diff --git a/litescope/software/driver/la.py b/litescope/software/driver/la.py
index 18b2f48..48b1f08 100644
--- a/litescope/software/driver/la.py
+++ b/litescope/software/driver/la.py
@@ -125,16 +125,12 @@ class LiteScopeLADriver():
             print("saving to " + filename)
         name, ext = os.path.splitext(filename)
         if ext == ".vcd":
-            from litescope.software.dump.vcd import VCDDump
             dump = VCDDump()
         elif ext == ".csv":
-            from litescope.software.dump.csv import CSVDump
             dump = CSVDump()
         elif ext == ".py":
-            from litescope.software.dump.python import PythonDump
             dump = PythonDump()
         elif ext == ".sr":
-            from litescope.software.dump.sigrok import SigrokDump
             if self.samplerate is None:
                 raise ValueError("Unable to automatically retrieve clk_freq, clk_freq parameter required")
             dump = SigrokDump(samplerate=self.samplerate)
diff --git a/litescope/software/dump/__init__.py b/litescope/software/dump/__init__.py
index 20fb9b1..0183987 100644
--- a/litescope/software/dump/__init__.py
+++ b/litescope/software/dump/__init__.py
@@ -1,90 +1,5 @@
-def dec2bin(d, width=0):
-    if d == "x":
-        return "x"*width
-    elif d == 0:
-        b = "0"
-    else:
-        b = ""
-        while d != 0:
-            b = "01"[d&1] + b
-            d = d >> 1
-    return b.zfill(width)
-
-
-def get_bits(values, low, high=None):
-    r = []
-    if high is None:
-        high = low + 1
-    for val in values:
-        t = (val >> low) & (2**(high - low) - 1)
-        r.append(t)
-    return r
-
-
-class DumpData(list):
-    def __init__(self, width):
-        self.width = width
-
-    def __getitem__(self, key):
-        if isinstance(key, int):
-            return get_bits(self, key)
-        elif isinstance(key, slice):
-            if key.start != None:
-                start = key.start
-            else:
-                start = 0
-            if key.stop != None:
-                stop = key.stop
-            else:
-                stop = self.width
-            if stop > self.width:
-                stop = self.width
-            if key.step != None:
-                raise KeyError
-            return get_bits(self, start, stop)
-        else:
-            raise KeyError
-
-    def decode_rle(self):
-        datas = DumpData(self.width - 1)
-        last_data = 0
-        for data in self:
-            rle = data >> (self.width - 1)
-            data = data & (2**(self.width - 1) - 1)
-            if rle:
-                for i in range(data):
-                    datas.append(last_data)
-            else:
-                datas.append(data)
-                last_data = data
-        return datas
-
-
-class DumpVariable:
-    def __init__(self, name, width, values=[]):
-        self.width = width
-        self.name = name
-        self.values = [int(v)%2**width for v in values]
-
-    def __len__(self):
-        return len(self.values)
-
-
-class Dump:
-    def __init__(self):
-        self.variables = []
-
-    def add(self, variable):
-        self.variables.append(variable)
-
-    def add_from_layout(self, layout, variable):
-        i = 0
-        for s, n in layout:
-            self.add(DumpVariable(s, n, variable[i:i+n]))
-            i += n
-
-    def __len__(self):
-        l = 0
-        for variable in self.variables:
-            l = max(len(variable), l)
-        return l
+from litescope.software.dump.common import DumpData, DumpVariable, Dump
+from litescope.software.dump.csv import CSVDump
+from litescope.software.dump.python import PythonDump
+from litescope.software.dump.sigrok import SigrokDump
+from litescope.software.dump.vcd import VCDDump
diff --git a/litescope/software/dump/common.py b/litescope/software/dump/common.py
new file mode 100644
index 0000000..20fb9b1
--- /dev/null
+++ b/litescope/software/dump/common.py
@@ -0,0 +1,90 @@
+def dec2bin(d, width=0):
+    if d == "x":
+        return "x"*width
+    elif d == 0:
+        b = "0"
+    else:
+        b = ""
+        while d != 0:
+            b = "01"[d&1] + b
+            d = d >> 1
+    return b.zfill(width)
+
+
+def get_bits(values, low, high=None):
+    r = []
+    if high is None:
+        high = low + 1
+    for val in values:
+        t = (val >> low) & (2**(high - low) - 1)
+        r.append(t)
+    return r
+
+
+class DumpData(list):
+    def __init__(self, width):
+        self.width = width
+
+    def __getitem__(self, key):
+        if isinstance(key, int):
+            return get_bits(self, key)
+        elif isinstance(key, slice):
+            if key.start != None:
+                start = key.start
+            else:
+                start = 0
+            if key.stop != None:
+                stop = key.stop
+            else:
+                stop = self.width
+            if stop > self.width:
+                stop = self.width
+            if key.step != None:
+                raise KeyError
+            return get_bits(self, start, stop)
+        else:
+            raise KeyError
+
+    def decode_rle(self):
+        datas = DumpData(self.width - 1)
+        last_data = 0
+        for data in self:
+            rle = data >> (self.width - 1)
+            data = data & (2**(self.width - 1) - 1)
+            if rle:
+                for i in range(data):
+                    datas.append(last_data)
+            else:
+                datas.append(data)
+                last_data = data
+        return datas
+
+
+class DumpVariable:
+    def __init__(self, name, width, values=[]):
+        self.width = width
+        self.name = name
+        self.values = [int(v)%2**width for v in values]
+
+    def __len__(self):
+        return len(self.values)
+
+
+class Dump:
+    def __init__(self):
+        self.variables = []
+
+    def add(self, variable):
+        self.variables.append(variable)
+
+    def add_from_layout(self, layout, variable):
+        i = 0
+        for s, n in layout:
+            self.add(DumpVariable(s, n, variable[i:i+n]))
+            i += n
+
+    def __len__(self):
+        l = 0
+        for variable in self.variables:
+            l = max(len(variable), l)
+        return l
diff --git a/litescope/software/dump/csv.py b/litescope/software/dump/csv.py
index 7e575ea..93cad4f 100644
--- a/litescope/software/dump/csv.py
+++ b/litescope/software/dump/csv.py
@@ -1,4 +1,4 @@
-from litescope.software.dump import *
+from litescope.software.dump.common import Dump, dec2bin
 
 
 class CSVDump(Dump):
diff --git a/litescope/software/dump/python.py b/litescope/software/dump/python.py
index fb96e63..7150b4e 100644
--- a/litescope/software/dump/python.py
+++ b/litescope/software/dump/python.py
@@ -1,4 +1,4 @@
-from litescope.software.dump import *
+from litescope.software.dump.common import Dump
 
 
 class PythonDump(Dump):
diff --git a/litescope/software/dump/sigrok.py b/litescope/software/dump/sigrok.py
index a35c2d4..ecfcfb4 100644
--- a/litescope/software/dump/sigrok.py
+++ b/litescope/software/dump/sigrok.py
@@ -5,7 +5,7 @@ import zipfile
 import re
 from collections import OrderedDict
 
-from litescope.software.dump import *
+from litescope.software.dump.common import Dump, DumpVariable
 
 
 class SigrokDump(Dump):
diff --git a/litescope/software/dump/vcd.py b/litescope/software/dump/vcd.py
index 7f94354..55e0deb 100644
--- a/litescope/software/dump/vcd.py
+++ b/litescope/software/dump/vcd.py
@@ -1,5 +1,5 @@
 import datetime
-from litescope.software.dump import *
+from litescope.software.dump.common import Dump, dec2bin
 
 
 class VCDDump(Dump):
diff --git a/test/dump_tb.py b/test/dump_tb.py
index 3fb3067..abff5a1 100644
--- a/test/dump_tb.py
+++ b/test/dump_tb.py
@@ -10,19 +10,15 @@ dump.add(DumpVariable("sinus", 8, [128+128*sin(j/(2*pi*16)) for j in range(1024)
 dump.add(DumpVariable("cosinus", 8, [128+128*cos(j/(2*pi*16)) for j in range(1024)]))
 
 print("csv export test")
-from litescope.software.dump.csv import CSVDump
 CSVDump(dump).write("dump.csv")
 
 print("python export test...")
-from litescope.software.dump.python import PythonDump
 PythonDump(dump).write("dump.py")
 
-print("vcd export test...")
-from litescope.software.dump.vcd import VCDDump
-VCDDump(dump).write("dump.vcd")
-
 print("sigrok export/import test...")
-from litescope.software.dump.sigrok import SigrokDump
 SigrokDump(dump).write("dump.sr")
 SigrokDump(dump).read("dump.sr")
-SigrokDump(dump).write("dump.sr")
\ No newline at end of file
+SigrokDump(dump).write("dump.sr")
+
+print("vcd export test...")
+VCDDump(dump).write("dump.vcd")
\ No newline at end of file