diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..4a67053
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "lib/mruby/mruby"]
+	path = lib/mruby/mruby
+	url = https://github.com/mruby/mruby.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1bf177c..af242b5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,6 +16,7 @@ set(TARGET_LDSCRIPT_RAM   "${CMAKE_SOURCE_DIR}/STM32H750VBTx_RAM.ld")
 
 # Copy them from Makefile
 set(TARGET_C_SOURCES
+    "Core/Src/libc-hooks.c"
     "Core/Src/main.c"
     "Core/Src/stm32h7xx_it.c"
     "Core/Src/stm32h7xx_hal_msp.c"
@@ -76,14 +77,17 @@ set(TARGET_C_INCLUDES
     "Drivers/STM32H7xx_HAL_Driver/Inc/Legacy"
     "Drivers/CMSIS/Device/ST/STM32H7xx/Include"
     "Drivers/CMSIS/Include"
+    "lib/mruby/mruby/include"
 )
 
 # Shared libraries linked with application
 set(TARGET_LIBS
+    "mruby"
 )
 
 # Shared library and linker script search paths
 set(TARGET_LIB_DIRECTORIES
+    "lib/mruby/mruby/build/STM32H750/lib"
 )
 
 # Device specific settings, goes to CFLAGS and LDFLAGS
diff --git a/Core/Src/libc-hooks.c b/Core/Src/libc-hooks.c
new file mode 100644
index 0000000..1538b05
--- /dev/null
+++ b/Core/Src/libc-hooks.c
@@ -0,0 +1,67 @@
+#include <stdio.h>
+#include <sys/stat.h>
+
+#include "stm32h7xx_hal.h"
+
+extern UART_HandleTypeDef huart1;
+
+/* Place heap inside DTCMRAM. */
+#define HEAP_BASE 0x20000000
+#define HEAP_SIZE 0x00020000
+
+size_t s_heap_sz = 0;
+
+int _getpid(void) {
+    return 0;
+}
+
+int _kill(int i, int j) {
+    return 0;
+}
+
+int _read(int fd, char *buf, int nbytes) {
+    return 0;
+}
+
+int _write(int fd, const void *buf, int nbytes) {
+    HAL_StatusTypeDef res;
+    res = HAL_UART_Transmit(&huart1, (uint8_t *)buf, nbytes, 1000);
+
+    if(res != HAL_OK) {
+        return 0;
+    }
+
+    return nbytes;
+}
+
+int _close(int file) {
+    return -1;
+}
+
+int _isatty(int file) {
+    return file <= 2;
+}
+
+int _fstat(int file, struct stat *st) {
+    st->st_mode = S_IFCHR;
+    return 0;
+}
+
+int _lseek(int file, int ptr, int dir){
+	return 0;
+}
+
+void *_sbrk(intptr_t count) {
+    void *ret, *ptr;
+
+    ptr = ((char *)HEAP_BASE) + s_heap_sz;
+    if(s_heap_sz + count < HEAP_SIZE) {
+        s_heap_sz += count;
+        ret = ptr;
+    }
+    else {
+        ret = (void *)-1;
+    }
+
+    return ret;
+}
\ No newline at end of file
diff --git a/Core/Src/main.c b/Core/Src/main.c
index 0e8d420..2948810 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -22,6 +22,11 @@
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
 
+#include <malloc.h>
+
+#include "mruby.h"
+#include "mruby/compile.h"
+
 /* USER CODE END Includes */
 
 /* Private typedef -----------------------------------------------------------*/
@@ -57,6 +62,11 @@ static void MX_USART1_UART_Init(void);
 /* Private user code ---------------------------------------------------------*/
 /* USER CODE BEGIN 0 */
 
+static void report_heap(void) {
+  struct mallinfo mi = mallinfo();
+  printf("\r\nHeap usage: %d bytes.\r\n", mi.uordblks);
+}
+
 /* USER CODE END 0 */
 
 /**
@@ -90,6 +100,33 @@ int main(void)
   MX_USART1_UART_Init();
   /* USER CODE BEGIN 2 */
 
+  char *script_str =
+      "puts \"mruby v#{RUBY_VERSION} on STM32!\\r\\n\"\n"
+      "i = 0\n"
+      "loop do\n"
+      "  puts \"Hello world ##{i}\\r\\n\"\n"
+      "  i += 1\n"
+      "  Sleep.sleep_ms(1000)\n"
+      "end\n";
+
+  printf("\r\nInitializing MRB core.\r\n");
+
+  report_heap();
+
+  mrb_state *mrb = mrb_open();
+
+  printf("MRB: %p\r\n", mrb);
+
+  mrb_load_string(mrb, script_str);
+
+  report_heap();
+
+  mrb_close(mrb);
+
+  printf("Closed MRB core.\r\n");
+
+  report_heap();
+
   /* USER CODE END 2 */
 
   /* Infinite loop */
diff --git a/lib/mruby/build_config.rb b/lib/mruby/build_config.rb
new file mode 100644
index 0000000..0295fd4
--- /dev/null
+++ b/lib/mruby/build_config.rb
@@ -0,0 +1,64 @@
+MRuby::CrossBuild.new("STM32H750") do |conf|
+    toolchain :gcc
+  
+    # Linux
+    BIN_PATH = "/usr/bin"
+  
+    conf.cc do |cc|
+      cc.command = "#{BIN_PATH}/arm-none-eabi-gcc"
+      cc.flags = "-Wall -g -O2 -flto -mcpu=cortex-m7 -mfloat-abi=hard -mfpu=fpv5-d16"
+      cc.compile_options = %Q[%{flags} -o "%{outfile}" -c "%{infile}"]
+  
+      #configuration for low memory environment
+      #cc.defines << %w(MRB_USE_FLOAT32)
+      cc.defines << %w(MRB_HEAP_PAGE_SIZE=64)
+      cc.defines << %w(KHASH_DEFAULT_SIZE=8)
+      cc.defines << %w(MRB_GC_STRESS)
+      #cc.defines << %w(MRB_NO_STDIO) #if you don't need stdio.
+      #cc.defines << %w(POOL_PAGE_SIZE=1000) #effective only for use with mruby-eval
+    end
+  
+    conf.cxx do |cxx|
+      cxx.command = conf.cc.command.dup
+      cxx.include_paths = conf.cc.include_paths.dup
+      cxx.flags = conf.cc.flags.dup
+      cxx.defines = conf.cc.defines.dup
+      cxx.compile_options = conf.cc.compile_options.dup
+    end
+  
+    conf.linker do |linker|
+      linker.command="#{BIN_PATH}/arm-none-eabi-gcc"
+    end
+  
+    conf.archiver do |archiver|
+      archiver.command = "#{BIN_PATH}/arm-none-eabi-ar"
+      archiver.archive_options = 'rcs "%{outfile}" %{objs}'
+    end
+  
+    #no executables
+    conf.bins = []
+  
+    #do not build executable test
+    conf.build_mrbtest_lib_only
+  
+    #disable C++ exception
+    conf.disable_cxx_exception
+  
+    #gems from core
+    conf.gem :core => "mruby-compiler"
+    conf.gem :core => "mruby-enum-ext"
+    conf.gem :core => "mruby-math"
+    conf.gem :core => "mruby-numeric-ext"
+    conf.gem :core => "mruby-print"
+    conf.gem :core => "mruby-sprintf"
+
+    #light-weight regular expression
+    #conf.gem :github => "masamitsu-murase/mruby-hs-regexp", :branch => "master"
+  
+    #Arduino API
+    #conf.gem :github =>"kyab/mruby-arduino", :branch => "master"
+  
+    conf.gem 'gems/sleep'
+
+  end
+  
\ No newline at end of file
diff --git a/lib/mruby/build_mruby.sh b/lib/mruby/build_mruby.sh
new file mode 100644
index 0000000..230abdf
--- /dev/null
+++ b/lib/mruby/build_mruby.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+cd mruby
+
+rake MRUBY_CONFIG=../build_config.rb
\ No newline at end of file
diff --git a/lib/mruby/gems/sleep/mrbgem.rake b/lib/mruby/gems/sleep/mrbgem.rake
new file mode 100644
index 0000000..49afd48
--- /dev/null
+++ b/lib/mruby/gems/sleep/mrbgem.rake
@@ -0,0 +1,36 @@
+PROJ_ROOT="../../.."
+
+
+MRuby::Gem::Specification.new('sleep') do |spec|
+    spec.license = 'MIT'
+    spec.author  = 'imi415'
+
+    spec.cc.include_paths << "#{PROJ_ROOT}/Drivers/STM32H7xx_HAL_Driver/Inc"
+    spec.cc.include_paths << "#{PROJ_ROOT}/Core/Inc"
+    spec.cc.include_paths << "#{PROJ_ROOT}/Drivers/STM32H7xx_HAL_Driver/Inc/Legacy"
+    spec.cc.include_paths << "#{PROJ_ROOT}/Drivers/CMSIS/Device/ST/STM32H7xx/Include"
+    spec.cc.include_paths << "#{PROJ_ROOT}/Drivers/CMSIS/Include"
+
+    spec.cc.defines << "STM32H750xx"
+    spec.cc.defines << "USE_HAL_DRIVER"
+
+  
+    # Add compile flags
+    # spec.cc.flags << '-g'
+  
+    # Add cflags to all
+    # spec.mruby.cc.flags << '-g'
+  
+    # Add libraries
+    # spec.linker.libraries << 'external_lib'
+  
+    # Default build files
+    # spec.rbfiles = Dir.glob("#{dir}/mrblib/*.rb")
+    # spec.objs = Dir.glob("#{dir}/src/*.{c,cpp,m,asm,S}").map { |f| objfile(f.relative_path_from(dir).pathmap("#{build_dir}/%X")) }
+    # spec.test_rbfiles = Dir.glob("#{dir}/test/*.rb")
+    # spec.test_objs = Dir.glob("#{dir}/test/*.{c,cpp,m,asm,S}").map { |f| objfile(f.relative_path_from(dir).pathmap("#{build_dir}/%X")) }
+    # spec.test_preload = 'test/assert.rb'
+  
+    # Values accessible as TEST_ARGS inside test scripts
+    # spec.test_args = {'tmp_dir' => Dir::tmpdir}
+  end
\ No newline at end of file
diff --git a/lib/mruby/gems/sleep/src/sleep.c b/lib/mruby/gems/sleep/src/sleep.c
new file mode 100644
index 0000000..312d320
--- /dev/null
+++ b/lib/mruby/gems/sleep/src/sleep.c
@@ -0,0 +1,32 @@
+#include <mruby.h>
+#include <mruby/string.h>
+
+#include "stm32h7xx_hal.h"
+
+static mrb_value sleep_ms_c_method(mrb_state* mrb, mrb_value self) {
+    mrb_value* argv;
+    mrb_int    argc;
+    mrb_get_args(mrb, "*", &argv, &argc);
+
+    int iargc = (int)argc;
+
+    if (iargc == 0 || iargc >= 2) {
+        mrb_raise(mrb, E_ARGUMENT_ERROR, "wrong number of arguments");
+    }
+
+    if (mrb_fixnum_p(argv[0]) && mrb_fixnum(argv[0]) >= 0) {
+        HAL_Delay(mrb_fixnum(argv[0]));
+    } else {
+        mrb_raise(mrb, E_ARGUMENT_ERROR, "time interval must be positive integer");
+    }
+
+    return self;
+}
+
+void mrb_sleep_gem_init(mrb_state* mrb) {
+    struct RClass* class_cextension = mrb_define_module(mrb, "Sleep");
+    mrb_define_class_method(mrb, class_cextension, "sleep_ms", sleep_ms_c_method, MRB_ARGS_REQ(1));
+}
+
+void mrb_sleep_gem_final(mrb_state* mrb) { /* finalizer */
+}
diff --git a/lib/mruby/mruby b/lib/mruby/mruby
new file mode 160000
index 0000000..69b1667
--- /dev/null
+++ b/lib/mruby/mruby
@@ -0,0 +1 @@
+Subproject commit 69b1667b5ba4d245c76d1cb99f2c813eae78b3e9