diff --git a/micropython/usbd/cdc.py b/micropython/usbd/cdc.py
index e19337ffa..016500e99 100644
--- a/micropython/usbd/cdc.py
+++ b/micropython/usbd/cdc.py
@@ -8,6 +8,9 @@
     endpoint_descriptor,
     EP_IN_FLAG
 )
+
+from .midi import RingBuf
+
 from micropython import const
 import ustruct
 import time
@@ -44,13 +47,15 @@ class CDCControlInterface(USBInterface):
     def __init__(self, interface_str):
         super().__init__(_CDC_ITF_CONTROL_CLASS, _CDC_ITF_CONTROL_SUBCLASS,
                          _CDC_ITF_CONTROL_PROT)
+        self.ep_in = None
+
 
     def get_itf_descriptor(self, num_eps, itf_idx, str_idx):
         # CDC needs a Interface Association Descriptor (IAD)
         # first interface is zero, two interfaces in total
         desc = ustruct.pack("<BBBBBBBB", 8, _ITF_ASSOCIATION_DESC_TYPE, itf_idx, 2,
                             _CDC_ITF_CONTROL_CLASS, _CDC_ITF_CONTROL_SUBCLASS,
-                            _CDC_ITF_CONTROL_PROT, 0)  # "IAD"
+                            _CDC_ITF_CONTROL_PROT, 4)  # "IAD"
 
         itf, strs = super().get_itf_descriptor(num_eps, itf_idx, str_idx)
         desc += itf
@@ -59,12 +64,13 @@ def get_itf_descriptor(self, num_eps, itf_idx, str_idx):
         desc += ustruct.pack("<BBBH", 5, _CS_DESC_TYPE, 0, 0x0120)  # "Header"
         desc += ustruct.pack("<BBBBB", 5, _CS_DESC_TYPE, 1, 0, 1)   # "Call Management"
         desc += ustruct.pack("<BBBB", 4, _CS_DESC_TYPE, 2, 2)  # "Abstract Control"
-        desc += ustruct.pack("<BBBH", 5, _CS_DESC_TYPE, 6, itf_idx, 1)  # "Union"
+        desc += ustruct.pack("<BBBBB", 5, _CS_DESC_TYPE, 6, itf_idx, itf_idx+1)  # "Union"
         return desc, strs
 
     def get_endpoint_descriptors(self, ep_addr, str_idx):
-        self.ep_in = endpoint_descriptor((ep_addr + 1) | EP_IN_FLAG, "interrupt", 8, 16)
-        return (self.ep_in, [], ((ep_addr+1) | EP_IN_FLAG,))
+        self.ep_in = (ep_addr) | EP_IN_FLAG
+        desc = endpoint_descriptor(self.ep_in, "interrupt", 8, 16)
+        return (desc, [], (self.ep_in,))
 
 
 class CDCDataInterface(USBInterface):
@@ -74,33 +80,54 @@ def __init__(self, interface_str, timeout=1):
         super().__init__(_CDC_ITF_DATA_CLASS, _CDC_ITF_DATA_SUBCLASS,
                          _CDC_ITF_DATA_PROT)
         self.rx_buf = bytearray(256)
-        self.mv_buf = memoryview(self.rx_buf)
-        self.rx_done = False
-        self.rx_nbytes = 0
-        self.timeout = timeout
+        # self.mv_buf = memoryview(self.rx_buf)
+        # self.rx_done = False
+        # self.rx_nbytes = 0
+        # self.timeout = timeout
+        self.rb = RingBuf(256)
+        self.ep_in = None
+        self.ep_out = None
+        self.read_cd_started = False
 
     def get_endpoint_descriptors(self, ep_addr, str_idx):
-        self.ep_in = (ep_addr + 2) | EP_IN_FLAG
-        self.ep_out = (ep_addr + 2) & ~EP_IN_FLAG
+        # XXX OUT = 0x00 but is defined as 0x80?
+        self.ep_in = (ep_addr) | EP_IN_FLAG
+        self.ep_out = (ep_addr) & ~EP_IN_FLAG
+
         # one IN / OUT Endpoint
         e_out = endpoint_descriptor(self.ep_out, "bulk", 64, 0)
         e_in = endpoint_descriptor(self.ep_in, "bulk", 64, 0)
         return (e_out + e_in, [], (self.ep_out, self.ep_in))
 
     def write(self, data):
-        super().submit_xfer(self.ep_in, data)
-
-    def read(self, nbytes=0):
-        # XXX PoC.. When returning, it should probably
-        # copy it to a ringbuffer instead of leaving it here
-        super().submit_xfer(self.ep_out, self.rx_buf, self._cb_rx)
-        now = time.time()
-        self.rx_done = False
-        self.rx_nbytes = 0
-        while ((time.time() - now) < self.timeout) and not self.rx_done:
-            time.sleep_ms(10)
-        return bytes(self.mv_buf[:self.rx_nbytes]) if self.rx_done else None
+        # we are just going to ignore any sends before it's time
+        if self.ep_in == None:
+            return
+        self.submit_xfer(self.ep_in, data)
+
+    # read nbytes or until stop char is found
+    def read(self, nbytes=1, stop=None):
+
+        if self.read_cd_started == False:
+            if self.ep_out == None:
+                # ep_out hasn't been set yet, so we can't start recv'ing
+                return b'' # TODO: better output then just an empty message?
+            self._start_rx_cb()
+            self.read_cd_started = True
+        res = bytearray()
+        for i in range(nbytes):
+            nxt = self.rb.get()
+            if nxt == None:
+                break
+            res.append(nxt)
+            if nxt == ord(stop):
+                break
+        return res
+
+    def _start_rx_cb(self):
+        self.submit_xfer(self.ep_out, self.rx_buf, self._cb_rx)
 
     def _cb_rx(self, ep, res, num_bytes):
-        self.rx_done = True
-        self.rx_nbytes = num_bytes
+        for i in range(0, num_bytes):
+            self.rb.put(self.rx_buf[i])
+        self.submit_xfer(self.ep_out, self.rx_buf, self._cb_rx)