diff --git a/npc/csrc_nvboard/main.cpp b/npc/csrc_nvboard/main.cpp
index c1165d4..e9df24c 100644
--- a/npc/csrc_nvboard/main.cpp
+++ b/npc/csrc_nvboard/main.cpp
@@ -1,40 +1,55 @@
-#include <cstdlib>
+#include <VSegHandler.h>
 #include <cassert>
 #include <cstdlib>
+#include <nvboard.h>
 #include <verilated.h>
 #include <verilated_vcd_c.h>
-#include <nvboard.h>
-#include <VSegHandler.h>
 
 #ifndef VERILATOR_TOPMODULE
 #define VERILATOR_TOPMODULE VSegHandler
 #endif
 
-const int MAX_SIM_TIME=100;
+const int MAX_SIM_TIME = 100;
+int keycode = 0;
 
-void nvboard_bind_all_pins(VERILATOR_TOPMODULE* top);
-
-static void single_cycle(VERILATOR_TOPMODULE* top) {
-  top->clock = 0; top->eval();
-  top->clock = 1; top->eval();
+template <class F> void cycle(VERILATOR_TOPMODULE *top, F &&f) {
+  top->clock = 0;
+  top->eval();
+  f();
+  top->clock = 1;
+  top->eval();
 }
 
-static void reset(VERILATOR_TOPMODULE* top, int n) {
+void nvboard_bind_all_pins(VERILATOR_TOPMODULE *top);
+
+static void single_cycle(VERILATOR_TOPMODULE *top) {
+  top->clock = 0;
+  top->eval();
+  top->clock = 1;
+  top->eval();
+}
+
+static void reset(VERILATOR_TOPMODULE *top, int n) {
   top->reset = 1;
-  while (n -- > 0) single_cycle(top);
+  while (n-- > 0)
+    single_cycle(top);
   top->reset = 0;
 }
 
 int main(int argc, char **argv, char **env) {
-    VERILATOR_TOPMODULE *top = new VERILATOR_TOPMODULE;
+  VERILATOR_TOPMODULE *top = new VERILATOR_TOPMODULE;
 
-    nvboard_bind_all_pins(top);
-    nvboard_init();
-    reset(top, 10);
-    while (true) {
-        nvboard_update();
-        top->eval();
-        single_cycle(top);
-    }
-    delete top;
+  nvboard_bind_all_pins(top);
+  nvboard_init();
+  reset(top, 10);
+  while (true) {
+    nvboard_update();
+    cycle(top, [&] {
+      if (keycode != top->io_keycode_bits) {
+        printf("%d\n", top->io_keycode_bits);
+        keycode = top->io_keycode_bits;
+      }
+    });
+  }
+  delete top;
 }
\ No newline at end of file