diff --git a/ports/samd/Makefile b/ports/samd/Makefile
index 290453f50b..6f7c8fbd85 100644
--- a/ports/samd/Makefile
+++ b/ports/samd/Makefile
@@ -65,7 +65,10 @@ CFLAGS += $(INC) -Wall -Werror -std=c99 -nostdlib -mthumb $(CFLAGS_MCU) -fsingle
 CFLAGS += -DMCU_$(MCU_SERIES) -D__$(CMSIS_MCU)__
 CFLAGS += $(CFLAGS_EXTRA)
 
+CFLAGS += -DMICROPY_HW_CODESIZE=$(MICROPY_HW_CODESIZE)
+
 LDFLAGS += -nostdlib $(addprefix -T,$(LD_FILES)) -Map=$@.map --cref
+LDFLAGS += --defsym=_codesize=$(MICROPY_HW_CODESIZE)
 
 LIBS += $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
 
diff --git a/ports/samd/boards/samd21x18a.ld b/ports/samd/boards/samd21x18a.ld
index 81a84a15d7..3ab051569f 100644
--- a/ports/samd/boards/samd21x18a.ld
+++ b/ports/samd/boards/samd21x18a.ld
@@ -2,10 +2,18 @@
     GNU linker script for SAMD21
 */
 
+/*
+_codesize is defined in mpconfigmcu.mk or mpconfigboard.mk as
+MICROPY_HW_CODESIZE and is set in Makefile
+*/
+
+_flashsize = 256K;  /* The physical flash size */
+_bootloader = 8K;   /* Must match the ORIGIN value of FLASH */
+
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx)  : ORIGIN = 0x00002000, LENGTH = 256K - 8K
+    FLASH (rx)  : ORIGIN = 0x00002000, LENGTH = _codesize
     RAM (xrw)   : ORIGIN = 0x20000000, LENGTH = 32K
 }
 
@@ -13,8 +21,8 @@ MEMORY
 _estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
 _sstack = _estack - 8K;
 
-_oflash_fs = ORIGIN(FLASH) + 192K - 8K;
-_sflash_fs = LENGTH(FLASH) - 192K + 8K - 1;
+_oflash_fs = ORIGIN(FLASH) + _codesize;
+_sflash_fs = _flashsize - _codesize - _bootloader;
 
 _sheap = _ebss;
 _eheap = _sstack;
diff --git a/ports/samd/boards/samd51x19a.ld b/ports/samd/boards/samd51x19a.ld
index cd03320ba4..30bc8e3328 100644
--- a/ports/samd/boards/samd51x19a.ld
+++ b/ports/samd/boards/samd51x19a.ld
@@ -2,10 +2,18 @@
     GNU linker script for SAMD51
 */
 
+/*
+_codesize is defined in mpconfigmcu.mk or mpconfigboard.mk as
+MICROPY_HW_CODESIZE and is set in Makefile
+*/
+
+_flashsize = 512K;  /* The physical flash size */
+_bootloader = 16K;  /* Must match the ORIGIN value of FLASH */
+
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx)  : ORIGIN = 0x00004000, LENGTH = 512K - 16K
+    FLASH (rx)  : ORIGIN = 0x00004000, LENGTH = _codesize
     RAM (xrw)   : ORIGIN = 0x20000000, LENGTH = 192K
 }
 
@@ -13,8 +21,8 @@ MEMORY
 _estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
 _sstack = _estack - 16K;
 
-_oflash_fs = ORIGIN(FLASH) + 384K - 16K;
-_sflash_fs = LENGTH(FLASH) - 384K + 16K - 1;
+_oflash_fs = ORIGIN(FLASH) + _codesize;
+_sflash_fs = _flashsize - _codesize - _bootloader;
 
 _sheap = _ebss;
 _eheap = _sstack;
diff --git a/ports/samd/boards/samd51x20a.ld b/ports/samd/boards/samd51x20a.ld
index f0d5e5c6ae..472ab316c6 100644
--- a/ports/samd/boards/samd51x20a.ld
+++ b/ports/samd/boards/samd51x20a.ld
@@ -2,10 +2,18 @@
     GNU linker script for SAMD51x20
 */
 
+/*
+_codesize is defined in mpconfigmcu.mk or mpconfigboard.mk as
+MICROPY_HW_CODESIZE and is set in Makefile
+*/
+
+_flashsize = 1024K; /* The physical flash size */
+_bootloader = 16K;  /* Must match the ORIGIN value of FLASH */
+
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx)  : ORIGIN = 0x00004000, LENGTH = 1024K - 16K
+    FLASH (rx)  : ORIGIN = 0x00004000, LENGTH = _codesize
     RAM (xrw)   : ORIGIN = 0x20000000, LENGTH = 256K
 }
 
@@ -13,8 +21,8 @@ MEMORY
 _estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
 _sstack = _estack - 16K;
 
-_oflash_fs = ORIGIN(FLASH) + 384K - 16K;
-_sflash_fs = LENGTH(FLASH) - 384K + 16K - 1;
+_oflash_fs = ORIGIN(FLASH) + _codesize;
+_sflash_fs = _flashsize - _codesize - _bootloader;
 
 _sheap = _ebss;
 _eheap = _sstack;
diff --git a/ports/samd/mcu/samd21/mpconfigmcu.mk b/ports/samd/mcu/samd21/mpconfigmcu.mk
index ddd3e8b410..2e16d12a2d 100644
--- a/ports/samd/mcu/samd21/mpconfigmcu.mk
+++ b/ports/samd/mcu/samd21/mpconfigmcu.mk
@@ -2,6 +2,8 @@ CFLAGS_MCU += -mtune=cortex-m0plus -mcpu=cortex-m0plus -msoft-float
 
 MPY_CROSS_MCU_ARCH = armv6m
 
+MICROPY_HW_CODESIZE ?= 184K
+
 SRC_S += shared/runtime/gchelper_thumb1.s
 
 LIBM_SRC_C +=  $(addprefix lib/libm/,\
diff --git a/ports/samd/mcu/samd51/mpconfigmcu.mk b/ports/samd/mcu/samd51/mpconfigmcu.mk
index 8596f59821..433404fd11 100644
--- a/ports/samd/mcu/samd51/mpconfigmcu.mk
+++ b/ports/samd/mcu/samd51/mpconfigmcu.mk
@@ -2,6 +2,8 @@ CFLAGS_MCU += -mtune=cortex-m4 -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=har
 
 MPY_CROSS_MCU_ARCH = armv7m
 
+MICROPY_HW_CODESIZE ?= 368K
+
 MICROPY_VFS_LFS2 ?= 1
 MICROPY_VFS_FAT ?= 1
 FROZEN_MANIFEST ?= mcu/$(MCU_SERIES_LOWER)/manifest.py