diff --git a/Makefile b/Makefile
index ccf379f..d4a215c 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,6 @@
 # Makefile heavily adapted to esp-link and wireless flashing by Thorsten von Eicken
 # Lots of work, in particular to support windows, by brunnels
 # Original from esphttpd and others...
-# VERBOSE=1
 #
 # Start by setting the directories for the toolchain a few lines down
 # the default target will build the firmware images
@@ -52,35 +51,37 @@ ESP_HOSTNAME  ?= esp-link
 
 # Base directory for the compiler. Needs a / at the end.
 # Typically you'll install https://github.com/pfalcon/esp-open-sdk
+# IMPORTANT: use esp-open-sdk `make STANDALONE=n`: the SDK bundled with esp-open-sdk will *not* work!
 XTENSA_TOOLS_ROOT ?= $(abspath ../esp-open-sdk/xtensa-lx106-elf/bin)/
 
 # Firmware version 
 # WARNING: if you change this expect to make code adjustments elsewhere, don't expect
 # that esp-link will magically work with a different version of the SDK!!!
-SDK_VERS ?= esp_iot_sdk_v1.5.4
+SDK_VERS ?= esp_iot_sdk_v2.0.0.p1
 
 # Try to find the firmware manually extracted, e.g. after downloading from Espressif's BBS,
 # http://bbs.espressif.com/viewforum.php?f=46
 SDK_BASE ?= $(wildcard ../$(SDK_VERS))
 
 # If the firmware isn't there, see whether it got downloaded as part of esp-open-sdk
-ifeq ($(SDK_BASE),)
-SDK_BASE := $(wildcard $(XTENSA_TOOLS_ROOT)/../../$(SDK_VERS))
-endif
+# This used to work at some point, but is not supported, uncomment if you feel lucky ;-)
+#ifeq ($(SDK_BASE),)
+#SDK_BASE := $(wildcard $(XTENSA_TOOLS_ROOT)/../../$(SDK_VERS))
+#endif
 
 # Clean up SDK path
 SDK_BASE := $(abspath $(SDK_BASE))
 $(warning Using SDK from $(SDK_BASE))
 
 # Path to bootloader file
-BOOTFILE	?= $(SDK_BASE/bin/boot_v1.5.bin)
+BOOTFILE	?= $(SDK_BASE/bin/boot_v1.6.bin)
 
 # Esptool.py path and port, only used for 1-time serial flashing
 # Typically you'll use https://github.com/themadinventor/esptool
 # Windows users use the com port i.e: ESPPORT ?= com3
 ESPTOOL		?= $(abspath ../esp-open-sdk/esptool/esptool.py)
 ESPPORT		?= /dev/ttyUSB0
-ESPBAUD		?= 460800
+ESPBAUD		?= 230400
 
 # --------------- chipset configuration   ---------------
 
@@ -117,8 +118,6 @@ MODULES ?= mqtt rest syslog web-server
 #
 # Adding JPG or PNG files (and any other compressed formats) is not recommended, because GZIP
 # compression does not work effectively on compressed files.
-
-#Static gzipping is disabled by default.
 GZIP_COMPRESSION ?= yes
 
 # If COMPRESS_W_HTMLCOMPRESSOR is set to "yes" then the static css and js files will be compressed with
@@ -226,8 +225,8 @@ endif
 
 # which modules (subdirectories) of the project to include in compiling
 LIBRARIES_DIR 	= libraries
-MODULES		  	+= espfs httpd user serial cmd esp-link
-MODULES			+= $(foreach sdir,$(LIBRARIES_DIR),$(wildcard $(sdir)/*))
+MODULES		+= espfs httpd user serial cmd esp-link
+MODULES		+= $(foreach sdir,$(LIBRARIES_DIR),$(wildcard $(sdir)/*))
 EXTRA_INCDIR 	= include .
 
 # libraries used in this project, mainly provided by the SDK
@@ -250,18 +249,17 @@ LD_SCRIPT1	:= build/eagle.esphttpd1.v6.ld
 LD_SCRIPT2	:= build/eagle.esphttpd2.v6.ld
 
 # various paths from the SDK used in this project
-SDK_LIBDIR		= lib
-SDK_LDDIR		= ld
-SDK_INCDIR		= include include/json
+SDK_LIBDIR	= lib
+SDK_LDDIR	= ld
+SDK_INCDIR	= include include/json
 SDK_TOOLSDIR	= tools
 
 # select which tools to use as compiler, librarian and linker
 CC		:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-gcc
 AR		:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-ar
 LD		:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-gcc
-OBJCP	:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-objcopy
-OBJDP	:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-objdump
-
+OBJCP		:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-objcopy
+OBJDP		:= $(XTENSA_TOOLS_ROOT)xtensa-lx106-elf-objdump
 
 ####
 SRC_DIR		:= $(MODULES)
@@ -273,14 +271,14 @@ SDK_INCDIR	:= $(addprefix -I$(SDK_BASE)/,$(SDK_INCDIR))
 SDK_TOOLS	:= $(addprefix $(SDK_BASE)/,$(SDK_TOOLSDIR))
 APPGEN_TOOL	:= $(addprefix $(SDK_TOOLS)/,$(APPGEN_TOOL))
 
-SRC			:= $(foreach sdir,$(SRC_DIR),$(wildcard $(sdir)/*.c))
-OBJ			:= $(patsubst %.c,$(BUILD_BASE)/%.o,$(SRC)) $(BUILD_BASE)/espfs_img.o
+SRC		:= $(foreach sdir,$(SRC_DIR),$(wildcard $(sdir)/*.c))
+OBJ		:= $(patsubst %.c,$(BUILD_BASE)/%.o,$(SRC)) $(BUILD_BASE)/espfs_img.o
 LIBS		:= $(addprefix -l,$(LIBS))
 APP_AR		:= $(addprefix $(BUILD_BASE)/,$(TARGET)_app.a)
 USER1_OUT 	:= $(addprefix $(BUILD_BASE)/,$(TARGET).user1.out)
 USER2_OUT 	:= $(addprefix $(BUILD_BASE)/,$(TARGET).user2.out)
 
-INCDIR			:= $(addprefix -I,$(SRC_DIR))
+INCDIR		:= $(addprefix -I,$(SRC_DIR))
 EXTRA_INCDIR	:= $(addprefix -I,$(EXTRA_INCDIR))
 MODULE_INCDIR	:= $(addsuffix /include,$(INCDIR))
 
@@ -381,7 +379,7 @@ $(FW_BASE)/user2.bin: $(USER2_OUT) $(FW_BASE)
 	$(Q) $(OBJCP) --only-section .data -O binary $(USER2_OUT) eagle.app.v6.data.bin
 	$(Q) $(OBJCP) --only-section .rodata -O binary $(USER2_OUT) eagle.app.v6.rodata.bin
 	$(Q) $(OBJCP) --only-section .irom0.text -O binary $(USER2_OUT) eagle.app.v6.irom0text.bin
-	$(Q) COMPILE=gcc PATH=$(XTENSA_TOOLS_ROOT):$(PATH) python $(APPGEN_TOOL) $(USER2_OUT) 2 $(ESP_FLASH_MODE) $(ESP_FLASH_FREQ_DIV) $(ESP_SPI_SIZE) 0
+	$(Q) COMPILE=gcc PATH=$(XTENSA_TOOLS_ROOT):$(PATH) python $(APPGEN_TOOL) $(USER2_OUT) 2 $(ESP_FLASH_MODE) $(ESP_FLASH_FREQ_DIV) $(ESP_SPI_SIZE) 1
 	$(Q) rm -f eagle.app.v6.*.bin
 	$(Q) mv eagle.app.flash.bin $@
 	$(Q) if [ $$(stat -c '%s' $@) -gt $$(( $(ESP_FLASH_MAX) )) ]; then echo "$@ too big!"; false; fi
@@ -430,23 +428,23 @@ $(BUILD_BASE)/espfs_img.o: html/ html/wifi/ espfs/mkespfsimage/mkespfsimage
 	$(Q) cp -r html/wifi/*.png html_compressed/wifi;
 	$(Q) cp -r html/wifi/*.js html_compressed/wifi;
 ifeq ("$(COMPRESS_W_HTMLCOMPRESSOR)","yes")
-	$(Q) echo "Compression assets with htmlcompressor. This may take a while..."
-		$(Q) java -jar tools/$(HTML_COMPRESSOR) \
-		-t html --remove-surrounding-spaces max --remove-quotes --remove-intertag-spaces \
-		-o $(abspath ./html_compressed)/ \
-		$(HTML_PATH)head- \
-		$(HTML_PATH)*.html
+	$(Q) echo "Compressing assets with htmlcompressor. This may take a while..."
+	$(Q) java -jar tools/$(HTML_COMPRESSOR) \
+	  -t html --remove-surrounding-spaces max --remove-quotes --remove-intertag-spaces \
+	  -o $(abspath ./html_compressed)/ \
+	  $(HTML_PATH)head- \
+	  $(HTML_PATH)*.html
 	$(Q) java -jar tools/$(HTML_COMPRESSOR) \
-		-t html --remove-surrounding-spaces max --remove-quotes --remove-intertag-spaces \
-		-o $(abspath ./html_compressed)/wifi/ \
-		$(WIFI_PATH)*.html
-	$(Q) echo "Compression assets with yui-compressor. This may take a while..."
+	  -t html --remove-surrounding-spaces max --remove-quotes --remove-intertag-spaces \
+	  -o $(abspath ./html_compressed)/wifi/ \
+	  $(WIFI_PATH)*.html
+	$(Q) echo "Compressing assets with yui-compressor. This may take a while..."
 	$(Q) for file in `find html_compressed -type f -name "*.js"`; do \
-			java -jar tools/$(YUI_COMPRESSOR) $$file --line-break 0 -o $$file; \
-		done
+	    java -jar tools/$(YUI_COMPRESSOR) $$file --line-break 0 -o $$file; \
+	  done
 	$(Q) for file in `find html_compressed -type f -name "*.css"`; do \
-			java -jar tools/$(YUI_COMPRESSOR) $$file -o $$file; \
-		done
+	    java -jar tools/$(YUI_COMPRESSOR) $$file -o $$file; \
+	  done
 else
 	$(Q) cp -r html/head- html_compressed;
 	$(Q) cp -r html/*.html html_compressed;
@@ -457,25 +455,25 @@ ifeq (,$(findstring mqtt,$(MODULES)))
 	$(Q) rm -rf html_compressed/mqtt.js
 endif
 	$(Q) for file in `find html_compressed -type f -name "*.htm*"`; do \
-		cat html_compressed/head- $$file >$${file}-; \
-		mv $$file- $$file; \
-	done
+	    cat html_compressed/head- $$file >$${file}-; \
+	    mv $$file- $$file; \
+	  done
 	$(Q) rm html_compressed/head-
 	$(Q) cd html_compressed; find . \! -name \*- | ../espfs/mkespfsimage/mkespfsimage > ../build/espfs.img; cd ..;
 	$(Q) ls -sl build/espfs.img
 	$(Q) cd build; $(OBJCP) -I binary -O elf32-xtensa-le -B xtensa --rename-section .data=.espfs \
-			espfs.img espfs_img.o; cd ..
+	  espfs.img espfs_img.o; cd ..
 
 # edit the loader script to add the espfs section to the end of irom with a 4 byte alignment.
 # we also adjust the sizes of the segments 'cause we need more irom0
 build/eagle.esphttpd1.v6.ld: $(SDK_LDDIR)/eagle.app.v6.new.1024.app1.ld
 	$(Q) sed -e '/\.irom\.text/{' -e 'a . = ALIGN (4);' -e 'a *(.espfs)' -e '}'  \
-			-e '/^  irom0_0_seg/ s/6B000/7C000/' \
-			$(SDK_LDDIR)/eagle.app.v6.new.1024.app1.ld >$@
+		-e '/^  irom0_0_seg/ s/6B000/7C000/' \
+		$(SDK_LDDIR)/eagle.app.v6.new.1024.app1.ld >$@
 build/eagle.esphttpd2.v6.ld: $(SDK_LDDIR)/eagle.app.v6.new.1024.app2.ld
 	$(Q) sed -e '/\.irom\.text/{' -e 'a . = ALIGN (4);' -e 'a *(.espfs)' -e '}'  \
-			-e '/^  irom0_0_seg/ s/6B000/7C000/' \
-			$(SDK_LDDIR)/eagle.app.v6.new.1024.app2.ld >$@
+		-e '/^  irom0_0_seg/ s/6B000/7C000/' \
+		$(SDK_LDDIR)/eagle.app.v6.new.1024.app2.ld >$@
 
 espfs/mkespfsimage/mkespfsimage: espfs/mkespfsimage/
 	$(Q) $(MAKE) -C espfs/mkespfsimage GZIP_COMPRESSION="$(GZIP_COMPRESSION)"
diff --git a/esp-link/main.c b/esp-link/main.c
index 4c04efa..e775de9 100644
--- a/esp-link/main.c
+++ b/esp-link/main.c
@@ -122,13 +122,30 @@ extern uint32_t _binary_espfs_img_start;
 extern void app_init(void);
 extern void mqtt_client_init(void);
 
-void user_rf_pre_init(void) {
+void ICACHE_FLASH_ATTR
+user_rf_pre_init(void) {
   //default is enabled
   system_set_os_print(DEBUG_SDK);
 }
 
+/* user_rf_cal_sector_set is a required function that is called by the SDK to get a flash
+ * sector number where it can store RF calibration data. This was introduced with SDK 1.5.4.1
+ * and is necessary because Espressif ran out of pre-reserved flash sectors. Ooops...  */
+uint32 ICACHE_FLASH_ATTR
+user_rf_cal_sector_set(void) {
+  uint32_t sect = 0;
+  switch (system_get_flash_size_map()) {
+  case FLASH_SIZE_4M_MAP_256_256: // 512KB
+    sect = 128 - 10; // 0x76000
+  default:
+    sect = 128; // 0x80000
+  }
+  return sect;
+}
+
 // Main routine to initialize esp-link.
-void user_init(void) {
+void ICACHE_FLASH_ATTR
+user_init(void) {
   // uncomment the following three lines to see flash config messages for troubleshooting
   //uart_init(115200, 115200);
   //logInit();
@@ -154,13 +171,13 @@ void user_init(void) {
   wifiInit();
   // init the flash filesystem with the html stuff
   espFsInit(espLinkCtx, &_binary_espfs_img_start, ESPFS_MEMORY);
-  
+
   //EspFsInitResult res = espFsInit(&_binary_espfs_img_start);
   //os_printf("espFsInit %s\n", res?"ERR":"ok");
   // mount the http handlers
   httpdInit(builtInUrls, 80);
   WEB_Init();
-  
+
   // init the wifi-serial transparent bridge (port 23)
   serbridgeInit(23, 2323);
   uart_add_recv_cb(&serbridgeUartCb);