diff --git a/bitvend/mdb.py b/bitvend/mdb.py
index f44da87..d6d3b4b 100644
--- a/bitvend/mdb.py
+++ b/bitvend/mdb.py
@@ -23,6 +23,7 @@ class BitvendCashlessMDBDevice(CashlessMDBDevice):
         # FIXME we report success here, because database write takes too much
         # time to respond in 5ms.
         self.send([0x05, 0x00, 0xff])
+        self.poll_queue.put([0x05])
         self.current_request.processed = True
 
         self.logger.info('got vend request: %r', self.current_tx_id)
diff --git a/mdb/backend.py b/mdb/backend.py
index 8e40da5..1fc686e 100644
--- a/mdb/backend.py
+++ b/mdb/backend.py
@@ -84,10 +84,15 @@ class RaspiBackend(Backend):
 #
 class SerialBackend(Backend):
     def __init__(self, device='/dev/ttyACM0'):
+        import serial
         self.ser = serial.Serial(device)
 
     def read(self):
-        return self.ser.read()
+        buf = b''
+        while len(buf) < 2:
+            buf += self.ser.read(1)
+        return buf
 
     def write(self, data):
         self.ser.write(data)
+        self.ser.flush()
diff --git a/mdb/device.py b/mdb/device.py
index 20ea546..6c27270 100644
--- a/mdb/device.py
+++ b/mdb/device.py
@@ -9,7 +9,7 @@ except ImportError:
 
 from mdb.utils import compute_checksum, compute_chk, bcd_decode
 from mdb.constants import *
-from mdb.backend import RaspiBackend, DummyBackend, pigpio
+from mdb.backend import RaspiBackend, DummyBackend, SerialBackend, pigpio
 
 class MDBRequest(object):
     timestamp = None
@@ -64,7 +64,7 @@ class MDBDevice(object):
             self.backend = RaspiBackend()
         else:
             self.logger.warning('Running with dummy backend device')
-            self.backend = DummyBackend()
+            self.backend = SerialBackend()
 
     def initialize(self):
         self.logger.info('Initializing...')
@@ -79,7 +79,8 @@ class MDBDevice(object):
             for b in range(0, len(data), 2):
                 if data[b+1]:
                     if self.current_request: # and not self.current_request.processed:
-                        self.logger.debug(self.current_request)
+                        if self.current_request.command not in [0xf2]:
+                            self.logger.debug(self.current_request)
                         if self.current_request.processed and self.current_request.ack:
                             self.logger.info('Got response: %d',self.current_request.data[-1])
                             self.poll_msg = []
@@ -150,21 +151,21 @@ class CashlessMDBDevice(MDBDevice):
 
     def process_request(self, req):
         # FIXME this shouldn't be required...
-        if req.command == 0x30 and req.validate_checksum():
-            self.lockup_counter += 1
+        #if req.command == 0x30 and req.validate_checksum():
+        #    self.lockup_counter += 1
 
-            if self.lockup_counter % 50 == 0:
-                self.logger.info('YOLO')
-                return []
-            return
-        if req.command == 0x31 and req.validate_checksum():
-            return []
-        if req.command == 0x37 and req.validate_checksum():
-            return []
-        if req.command == 0x36 and req.validate_checksum():
-            return []
-        if req.command == 0x34 and req.validate_checksum():
-            return []
+        #    if self.lockup_counter % 50 == 0:
+        #        self.logger.info('YOLO')
+        #        return []
+        #    return
+        #if req.command == 0x31 and req.validate_checksum():
+        #    return []
+        #if req.command == 0x37 and req.validate_checksum():
+        #    return []
+        #if req.command == 0x36 and req.validate_checksum():
+        #    return []
+        #if req.command == 0x34 and req.validate_checksum():
+        #    return []
 
         if (req.command & self.base_address) != self.base_address:
             # Target mismatch
diff --git a/requirements.txt b/requirements.txt
index aa7d3bd..c4d1399 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,6 +5,7 @@ Flask-Login==0.4.0
 Flask-QRcode==0.10.0
 Flask-SQLAlchemy==2.1
 Flask-WTF==0.14.2
+Flask-OAuthlib==0.9.4
 itsdangerous==0.24
 Jinja2==2.9.4
 MarkupSafe==0.23