diff --git a/sdk/bsp/bsp.mk b/sdk/bsp/bsp.mk
index 03884ac..dbed548 100644
--- a/sdk/bsp/bsp.mk
+++ b/sdk/bsp/bsp.mk
@@ -23,6 +23,7 @@ C_SRCS += $(BSP_DIR)/lib/xprintf.c
 C_SRCS += $(BSP_DIR)/lib/uart.c
 C_SRCS += $(BSP_DIR)/lib/sim_ctrl.c
 C_SRCS += $(BSP_DIR)/lib/machine_timer.c
+C_SRCS += $(BSP_DIR)/lib/gpio.c
 
 LINKER_SCRIPT := $(BSP_DIR)/link.lds
 
diff --git a/sdk/bsp/include/gpio.h b/sdk/bsp/include/gpio.h
index 40533d4..c244548 100644
--- a/sdk/bsp/include/gpio.h
+++ b/sdk/bsp/include/gpio.h
@@ -7,4 +7,17 @@
 
 #define GPIO_REG(addr) (*((volatile uint32_t *)addr))
 
+
+#define GPIO0   (0)
+#define GPIO1   (1)
+
+#define GPIO_OUTPUT     (1)
+#define GPIO_INPUT      (2)
+
+void gpio_output_enable(uint8_t gpio);
+void gpio_input_enable(uint8_t gpio);
+uint8_t gpio_get_data(uint8_t gpio);
+void gpio_set_data(uint8_t gpio, uint8_t data);
+void gpio_data_toggle(uint8_t gpio);
+
 #endif
diff --git a/sdk/bsp/lib/gpio.c b/sdk/bsp/lib/gpio.c
new file mode 100644
index 0000000..3f271e0
--- /dev/null
+++ b/sdk/bsp/lib/gpio.c
@@ -0,0 +1,37 @@
+#include <stdint.h>
+
+#include "../../bsp/include/gpio.h"
+#include "../../bsp/include/utils.h"
+
+void gpio_output_enable(uint8_t gpio)
+{
+    GPIO_REG(GPIO_CTRL) &= ~(0x3 << (gpio << 1));
+    GPIO_REG(GPIO_CTRL) |= GPIO_OUTPUT << (gpio << 1);
+}
+
+void gpio_input_enable(uint8_t gpio)
+{
+    GPIO_REG(GPIO_CTRL) &= ~(0x3 << (gpio << 1));
+    GPIO_REG(GPIO_CTRL) |= GPIO_INPUT << (gpio << 1);
+}
+
+uint8_t gpio_get_data(uint8_t gpio)
+{
+    if (GPIO_REG(GPIO_DATA) & (1 << gpio))
+        return 1;
+    else
+        return 0;
+}
+
+void gpio_set_data(uint8_t gpio, uint8_t data)
+{
+    if (data)
+        GPIO_REG(GPIO_DATA) |= 1 << gpio;
+    else
+        GPIO_REG(GPIO_DATA) &= ~(1 << gpio);
+}
+
+void gpio_data_toggle(uint8_t gpio)
+{
+    GPIO_REG(GPIO_DATA) ^= 1 << gpio;
+}
diff --git a/sdk/examples/gpio/main.c b/sdk/examples/gpio/main.c
index ed61e2d..ae22c90 100644
--- a/sdk/examples/gpio/main.c
+++ b/sdk/examples/gpio/main.c
@@ -1,20 +1,20 @@
-#include <stdint.h>
-
-#include "../../bsp/include/gpio.h"
-#include "../../bsp/include/utils.h"
-
-
-int main()
-{
-    GPIO_REG(GPIO_CTRL) |= 0x1;       // gpio0输出模式
-    GPIO_REG(GPIO_CTRL) |= 0x1 << 3;  // gpio1输入模式
-
-    while (1) {
-        // 如果GPIO1输入高
-        if (GPIO_REG(GPIO_DATA) & 0x2)
-            GPIO_REG(GPIO_DATA) |= 0x1;  // GPIO0输出高
-        // 如果GPIO1输入低
-        else
-            GPIO_REG(GPIO_DATA) &= ~0x1; // GPIO0输出低
-    }
-}
+#include <stdint.h>
+
+#include "../../bsp/include/gpio.h"
+#include "../../bsp/include/utils.h"
+
+
+int main()
+{
+    gpio_output_enable(GPIO0);       // gpio0输出模式
+    gpio_input_enable(GPIO1);        // gpio1输入模式
+
+    while (1) {
+        // 如果GPIO1输入高
+        if (gpio_get_data(GPIO1))
+            gpio_set_data(GPIO0, 1);  // GPIO0输出高
+        // 如果GPIO1输入低
+        else
+            gpio_set_data(GPIO0, 0);  // GPIO0输出低
+    }
+}
diff --git a/sdk/examples/machine_timer/main.c b/sdk/examples/machine_timer/main.c
index 08f1e91..e562f60 100644
--- a/sdk/examples/machine_timer/main.c
+++ b/sdk/examples/machine_timer/main.c
@@ -34,20 +34,19 @@ int main()
     machine_timer_irq_enable(1);
     machine_timer_enable(1);
 
-    GPIO_REG(GPIO_CTRL) |= 0x1;  // set gpio0 output mode
+    gpio_output_enable(GPIO0);
 
     while (1) {
         // 500ms
         if (count == 50) {
             count = 0;
-            GPIO_REG(GPIO_DATA) ^= 0x1; // toggle led
+            gpio_data_toggle(GPIO0); // toggle led
         }
     }
 #endif
 }
 
-void timer_irq_handler() __attribute__((interrupt));
-void timer_irq_handler()
+__attribute__((interrupt)) void timer_irq_handler()
 {
     count++;
 
diff --git a/sdk/examples/timer_int/.gitignore b/sdk/examples/timer_int/.gitignore
deleted file mode 100644
index f8096ab..0000000
--- a/sdk/examples/timer_int/.gitignore
+++ /dev/null
@@ -1,8 +0,0 @@
-# Object files
-*.o
-*.ko
-*.obj
-*.bin
-*.dump
-*.mem
-timer_int
diff --git a/sdk/examples/timer_int/Makefile b/sdk/examples/timer_int/Makefile
deleted file mode 100644
index d398e00..0000000
--- a/sdk/examples/timer_int/Makefile
+++ /dev/null
@@ -1,20 +0,0 @@
-RISCV_ARCH := rv32im
-RISCV_ABI := ilp32
-RISCV_MCMODEL := medlow
-
-
-TARGET = timer_int
-
-
-CFLAGS += -DSIMULATION
-#CFLAGS += -Os
-#ASM_SRCS +=
-#LDFLAGS +=
-#INCLUDES += -I.
-
-C_SRCS := \
-	main.c \
-
-
-BSP_DIR = ../../bsp
-include ../../bsp/bsp.mk
diff --git a/sdk/examples/timer_int/README.md b/sdk/examples/timer_int/README.md
deleted file mode 100644
index aa8c119..0000000
--- a/sdk/examples/timer_int/README.md
+++ /dev/null
@@ -1 +0,0 @@
-定时器中断例程。
\ No newline at end of file
diff --git a/sdk/examples/timer_int/main.c b/sdk/examples/timer_int/main.c
deleted file mode 100644
index ada0ea5..0000000
--- a/sdk/examples/timer_int/main.c
+++ /dev/null
@@ -1,51 +0,0 @@
-#include <stdint.h>
-
-#include "../../bsp/include/timer.h"
-#include "../../bsp/include/gpio.h"
-#include "../../bsp/include/utils.h"
-
-
-static volatile uint32_t count;
-
-
-int main()
-{
-    count = 0;
-
-#ifdef SIMULATION
-    TIMER0_REG(TIMER0_VALUE) = 5000;    // 100us period
-    TIMER0_REG(TIMER0_CTRL) = 0x07;     // enable interrupt and start timer
-
-    while (1) {
-        if (count == 2) {
-            TIMER0_REG(TIMER0_CTRL) = 0x00;   // stop timer
-            count = 0;
-            // TODO: do something
-            set_test_pass();
-            break;
-        }
-    }
-#else
-    TIMER0_REG(TIMER0_VALUE) = 500000;  // 10ms period
-    TIMER0_REG(TIMER0_CTRL) = 0x07;     // enable interrupt and start timer
-
-    GPIO_REG(GPIO_CTRL) |= 0x1;  // set gpio0 output mode
-
-    while (1) {
-        // 500ms
-        if (count == 50) {
-            count = 0;
-            GPIO_REG(GPIO_DATA) ^= 0x1; // toggle led
-        }
-    }
-#endif
-
-    return 0;
-}
-
-void timer0_irq_handler()
-{
-    TIMER0_REG(TIMER0_CTRL) |= (1 << 2) | (1 << 0);  // clear int pending and start timer
-
-    count++;
-}