diff --git a/.gitignore b/.gitignore
index 0481b99..285397f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@
 !.gitignore
 !init.sh
 /fceux-am
+/nvboard
diff --git a/npc/Makefile b/npc/Makefile
index 4910019..a5b768d 100644
--- a/npc/Makefile
+++ b/npc/Makefile
@@ -1,9 +1,13 @@
 VSRC := $(wildcard vsrc/*.v)
 CPPSRC := $(addprefix $(PWD)/,$(wildcard csrc/*.cpp))
+CPPSRC += $(SRC_AUTO_BIND)
+NXDC_FILES = $(abspath constr/top.nxdc)
+
 PREFIX ?= build
 OBJDIR := $(PREFIX)/obj
 SUBMAKE := $(OBJDIR)/Vexample.mk
 VERILATOR_FLAGS := --cc --exe
+NVBOARD_HOME ?= $(abspath ../nvboard)
 
 all: sim
 
@@ -18,11 +22,17 @@ $(OBJDIR)/Vexample: $(SUBMAKE)
 	$(MAKE) -C $(OBJDIR) -f $(notdir $(SUBMAKE)) Vexample
 	
 $(SUBMAKE): $(VSRC) $(CPPSRC) $(OBJDIR)
-	verilator $(VERILATOR_FLAGS) --Mdir $(PWD)/$(OBJDIR) $(VSRC) $(CPPSRC)
+	verilator $(VERILATOR_FLAGS) \
+		--Mdir $(abspath $(OBJDIR)) $(VSRC) $(CPPSRC)
+# $(addprefix -CFLAGS , $(CXXFLAGS)) $(addprefix -LDFLAGS , $(LDFLAGS)) \ 
 
 $(OBJDIR):
 	mkdir -p $(OBJDIR)
 
+SRC_AUTO_BIND = $(abspath $(PREFIX)/auto_bind.cpp)
+$(SRC_AUTO_BIND): $(NXDC_FILES)
+	python3 $(NVBOARD_HOME)/scripts/auto_pin_bind.py $^ $@
+
 include ../Makefile
 
 .PHONY: clean 
diff --git a/npc/flake.nix b/npc/flake.nix
index 3c5c8af..f938820 100644
--- a/npc/flake.nix
+++ b/npc/flake.nix
@@ -14,7 +14,14 @@
             gtkwave
             gcc
             bear
+            clang-tools
+            rnix-lsp
           ];
+
+          nativeBuildInputs = with pkgs; [
+            python3
+          ];
+
           shellHook = ''
             export NEMU_HOME=/home/xin/repo/ysyx-workbench/nemu
           '';
diff --git a/npc/trace/main.cpp b/npc/trace/main.cpp
deleted file mode 100644
index a62b9be..0000000
--- a/npc/trace/main.cpp
+++ /dev/null
@@ -1,32 +0,0 @@
-#include "verilated_vcd_c.h"
-#include "Vexample.h"
-#include "verilated.h"
-
-int main(int argc, char **argv, char **env) {
-}
-
-int main(int argc, char **argv, char **env) {
-    Verilated::commandArgs(argc, argv);
-    Verilated::traceEverOn(true);
-    VerilatedVcdC* tfp = new VerilatedVcdC;
-    Vexample *top = new Vexample;
-    int round = 100;
-    while (round--) {
-        int a = rand() & 1;
-        int b = rand() & 1;
-        top->a = a;
-        top->b = b;
-        top->eval();
-        printf("a = %d, b = %d, f = %d\n", a, b, top->f);
-        assert(top->f == (a ^ b));
-    }
-    exit(0);
-    topp->trace (tfp, 99);
-    tfp->open ("obj_dir/t_trace_ena_cc/simx.vcd");
-    ...
-    while (sc_time_stamp() < sim_time && !Verilated::gotFinish()) {
-        main_time += #;
-        tfp->dump (main_time);
-    }
-    tfp->close();
-}
\ No newline at end of file