diff --git a/CMakeLists.txt b/CMakeLists.txt
index 15c52172..5feaf157 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,13 +10,15 @@ add_definitions(
   -DMRBC_REQUIRE_32BIT_ALIGNMENT
   -DMAX_REGS_SIZE=256
   -DMAX_VM_COUNT=255
-  -DMAX_SYMBOLS_COUNT=1000
+  -DMAX_SYMBOLS_COUNT=2000
   -DMRBC_CONVERT_CRLF
   -DMRBC_USE_MATH
   -DPICORBC_PTR_SIZE=4
 )
-if(PRK_NO_MSC)
-  add_definitions(-DPRK_NO_MSC)
+if(PICORUBY_NO_MSC)
+  add_definitions(-DPICORUBY_NO_MSC)
+else()
+  add_definitions(-DPICORUBY_MSC_FLASH)
 endif()
 
 #####################################################
@@ -30,7 +32,7 @@ set (PRK_BUILDDATE ${CMAKE_BUILDDATE})
 set (PRK_REVISION  ${CMAKE_REVISION})
 configure_file ("${CMAKE_SOURCE_DIR}/include/version.h.in" "${CMAKE_SOURCE_DIR}/include/version.h")
 
-if(PRK_NO_MSC)
+if(PICORUBY_NO_MSC)
   project("prk_firmware-${PRK_VERSION}-${PRK_BUILDDATE}-no_msc")
 else()
   project("prk_firmware-${PRK_VERSION}-${PRK_BUILDDATE}-${PRK_REVISION}")
@@ -43,6 +45,7 @@ file(GLOB SRCS src/*.c)
 add_executable(${PROJECT_NAME}
   ${SRCS}
   ${CMAKE_SOURCE_DIR}/lib/picoruby/mrbgems/picoruby-filesystem-fat/ports/rp2040/flash_disk.c
+  ${CMAKE_SOURCE_DIR}/lib/picoruby/mrbgems/picoruby-filesystem-fat/ports/rp2040/msc_disk.c
   ${CMAKE_SOURCE_DIR}/lib/picoruby/mrbgems/picoruby-gpio/ports/rp2040/gpio.c
   ${CMAKE_SOURCE_DIR}/lib/picoruby/mrbgems/picoruby-i2c/ports/rp2040/i2c.c
   ${CMAKE_SOURCE_DIR}/lib/picoruby/mrbgems/picoruby-spi/ports/rp2040/spi.c
@@ -59,7 +62,7 @@ set(RBC ${CMAKE_CURRENT_SOURCE_DIR}/lib/picoruby/bin/picorbc)
 
 # Ruby
 
-if(PRK_NO_MSC)
+if(PICORUBY_NO_MSC)
   add_custom_target(keymap
     COMMAND ${RBC} -Bkeymap -o ./keymap.c ../keymap.rb
     WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
@@ -96,7 +99,7 @@ add_dependencies(${PROJECT_NAME}
   ${RUBY_TASK_FILES}
 )
 
-if(PRK_NO_MSC)
+if(PICORUBY_NO_MSC)
   add_dependencies(${PROJECT_NAME}
     keymap
   )
diff --git a/Gemfile.lock b/Gemfile.lock
index ae4ada81..1bf1e358 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -6,16 +6,16 @@ GEM
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
       tzinfo (~> 2.0)
-    concurrent-ruby (1.2.0)
+    concurrent-ruby (1.2.2)
     i18n (1.12.0)
       concurrent-ruby (~> 1.0)
-    minitest (5.17.0)
-    mrubyc-test (0.9.1)
+    minitest (5.18.0)
+    mrubyc-test (0.9.2)
       activesupport (~> 7.0)
       rufo (~> 0.12)
       thor (~> 1.2)
     rake (13.0.6)
-    rufo (0.14.0)
+    rufo (0.15.1)
     thor (1.2.1)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
diff --git a/Rakefile b/Rakefile
index 078529fa..e04a095b 100644
--- a/Rakefile
+++ b/Rakefile
@@ -26,7 +26,7 @@ end
 task :libmruby_no_msc => "lib/picoruby" do
   FileUtils.cd "lib/picoruby" do
     sh "rake test"
-    sh "CFLAGS='-DPRK_NO_MSC=1' MRUBY_CONFIG=#{MRUBY_CONFIG} rake"
+    sh "CFLAGS='-DPICORUBY_NO_MSC=1' MRUBY_CONFIG=#{MRUBY_CONFIG} rake"
   end
 end
 
@@ -81,8 +81,8 @@ task :build_with_keymap, ['keyboard_name'] => [:libmruby_no_msc, :test] do |_t,
   end
   dir = "keyboards/#{args.keyboard_name}"
   FileUtils.mkdir_p "#{dir}/build"
-  #sh "cmake -DPRK_NO_MSC=1 -DCMAKE_BUILD_TYPE=Debug -B #{dir}/build"
-  sh "#{mruby_config} cmake -DPRK_NO_MSC=1 -B #{dir}/build"
+  #sh "cmake -DPICORUBY_NO_MSC=1 -DCMAKE_BUILD_TYPE=Debug -B #{dir}/build"
+  sh "#{mruby_config} cmake -DPICORUBY_NO_MSC=1 -B #{dir}/build"
   sh "cmake --build #{dir}/build"
 end
 
@@ -100,7 +100,7 @@ task :test => %i(mrubyc_test)
 
 desc "run unit test for ruby program"
 task :mrubyc_test => :setup_test do
-  sh %q(CFLAGS=-DMAX_SYMBOLS_COUNT=1000 MRUBYCFILE=test/Mrubycfile bundle exec mrubyc-test)
+  sh %q(MRUBYCFILE=test/Mrubycfile bundle exec mrubyc-test)
 end
 
 task :setup_test do
diff --git a/lib/picoruby b/lib/picoruby
index 9c06b76d..cc253a6e 160000
--- a/lib/picoruby
+++ b/lib/picoruby
@@ -1 +1 @@
-Subproject commit 9c06b76dbcc1dd09ef36b58cdfedfb5de57cadad
+Subproject commit cc253a6e09199e34fdca7dd54899825fe4203c2a
diff --git a/src/keyboard.c b/src/keyboard.c
index 5ff198a8..fba7ea52 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -241,7 +241,7 @@ Keyboard_init_sub(mrbc_class *mrbc_class_Keyboard)
   mrbc_define_method(0, mrbc_class_Keyboard, "uart_anchor", c_Keyboard_uart_anchor);
   mrbc_define_method(0, mrbc_class_Keyboard, "autoreload_ready?", c_autoreload_ready_q);
   mrbc_define_method(0, mrbc_class_Keyboard, "autoreload_off", c_autoreload_off);
-#ifdef PRK_NO_MSC
+#ifdef PICORUBY_NO_MSC
   autoreload_state = AUTORELOAD_NONE;
 #else
   autoreload_state = AUTORELOAD_READY;
diff --git a/src/main.c b/src/main.c
index e78e51be..04c96ad4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -27,7 +27,7 @@
 /* tasks */
 #include "../build/mrb/usb_task.c"
 
-#ifdef PRK_NO_MSC
+#ifdef PICORUBY_NO_MSC
 #include <keymap.c>
 #endif
 
@@ -41,13 +41,20 @@ int loglevel = LOGLEVEL_WARN;
 
 int autoreload_state; /* from keyboard.h */
 
-#ifndef PRK_NO_MSC
+#ifndef PICORUBY_NO_MSC
 
 #ifndef NODE_BOX_SIZE
 #define NODE_BOX_SIZE 50
 #endif
 
-#endif /* PRK_NO_MSC */
+void
+tud_msc_write10_complete_cb(uint8_t lun)
+{
+  (void)lun;
+  autoreload_state = AUTORELOAD_READY;
+}
+
+#endif /* PICORUBY_NO_MSC */
 
 static void
 prk_init_picoruby(void)
@@ -55,8 +62,8 @@ prk_init_picoruby(void)
   /* CONST */
   mrbc_sym sym_id = mrbc_str_to_symid("SIZEOF_POINTER");
   mrbc_set_const(sym_id, &mrbc_integer_value(PICORBC_PTR_SIZE));
-  sym_id = mrbc_str_to_symid("PRK_NO_MSC");
-#ifdef PRK_NO_MSC
+  sym_id = mrbc_str_to_symid("PICORUBY_NO_MSC");
+#ifdef PICORUBY_NO_MSC
   mrbc_set_const(sym_id, &mrbc_true_value());
 #else
   mrbc_set_const(sym_id, &mrbc_false_value());
@@ -87,7 +94,7 @@ main(void)
   tusb_init();
   /* Tasks */
   mrbc_create_task(usb_task, 0);
-#ifdef PRK_NO_MSC
+#ifdef PICORUBY_NO_MSC
   mrbc_create_task(keymap, 0);
 #endif
   mrbc_run();
diff --git a/src/usb_descriptors.c b/src/usb_descriptors.c
index 248d9d80..3fbf3688 100644
--- a/src/usb_descriptors.c
+++ b/src/usb_descriptors.c
@@ -60,7 +60,7 @@ tud_descriptor_device_cb(void)
 // Configuration Descriptor
 //--------------------------------------------------------------------+
 
-#ifdef PRK_NO_MSC
+#ifdef PICORUBY_NO_MSC
 #define CONFIG_TOTAL_LEN    (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN + TUD_HID_INOUT_DESC_LEN + TUD_HID_DESC_LEN)
 #else
 #define CONFIG_TOTAL_LEN    (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN + TUD_MSC_DESC_LEN + TUD_HID_INOUT_DESC_LEN + TUD_HID_DESC_LEN)
@@ -131,7 +131,7 @@ enum
   ITF_NUM_CDC_DATA,
   ITF_NUM_HID,
   ITF_NUM_JOYSTICK,
-#ifndef PRK_NO_MSC
+#ifndef PICORUBY_NO_MSC
   ITF_NUM_MSC,
 #endif
   ITF_NUM_TOTAL
@@ -145,7 +145,7 @@ uint8_t const desc_fs_configuration[] =
   // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
   TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 64),
 
-#ifndef PRK_NO_MSC
+#ifndef PICORUBY_NO_MSC
   // Interface number, string index, EP Out & EP In address, EP size
   TUD_MSC_DESCRIPTOR(ITF_NUM_MSC, 5, EPNUM_MSC_OUT, EPNUM_MSC_IN, 64),
 #endif
diff --git a/test/models/gpio_c.rb b/test/models/gpio_c.rb
new file mode 100644
index 00000000..f55bee7b
--- /dev/null
+++ b/test/models/gpio_c.rb
@@ -0,0 +1,17 @@
+class GPIO
+  IN         = 0b000001
+  OUT        = 0b000010
+  HIGH_Z     = 0b000100
+  PULL_UP    = 0b001000
+  PULL_DOWN  = 0b010000
+  OPEN_DRAIN = 0b100000
+  def self._init(pin)
+  end
+  def self.set_dir_at(pin,flag)
+  end
+  def self.pull_up_at(pin)
+  end
+  def self.open_drain_at(pin)
+  end
+end
+
diff --git a/test/tests/keyboard_test.rb b/test/tests/keyboard_test.rb
index 1fd2fcde..cc6dd87b 100644
--- a/test/tests/keyboard_test.rb
+++ b/test/tests/keyboard_test.rb
@@ -1,9 +1,7 @@
 class KeyboardTest < MrubycTestCase
   # TODO: improve mock functionality of mrubyc-test
   def define_mocks
-    kbd = Keyboard.new
-    mock(kbd).gpio_init(1)
-    mock(kbd).gpio_set_dir(2)
+   # mock(GPIO)._init(1)
   end
   def setup
     @kbd = Keyboard.new