diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index b05a31a..27f10f1 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -28,8 +28,11 @@
     </configurations>
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="56631632-52f0-4e39-b905-89e46eb6e768" name="Changes" comment="">
-      <change afterPath="$PROJECT_DIR$/.gitignore" afterDir="false" />
+    <list default="true" id="56631632-52f0-4e39-b905-89e46eb6e768" name="Changes" comment="initial commit: oled, rc522, exti">
+      <change afterPath="$PROJECT_DIR$/Core/Inc/retarget.h" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/Core/Src/retarget.c" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/Core/Src/main.c" beforeDir="false" afterPath="$PROJECT_DIR$/Core/Src/main.c" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -62,14 +65,17 @@
   </component>
   <component name="PropertiesComponent"><![CDATA[{
   "keyToString": {
+    "ASKED_SHARE_PROJECT_CONFIGURATION_FILES": "true",
     "CMake Application.IntelliChargingPile.elf.executor": "Run",
     "OpenOCD Download & Run.IntelliChargingPile.elf.executor": "Run",
     "OpenOCD Download & Run.OCD IntelliChargingPile.executor": "Run",
     "RunOnceActivity.RadMigrateCodeStyle": "true",
     "RunOnceActivity.ShowReadmeOnStart": "true",
     "RunOnceActivity.cidr.known.project.marker": "true",
+    "RunOnceActivity.git.unshallow": "true",
     "RunOnceActivity.readMode.enableVisualFormatting": "true",
     "RunOnceActivity.west.config.association.type.startup.service": "true",
+    "SHARE_PROJECT_CONFIGURATION_FILES": "true",
     "cf.first.check.clang-format": "false",
     "cidr.known.project.marker": "true",
     "git-widget-placeholder": "main",
@@ -89,12 +95,12 @@
     </key>
   </component>
   <component name="RunManager" selected="OpenOCD Download &amp; Run.OCD IntelliChargingPile">
-    <configuration name="IntelliChargingPile.elf" type="CMakeRunConfiguration" factoryName="Application" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true" PROJECT_NAME="IntelliChargingPile" TARGET_NAME="IntelliChargingPile.elf" CONFIG_NAME="Debug" RUN_TARGET_PROJECT_NAME="IntelliChargingPile" RUN_TARGET_NAME="IntelliChargingPile.elf">
+    <configuration default="true" type="CLionExternalRunConfiguration" factoryName="Application" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true">
       <method v="2">
-        <option name="com.jetbrains.cidr.execution.CidrBuildBeforeRunTaskProvider$BuildBeforeRunTask" enabled="true" />
+        <option name="CLION.EXTERNAL.BUILD" enabled="true" />
       </method>
     </configuration>
-    <configuration default="true" type="CMakeRunConfiguration" factoryName="Application" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true">
+    <configuration name="IntelliChargingPile.elf" type="CMakeRunConfiguration" factoryName="Application" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true" PROJECT_NAME="IntelliChargingPile" TARGET_NAME="IntelliChargingPile.elf" CONFIG_NAME="Debug" RUN_TARGET_PROJECT_NAME="IntelliChargingPile" RUN_TARGET_NAME="IntelliChargingPile.elf">
       <method v="2">
         <option name="com.jetbrains.cidr.execution.CidrBuildBeforeRunTaskProvider$BuildBeforeRunTask" enabled="true" />
       </method>
@@ -122,8 +128,18 @@
       <updated>1742375125098</updated>
       <workItem from="1742375147816" duration="297000" />
       <workItem from="1742375453292" duration="8414000" />
-      <workItem from="1742385111843" duration="9863000" />
+      <workItem from="1742385111843" duration="9995000" />
+      <workItem from="1742408425253" duration="828000" />
     </task>
+    <task id="LOCAL-00001" summary="initial commit: oled, rc522, exti">
+      <option name="closed" value="true" />
+      <created>1742407507479</created>
+      <option name="number" value="00001" />
+      <option name="presentableId" value="LOCAL-00001" />
+      <option name="project" value="LOCAL" />
+      <updated>1742407507479</updated>
+    </task>
+    <option name="localTasksCounter" value="2" />
     <servers />
   </component>
   <component name="TypeScriptGeneratedFilesManager">
@@ -134,4 +150,8 @@
     <isAutomaticFoundErrors value="true" />
     <isAutomaticReloadCMake value="true" />
   </component>
+  <component name="VcsManagerConfiguration">
+    <MESSAGE value="initial commit: oled, rc522, exti" />
+    <option name="LAST_COMMIT_MESSAGE" value="initial commit: oled, rc522, exti" />
+  </component>
 </project>
\ No newline at end of file
diff --git a/Core/Inc/retarget.h b/Core/Inc/retarget.h
new file mode 100644
index 0000000..1892363
--- /dev/null
+++ b/Core/Inc/retarget.h
@@ -0,0 +1,22 @@
+#ifndef _RETARGET_H__
+#define _RETARGET_H__
+
+#include "stm32f1xx_hal.h"
+#include <sys/stat.h>
+#include <stdio.h>
+
+void RetargetInit(UART_HandleTypeDef *huart);
+
+int _isatty(int fd);
+
+int _write(int fd, char *ptr, int len);
+
+int _close(int fd);
+
+int _lseek(int fd, int ptr, int dir);
+
+int _read(int fd, char *ptr, int len);
+
+int _fstat(int fd, struct stat *st);
+
+#endif //#ifndef _RETARGET_H__
\ No newline at end of file
diff --git a/Core/Src/main.c b/Core/Src/main.c
index 4b22c79..0748fa1 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -27,6 +27,7 @@
 /* USER CODE BEGIN Includes */
 #include <stdio.h>
 
+#include "retarget.h"
 #include "oled.h"
 #include "rc522.h"
 /* USER CODE END Includes */
@@ -119,13 +120,19 @@ int main(void)
   MX_USART1_UART_Init();
   MX_SPI1_Init();
   /* USER CODE BEGIN 2 */
+  // Retarget uart
+  RetargetInit(&huart1);
+
+  // Init RC522
   MFRC_Init();
   PCD_Reset();
 
+  // Init OLED
   OLED_Init();
   OLED_Clear();
 
   OLED_ShowString(0,0,"Card scan...",12);
+  printf("startup\n");
   /* USER CODE END 2 */
 
   /* Infinite loop */
diff --git a/Core/Src/retarget.c b/Core/Src/retarget.c
new file mode 100644
index 0000000..4a031d3
--- /dev/null
+++ b/Core/Src/retarget.c
@@ -0,0 +1,98 @@
+#include <_ansi.h>
+#include <_syslist.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <sys/times.h>
+#include <retarget.h>
+#include <stdint.h>
+
+#if !defined(OS_USE_SEMIHOSTING)
+
+#define STDIN_FILENO  0
+#define STDOUT_FILENO 1
+#define STDERR_FILENO 2
+
+UART_HandleTypeDef *gHuart;
+
+void RetargetInit(UART_HandleTypeDef *huart)
+{
+    gHuart = huart;
+    
+        /* Disable I/O buffering for STDOUT stream, so that
+         * chars are sent out as soon as they are printed. */
+        setvbuf(stdout, NULL, _IONBF, 0);
+}
+
+int _isatty(int fd)
+{
+    if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
+        return 1;
+    
+        errno = EBADF;
+    return 0;
+}
+
+int _write(int fd, char *ptr, int len)
+{
+    HAL_StatusTypeDef hstatus;
+    
+        if (fd == STDOUT_FILENO || fd == STDERR_FILENO)
+        {
+            hstatus = HAL_UART_Transmit(gHuart, (uint8_t *) ptr, len, HAL_MAX_DELAY);
+            if (hstatus == HAL_OK)
+                return len;
+            else
+                return EIO;
+        }
+    errno = EBADF;
+    return -1;
+}
+
+int _close(int fd)
+{
+    if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
+        return 0;
+    
+        errno = EBADF;
+    return -1;
+}
+
+int _lseek(int fd, int ptr, int dir)
+{
+    (void) fd;
+    (void) ptr;
+    (void) dir;
+    
+        errno = EBADF;
+    return -1;
+}
+
+int _read(int fd, char *ptr, int len)
+{
+    HAL_StatusTypeDef hstatus;
+    
+        if (fd == STDIN_FILENO)
+        {
+            hstatus = HAL_UART_Receive(gHuart, (uint8_t *) ptr, 1, HAL_MAX_DELAY);
+            if (hstatus == HAL_OK)
+                return 1;
+            else
+                return EIO;
+        }
+    errno = EBADF;
+    return -1;
+}
+
+int _fstat(int fd, struct stat *st)
+{
+    if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
+    {
+        st->st_mode = S_IFCHR;
+        return 0;
+    }
+    
+        errno = EBADF;
+    return 0;
+}
+
+#endif //#if !defined(OS_USE_SEMIHOSTING)
\ No newline at end of file
diff --git a/Core/Src/syscalls.c b/Core/Src/syscalls.c
index 8884b5a..b749d9d 100644
--- a/Core/Src/syscalls.c
+++ b/Core/Src/syscalls.c
@@ -89,33 +89,33 @@ __attribute__((weak)) int _write(int file, char *ptr, int len)
   return len;
 }
 
-int _close(int file)
-{
-  (void)file;
-  return -1;
-}
-
-
-int _fstat(int file, struct stat *st)
-{
-  (void)file;
-  st->st_mode = S_IFCHR;
-  return 0;
-}
-
-int _isatty(int file)
-{
-  (void)file;
-  return 1;
-}
-
-int _lseek(int file, int ptr, int dir)
-{
-  (void)file;
-  (void)ptr;
-  (void)dir;
-  return 0;
-}
+// int _close(int file)
+// {
+//   (void)file;
+//   return -1;
+// }
+//
+//
+// int _fstat(int file, struct stat *st)
+// {
+//   (void)file;
+//   st->st_mode = S_IFCHR;
+//   return 0;
+// }
+//
+// int _isatty(int file)
+// {
+//   (void)file;
+//   return 1;
+// }
+//
+// int _lseek(int file, int ptr, int dir)
+// {
+//   (void)file;
+//   (void)ptr;
+//   (void)dir;
+//   return 0;
+// }
 
 int _open(char *path, int flags, ...)
 {