diff --git a/bootloaders/eboot/Makefile b/bootloaders/eboot/Makefile
index e078263caa..3e25eb139e 100644
--- a/bootloaders/eboot/Makefile
+++ b/bootloaders/eboot/Makefile
@@ -17,11 +17,13 @@ AR := $(XTENSA_TOOLCHAIN)xtensa-lx106-elf-ar
 LD := $(XTENSA_TOOLCHAIN)xtensa-lx106-elf-gcc
 OBJDUMP := $(XTENSA_TOOLCHAIN)xtensa-lx106-elf-objdump
 
-
+INC += -I../../tools/sdk/include
 CFLAGS += -std=gnu99
 
 CFLAGS += -O0 -g -Wpointer-arith -Wno-implicit-function-declaration -Wl,-EL -fno-inline-functions -nostdlib -mlongcalls -mno-text-section-literals
 
+CFLAGS += $(INC)
+
 LDFLAGS	+= -nostdlib -Wl,--no-check-sections -umain
 
 LD_SCRIPT := -Teboot.ld
diff --git a/bootloaders/eboot/eboot.elf b/bootloaders/eboot/eboot.elf
index 1ccbe25fc3..da0f845278 100755
Binary files a/bootloaders/eboot/eboot.elf and b/bootloaders/eboot/eboot.elf differ
diff --git a/bootloaders/eboot/flash.h b/bootloaders/eboot/flash.h
index ea8b65c1fa..38c528869a 100644
--- a/bootloaders/eboot/flash.h
+++ b/bootloaders/eboot/flash.h
@@ -8,15 +8,19 @@
 #ifndef FLASH_H
 #define FLASH_H
 
+
+/* The geometry defines are placed in the sdk. The .h was factored out for reuse by eboot here.
+ * Beware: this means that eboot has an external dependency.
+ * The following .h is placed in tools/sdk/includes
+ */
+#include <spi_flash_geometry.h>
+
 int SPIEraseBlock(uint32_t block);
 int SPIEraseSector(uint32_t sector);
 int SPIRead(uint32_t addr, void *dest, size_t size);
 int SPIWrite(uint32_t addr, void *src, size_t size);
 int SPIEraseAreaEx(const uint32_t start, const uint32_t size);
 
-#define FLASH_SECTOR_SIZE 0x1000
-#define FLASH_BLOCK_SIZE 0x10000
-#define APP_START_OFFSET 0x1000
 
 typedef struct {
     unsigned char       magic;
@@ -25,7 +29,7 @@ typedef struct {
     /* SPI Flash Interface (0 = QIO, 1 = QOUT, 2 = DIO, 0x3 = DOUT) */
     unsigned char       flash_mode;
 
-    /* High four bits: 0 = 512K, 1 = 256K, 2 = 1M, 3 = 2M, 4 = 4M, 
+    /* High four bits: 0 = 512K, 1 = 256K, 2 = 1M, 3 = 2M, 4 = 4M, 8 = 8M, 9 = 16M
        Low four bits:  0 = 40MHz, 1= 26MHz, 2 = 20MHz, 0xf = 80MHz */
     unsigned char		flash_size_freq;
 
diff --git a/cores/esp8266/flash_utils.h b/cores/esp8266/flash_utils.h
index 67dc6ebadd..eade691a5b 100644
--- a/cores/esp8266/flash_utils.h
+++ b/cores/esp8266/flash_utils.h
@@ -21,39 +21,17 @@
 #ifndef FLASH_UTILS_H
 #define FLASH_UTILS_H
 
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-int SPIEraseBlock(uint32_t block);
-int SPIEraseSector(uint32_t sector);
-int SPIRead(uint32_t addr, void *dest, size_t size);
-int SPIWrite(uint32_t addr, void *src, size_t size);
-int SPIEraseAreaEx(const uint32_t start, const uint32_t size);
-
-#define FLASH_SECTOR_SIZE 0x1000
-#define FLASH_BLOCK_SIZE 0x10000
-#define APP_START_OFFSET 0x1000
-
-typedef struct {
-    unsigned char       magic;
-    unsigned char       num_segments;
-
-    /* SPI Flash Interface (0 = QIO, 1 = QOUT, 2 = DIO, 0x3 = DOUT) */
-    unsigned char       flash_mode;
-
-    /* High four bits: 0 = 512K, 1 = 256K, 2 = 1M, 3 = 2M, 4 = 4M, 8 = 8M, 9 = 16M
-       Low four bits:  0 = 40MHz, 1= 26MHz, 2 = 20MHz, 0xf = 80MHz */
-    unsigned char		flash_size_freq;
-
-    uint32_t            entry;
-} image_header_t;
-
+/* Definitions are placed in eboot. Include them here rather than duplicate them.
+ * Also, prefer to have eboot standalone as much as possible and have the core depend on it
+ * rather than have eboot depend on the core.
+ */
+#include <../../bootloaders/eboot/flash.h>
 
-typedef struct {
-    uint32_t            address;
-    uint32_t            size;
-} section_header_t;
 
 #ifdef __cplusplus
 }
diff --git a/tools/sdk/include/spi_flash.h b/tools/sdk/include/spi_flash.h
index 00f8a08b79..4e5a94f831 100644
--- a/tools/sdk/include/spi_flash.h
+++ b/tools/sdk/include/spi_flash.h
@@ -25,6 +25,8 @@
 #ifndef SPI_FLASH_H
 #define SPI_FLASH_H
 
+#include <spi_flash_geometry.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -44,8 +46,6 @@ typedef struct{
 	uint32  status_mask;
 } SpiFlashChip;
 
-#define SPI_FLASH_SEC_SIZE      4096
-
 extern SpiFlashChip * flashchip; // in ram ROM-BIOS
 
 uint32 spi_flash_get_id(void);
diff --git a/tools/sdk/include/spi_flash_geometry.h b/tools/sdk/include/spi_flash_geometry.h
new file mode 100644
index 0000000000..bb8c0ea22f
--- /dev/null
+++ b/tools/sdk/include/spi_flash_geometry.h
@@ -0,0 +1,15 @@
+#ifndef SPI_FLASH_GEOMETRY_H
+#define SPI_FLASH_GEOMETRY_H
+
+/* The flash geometry is meant to be unified here. This header file should be included wherever needed.
+ * Beware: this file is needed by eboot as well as the Arduino core.
+ */
+
+#define FLASH_SECTOR_SIZE 0x1000
+#define FLASH_BLOCK_SIZE 0x10000
+#define APP_START_OFFSET 0x1000
+
+//pulled this define from spi_flash.h for reuse in the Arduino core without pulling in a bunch of other stuff
+#define SPI_FLASH_SEC_SIZE      FLASH_SECTOR_SIZE
+
+#endif
diff --git a/tools/sdk/include/upgrade.h b/tools/sdk/include/upgrade.h
index 6c88f9a043..8d5f6cd7cf 100644
--- a/tools/sdk/include/upgrade.h
+++ b/tools/sdk/include/upgrade.h
@@ -29,8 +29,8 @@
 extern "C" {
 #endif
 
+#include <spi_flash_geometry.h>
 
-#define SPI_FLASH_SEC_SIZE      4096
 #define LIMIT_ERASE_SIZE		0x10000
 
 #define USER_BIN1               0x00