diff --git a/app/src/async_ifc.py b/app/src/async_ifc.py
new file mode 100644
index 0000000..b0dde65
--- /dev/null
+++ b/app/src/async_ifc.py
@@ -0,0 +1,11 @@
+if __name__ == "app.src.async_ifc":
+    from app.src.byte_fifo import ByteFifo
+else:  # pragma: no cover
+    from byte_fifo import ByteFifo
+
+
+class AsyncIfc():
+    def __init__(self):
+        self.read = ByteFifo()
+        self.write = ByteFifo()
+        self.forward = ByteFifo()
diff --git a/app/src/byte_fifo.py b/app/src/byte_fifo.py
new file mode 100644
index 0000000..90eb8ba
--- /dev/null
+++ b/app/src/byte_fifo.py
@@ -0,0 +1,53 @@
+
+if __name__ == "app.src.byte_fifo":
+    from app.src.messages import hex_dump_str, hex_dump_memory
+else:  # pragma: no cover
+    from messages import hex_dump_str, hex_dump_memory
+
+
+class ByteFifo:
+    """ a byte FIFO buffer with trigger callback """
+    def __init__(self):
+        self.__buf = bytearray()
+        self.__trigger_cb = None
+
+    def reg_trigger(self, cb) -> None:
+        self.__trigger_cb = cb
+
+    def __iadd__(self, data):
+        self.__buf.extend(data)
+        return self
+
+    def __call__(self) -> None:
+        '''triggers the observer'''
+        if callable(self.__trigger_cb):
+            return self.__trigger_cb()
+
+    def get(self, size: int = None) -> bytearray:
+        '''removes size numbers of byte and return them'''
+        if not size:
+            data = self.__buf
+            self.clear()
+        else:
+            data = self.__buf[:size]
+            # The fast delete syntax
+            self.__buf[:size] = b''
+        return data
+
+    def peek(self, size: int = None) -> bytearray:
+        '''returns size numbers of byte without removing them'''
+        if not size:
+            return self.__buf
+        return self.__buf[:size]
+
+    def clear(self):
+        self.__buf = bytearray()
+
+    def __len__(self) -> int:
+        return len(self.__buf)
+
+    def __str__(self) -> str:
+        return hex_dump_str(self.__buf, self.__len__())
+
+    def logging(self, level, info):
+        hex_dump_memory(level, info, self.__buf, self.__len__())
diff --git a/app/tests/test_byte_fifo.py b/app/tests/test_byte_fifo.py
new file mode 100644
index 0000000..1544cc0
--- /dev/null
+++ b/app/tests/test_byte_fifo.py
@@ -0,0 +1,43 @@
+# test_with_pytest.py
+
+from app.src.byte_fifo import ByteFifo
+
+def test_fifo():
+    read = ByteFifo()
+    assert 0 == len(read)
+    read += b'12'
+    assert 2 == len(read)
+    read += bytearray("34", encoding='UTF8')
+    assert 4 == len(read)
+    assert b'12' == read.peek(2)
+    assert 4 == len(read)
+    assert b'1234' == read.peek()
+    assert 4 == len(read)
+    assert b'12' == read.get(2)
+    assert 2 == len(read)
+    assert b'34' == read.get()
+    assert 0 == len(read)
+
+def test_fifo_fmt():
+    read = ByteFifo()
+    read += b'1234'
+    assert b'1234' == read.peek()
+    assert "  0000 | 31 32 33 34                                      | 1234" == f'{read}'
+
+def test_fifo_observer():
+    read = ByteFifo()
+
+    def _read():
+        assert b'1234' == read.get(4)
+
+    read += b'12'
+    assert 2 == len(read)
+    read()
+    read.reg_trigger(_read)
+    read += b'34'
+    assert 4 == len(read)
+    read()
+    assert 0 == len(read)
+    assert b'' == read.peek(2)
+    assert b'' == read.get(2)
+    assert 0 == len(read)