/ports/samd/samd_flash.c
@@ -26,11 +26,13 @@

 #include <stdio.h>

+#include "py/objarray.h"
 #include "py/runtime.h"
 #include "extmod/vfs.h"
+#include "py/mperrno.h"
 #include "samd_soc.h"

-#if MICROPY_HW_MCUFLASH
+#if MICROPY_HW_MCUFLASH || MICROPY_VFS_ROM

 // ASF 4
 #include "hal_flash.h"
@@ -45,7 +47,6 @@
 #endif

 static struct flash_descriptor flash_desc;
-static mp_int_t BLOCK_SIZE = VFS_BLOCK_SIZE_BYTES; // Board specific: mpconfigboard.h
 extern const mp_obj_type_t samd_flash_type;

 typedef struct _samd_flash_obj_t {
@@ -54,8 +55,9 @@ typedef struct _samd_flash_obj_t {
    uint32_t flash_size;
 } samd_flash_obj_t;

+#if MICROPY_HW_MCUFLASH
+static mp_int_t BLOCK_SIZE = VFS_BLOCK_SIZE_BYTES; // Board specific: mpconfigboard.h
 extern uint8_t _oflash_fs, _sflash_fs;
-
 // Build a Flash storage at top.
 static samd_flash_obj_t samd_flash_obj = {
    .base = { &samd_flash_type },
@@ -63,9 +65,31 @@ static samd_flash_obj_t samd_flash_obj = {
    .flash_size = (uint32_t)&_sflash_fs, // Get from MCU-Specific loader script.
 };

+static mp_obj_t samd_flash_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    // No args required. bdev=Flash(). Start Addr & Size defined in samd_flash_obj.
+    mp_arg_check_num(n_args, n_kw, 0, 0, false);
+
+    // Return singleton object.
+    return MP_OBJ_FROM_PTR(&samd_flash_obj);
+}
+
+static mp_int_t samd_flash_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
+    samd_flash_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    if (flags == MP_BUFFER_READ) {
+        bufinfo->buf = (void *)((uintptr_t)self->flash_base);
+        bufinfo->len = self->flash_size;
+        bufinfo->typecode = 'B';
+        return 0;
+    } else {
+        // Write unsupported.
+        return 1;
+    }
+}
+#endif  // MICROPY_HW_MCUFLASH
+
 // Flash init (from cctpy)
 // Method is needed for when MP starts up in _boot.py
-static void samd_flash_init(void) {
+void samd_flash_init(void) {
    #ifdef SAMD51
    hri_mclk_set_AHBMASK_NVMCTRL_bit(MCLK);
    #endif
@@ -76,23 +100,14 @@ static void samd_flash_init(void) {
    flash_init(&flash_desc, NVMCTRL);
 }

-static mp_obj_t samd_flash_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
-    // No args required. bdev=Flash(). Start Addr & Size defined in samd_flash_obj.
-    mp_arg_check_num(n_args, n_kw, 0, 0, false);
-
-    samd_flash_init();
-
-    // Return singleton object.
-    return MP_OBJ_FROM_PTR(&samd_flash_obj);
-}
-
+#if MICROPY_HW_MCUFLASH
 // Function for ioctl.
 static mp_obj_t eraseblock(uint32_t sector_in) {
    // Destination address aligned with page start to be erased.
-    uint32_t DEST_ADDR = sector_in; // Number of pages to be erased.
-    mp_int_t PAGE_SIZE = flash_get_page_size(&flash_desc); // adf4 API call
+    uint32_t dest_addr = sector_in; // Number of pages to be erased.
+    mp_int_t page_size = flash_get_page_size(&flash_desc); // adf4 API call

-    flash_erase(&flash_desc, DEST_ADDR, (BLOCK_SIZE / PAGE_SIZE));
+    flash_erase(&flash_desc, dest_addr, (BLOCK_SIZE / page_size));

    return mp_const_none;
 }
@@ -131,7 +146,7 @@ static mp_obj_t samd_flash_writeblocks(size_t n_args, const mp_obj_t *args) {
    }
    // Write data to flash (adf4 API)
    flash_write(&flash_desc, offset, bufinfo.buf, bufinfo.len);
-    // TODO check return value
+
    return mp_const_none;
 }
 static MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(samd_flash_writeblocks_obj, 3, 4, samd_flash_writeblocks);
@@ -176,7 +191,75 @@ MP_DEFINE_CONST_OBJ_TYPE(
    MP_QSTR_Flash,
    MP_TYPE_FLAG_NONE,
    make_new, samd_flash_make_new,
+    buffer, samd_flash_get_buffer,
    locals_dict, &samd_flash_locals_dict
    );
+#endif

-#endif  // MICROPY_HW_MCUFLASH
+#if MICROPY_VFS_ROM
+//
+// Uses object-based capabilities for devices using the internal flash
+// for the regular file system and ioctl function for devices with
+// external flash.
+//
+extern uint8_t _micropy_hw_romfs_part0_start, _micropy_hw_romfs_part0_size;
+
+#define MICROPY_HW_ROMFS_BASE ((uint32_t)&_micropy_hw_romfs_part0_start)
+#define MICROPY_HW_ROMFS_BYTES ((uint32_t)&_micropy_hw_romfs_part0_size)
+
+#if MICROPY_HW_MCUFLASH
+static samd_flash_obj_t samd_flash_romfs_obj = {
+    .base = { &samd_flash_type },
+    .flash_base = MICROPY_HW_ROMFS_BASE, // Get from MCU-Specific loader script.
+    .flash_size = MICROPY_HW_ROMFS_BYTES, // Get from MCU-Specific loader script.
+};
+#else
+static const MP_DEFINE_MEMORYVIEW_OBJ(samd_flash_romfs_obj, 'B', 0, MICROPY_HW_ROMFS_BYTES, (void *)MICROPY_HW_ROMFS_BASE);
+#endif
+
+mp_obj_t mp_vfs_rom_ioctl(size_t n_args, const mp_obj_t *args) {
+    if (MICROPY_HW_ROMFS_BYTES <= 0) {
+        return MP_OBJ_NEW_SMALL_INT(-MP_EINVAL);
+    }
+    switch (mp_obj_get_int(args[0])) {
+        case MP_VFS_ROM_IOCTL_GET_NUMBER_OF_SEGMENTS:
+            return MP_OBJ_NEW_SMALL_INT(1);
+
+        case MP_VFS_ROM_IOCTL_GET_SEGMENT:
+            return MP_OBJ_FROM_PTR(&samd_flash_romfs_obj);
+
+            #if !MICROPY_HW_MCUFLASH
+
+        case MP_VFS_ROM_IOCTL_WRITE_PREPARE: {
+            // Erase sectors in given range.
+            if (n_args < 3) {
+                return MP_OBJ_NEW_SMALL_INT(-MP_EINVAL);
+            }
+            uint32_t dest_addr = MICROPY_HW_ROMFS_BASE;
+            uint32_t bytes_used = mp_obj_get_int(args[2]);
+            mp_int_t page_size = flash_get_page_size(&flash_desc); // adf4 API call
+            flash_erase(&flash_desc, dest_addr, (bytes_used + page_size - 1) / page_size);
+            return MP_OBJ_NEW_SMALL_INT(4);
+        }
+
+        case MP_VFS_ROM_IOCTL_WRITE: {
+            // Write data to flash.
+            if (n_args < 4) {
+                return MP_OBJ_NEW_SMALL_INT(-MP_EINVAL);
+            }
+            uint32_t dest_addr = MICROPY_HW_ROMFS_BASE + mp_obj_get_int(args[2]);
+            mp_buffer_info_t bufinfo;
+            mp_get_buffer_raise(args[3], &bufinfo, MP_BUFFER_READ);
+            flash_write(&flash_desc, dest_addr, bufinfo.buf, bufinfo.len);
+            return MP_OBJ_NEW_SMALL_INT(0);
+        }
+
+            #endif
+
+        default:
+            return MP_OBJ_NEW_SMALL_INT(-MP_EINVAL);
+    }
+}
+#endif
+
+#endif  // MICROPY_HW_MCUFLASH || MICROPY_VFS_ROM
--- a/ports/samd/samd_soc.c
+++ b/ports/samd/samd_soc.c
@@ -39,6 +39,7 @@
 #include "tusb.h"

 extern void machine_rtc_start(bool force);
+extern void samd_flash_init(void);

 static void usb_init(void) {
    // Init USB clock
@@ -120,6 +121,9 @@ void samd_init(void) {
    mp_hal_ticks_cpu_enable();
    #endif
    machine_rtc_start(false);
+    #if MICROPY_HW_MCUFLASH || MICROPY_VFS_ROM
+    samd_flash_init();
+    #endif
 }

 #if MICROPY_PY_MACHINE_I2C || MICROPY_PY_MACHINE_I2C_TARGET || MICROPY_PY_MACHINE_SPI || MICROPY_PY_MACHINE_UART