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

robert-hh · dpgeorge · commit c07b178dbda6 · 2026-01-02T15:23:49.000+11:00
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 &lt;damien@micropython.org&gt;
Signed-off-by: robert-hh &lt;robert@hammelrath.com&gt;
diff --git 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))
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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
diff --git 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;
diff --git 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;
diff --git 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;
diff --git 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")
diff --git 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)
diff --git 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
diff --git 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")
diff --git 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) //
 
diff --git 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
diff --git 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
diff --git a/ports/samd/samd_flash.c b/ports/samd/samd_flash.c
diff --git a/ports/samd/samd_soc.c b/ports/samd/samd_soc.c

Original file line number	Diff line number	Diff line change
`@@ -1,2 +1,2 @@`
`1`	`1`	`CFLAGS += -DMICROPY_HW_SPIFLASH=1`
`2`		`-MICROPY_HW_CODESIZE ?= 232K`
	`2`	`+MICROPY_HW_CODESIZE ?= 236K`