diff --git a/lib/bsp/entry_user.c b/lib/bsp/entry_user.c
index 4902fb3..3fefb2f 100644
--- a/lib/bsp/entry_user.c
+++ b/lib/bsp/entry_user.c
@@ -73,13 +73,9 @@ void _init_bsp(int core_id, int number_of_cores)
         /* Initialize bss data to 0 */
         init_bss();
         /* Init UART */
-        uart_init(UART_DEVICE_3);
-        uart_configure(UART_DEVICE_3, 115200, 8, UART_STOP_1, UART_PARITY_NONE);
-        uart_set_receive_trigger(UART_DEVICE_3, UART_RECEIVE_FIFO_1);
         fpioa_set_function(4, FUNC_UART3_RX);
         fpioa_set_function(5, FUNC_UART3_TX);
-        sys_register_getchar(uart3_getchar);
-        sys_register_putchar(uart3_putchar);
+        uart_debug_init(UART_DEVICE_3);
         /* Init FPIOA */
         fpioa_init();
         /* Register finalization function */
diff --git a/lib/bsp/include/bsp.h b/lib/bsp/include/bsp.h
index deecc67..2c384eb 100644
--- a/lib/bsp/include/bsp.h
+++ b/lib/bsp/include/bsp.h
@@ -4,4 +4,6 @@
 #include "entry.h"
 #include "sleep.h"
 #include "encoding.h"
+#include "syscalls.h"
+#include "printf.h"
 #endif
\ No newline at end of file
diff --git a/lib/bsp/include/syscalls.h b/lib/bsp/include/syscalls.h
index 50c4c93..496509e 100644
--- a/lib/bsp/include/syscalls.h
+++ b/lib/bsp/include/syscalls.h
@@ -76,14 +76,11 @@ void sys_stdin_flush(void);
 
 void __attribute__((noreturn)) sys_exit(int code);
 
-void setStats(int enable);
-
-#undef putchar
-int putchar(int ch);
-void printstr(const char *s);
-
-void printhex(uint64_t x);
-
+/**
+ * @brief       Get free memory
+ *
+ * @return      The size of free memory
+ */
 size_t get_free_heap_size(void);
 
 #ifdef __cplusplus
diff --git a/lib/drivers/include/uart.h b/lib/drivers/include/uart.h
index 4a13cc0..5c4e21f 100644
--- a/lib/drivers/include/uart.h
+++ b/lib/drivers/include/uart.h
@@ -470,64 +470,12 @@ void uart_set_tat(uart_device_number_t uart_channel, uart_tat_mode_t tat_mode, s
 void uart_set_det(uart_device_number_t uart_channel, uart_det_mode_t det_mode, size_t time);
 
 /**
- * @brief       Put a char to UART1
+ * @brief       Set the default debug serial port
  *
- * @param[in]   c       The char to put
+ * @param[in]   uart_channel        Uart index
  *
- * @return      result
- *     - Byte   On success, returns the written character.
- *     - EOF    On failure, returns EOF and sets the error indicator (see ferror()) on stdout.
  */
-int uart1_putchar(char c);
-
-/**
- * @brief       Get a byte from UART1
- *
- * @return      byte as int type from UART
- *     - Byte   The character read as an unsigned char cast to an int
- *     - EOF    EOF on end of file or error, no enough byte to read
- */
-int uart1_getchar(void);
-
-/**
- * @brief       Put a char to UART2
- *
- * @param[in]   c       The char to put
- *
- * @return      result
- *     - Byte   On success, returns the written character.
- *     - EOF    On failure, returns EOF and sets the error indicator (see ferror()) on stdout.
- */
-int uart2_putchar(char c);
-
-/**
- * @brief       Get a byte from UART2
- *
- * @return      byte as int type from UART
- *     - Byte   The character read as an unsigned char cast to an int
- *     - EOF    EOF on end of file or error, no enough byte to read
- */
-int uart2_getchar(void);
-
-/**
- * @brief       Put a char to UART3
- *
- * @param[in]   c       The char to put
- *
- * @return      result
- *     - Byte   On success, returns the written character.
- *     - EOF    On failure, returns EOF and sets the error indicator (see ferror()) on stdout.
- */
-int uart3_putchar(char c);
-
-/**
- * @brief       Get a byte from UART3
- *
- * @return      byte as int type from UART
- *     - Byte   The character read as an unsigned char cast to an int
- *     - EOF    EOF on end of file or error, no enough byte to read
- */
-int uart3_getchar(void);
+void uart_debug_init(uart_device_number_t uart_channel);
 
 #ifdef __cplusplus
 }
diff --git a/lib/drivers/sysctl.c b/lib/drivers/sysctl.c
index 1d719ee..26c5c3b 100644
--- a/lib/drivers/sysctl.c
+++ b/lib/drivers/sysctl.c
@@ -20,6 +20,7 @@
 #include "string.h"
 #include "encoding.h"
 #include "bsp.h"
+#include "uart.h"
 
 #define SYSCTRL_CLOCK_FREQ_IN0 (26000000UL)
 
@@ -1790,8 +1791,10 @@ uint32_t sysctl_pll_set_freq(sysctl_pll_t pll, uint32_t pll_freq)
 
     /* 9. Change CPU CLK to PLL */
     if(pll == SYSCTL_PLL0)
+    {
         sysctl_clock_set_clock_select(SYSCTL_CLOCK_SELECT_ACLK, SYSCTL_SOURCE_PLL0);
-
+        uart_debug_init(-1);
+    }
     return result;
 }
 
diff --git a/lib/drivers/uart.c b/lib/drivers/uart.c
index 953b145..ceb21c0 100644
--- a/lib/drivers/uart.c
+++ b/lib/drivers/uart.c
@@ -19,6 +19,7 @@
 #include "uart.h"
 #include "utils.h"
 #include "atomic.h"
+#include "syscalls.h"
 
 #define __UART_BRATE_CONST  16
 
@@ -95,7 +96,9 @@ static int uart_irq_callback(void *param)
     return 0;
 }
 
-int uart_channel_putc(char c, uart_device_number_t channel)
+static uart_device_number_t s_uart_debug_channel = UART_DEVICE_3;
+
+static int uart_channel_putc(char c, uart_device_number_t channel)
 {
     while (uart[channel]->LSR & (1u << 5))
         continue;
@@ -103,7 +106,7 @@ int uart_channel_putc(char c, uart_device_number_t channel)
     return c & 0xff;
 }
 
-int uart_channel_getc(uart_device_number_t channel)
+static int uart_channel_getc(uart_device_number_t channel)
 {
     /* If received empty */
     if (!(uart[channel]->LSR & 1))
@@ -112,34 +115,39 @@ int uart_channel_getc(uart_device_number_t channel)
         return (char)(uart[channel]->RBR & 0xff);
 }
 
-int uart1_putchar(char c)
+static int uart_debug_putchar(char c)
 {
-    return uart_channel_putc(c, UART_DEVICE_1);
+    return uart_channel_putc(c, s_uart_debug_channel);
 }
 
-int uart1_getchar(void)
+static int uart_debug_getchar(void)
 {
-    return uart_channel_getc(UART_DEVICE_1);
+    return uart_channel_getc(s_uart_debug_channel);
 }
 
-int uart2_putchar(char c)
+void uart_debug_init(uart_device_number_t uart_channel)
 {
-    return uart_channel_putc(c, UART_DEVICE_2);
-}
-
-int uart2_getchar(void)
-{
-    return uart_channel_getc(UART_DEVICE_2);
-}
-
-int uart3_putchar(char c)
-{
-    return uart_channel_putc(c, UART_DEVICE_3);
-}
-
-int uart3_getchar(void)
-{
-    return uart_channel_getc(UART_DEVICE_3);
+    volatile bool v_uart_reset_flag = false;
+    if(uart_channel >= UART_DEVICE_1 && uart_channel <= UART_DEVICE_3)
+    {
+        s_uart_debug_channel = uart_channel;
+        v_uart_reset_flag = true;
+    }
+    uart_init(s_uart_debug_channel);
+    uart_configure(s_uart_debug_channel, 115200, 8, UART_STOP_1, UART_PARITY_NONE);
+    uart_set_receive_trigger(s_uart_debug_channel, UART_RECEIVE_FIFO_1);
+    if(v_uart_reset_flag)
+    {
+        sys_register_getchar(uart_debug_getchar);
+        sys_register_putchar(uart_debug_putchar);
+    }
+    else
+    {
+        if(sys_getchar == NULL)
+            sys_register_getchar(uart_debug_getchar);
+        if(sys_putchar == NULL)
+            sys_register_putchar(uart_debug_putchar);
+    }
 }
 
 static int uart_dma_callback(void *ctx)
diff --git a/src/hello_world/main.c b/src/hello_world/main.c
index 8edd386..59655cc 100644
--- a/src/hello_world/main.c
+++ b/src/hello_world/main.c
@@ -12,9 +12,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#include <stdio.h>
-#include <uart.h>
-#include "bsp.h"
+#include <bsp.h>
+#include <sysctl.h>
 
 int core1_function(void *ctx)
 {
@@ -23,9 +22,9 @@ int core1_function(void *ctx)
     while(1);
 }
 
-
-int main()
+int main(void)
 {
+    sysctl_pll_set_freq(SYSCTL_PLL0, 800000000);
     uint64_t core = current_coreid();
     int data;
     printf("Core %ld Hello world\n", core);
@@ -35,7 +34,8 @@ int main()
     sys_stdin_flush();
 
     scanf("%d", &data);
-    printf("Data is %d\n", data);
+    printf("\nData is %d\n", data);
     while(1)
         continue;
+    return 0;
 }