diff --git a/src/tests/test_msg.py b/src/tests/test_msg.py
new file mode 100644
index 0000000000..9bc3e347cf
--- /dev/null
+++ b/src/tests/test_msg.py
@@ -0,0 +1,79 @@
+import sys
+sys.path.append('..')
+sys.path.append('../lib')
+import unittest
+
+from trezor import loop
+from trezor.msg import read_report, parse_header, read_message
+
+
+class TestMsg(unittest.TestCase):
+
+    def test_read_report(self):
+
+        reader = read_report()
+        syscall = reader.send(None)
+
+        self.assertIsInstance(syscall, loop.Select)
+        self.assertEqual(syscall.events, (loop.HID_READ,))
+
+        empty_report = b'\x3f' + b'\x00' * 63
+        try:
+            reader.send(empty_report)
+        except StopIteration as e:
+            result = e.value
+        self.assertEqual(result, empty_report)
+
+    def test_parse_header(self):
+
+        report = b'\x3f##\xab\xcd\x12\x34\x56\x78'
+        msgtype, msglen = parse_header(report)
+        self.assertEqual(msgtype, int('0xabcd', 16))
+        self.assertEqual(msglen, int('0x12345678', 16))
+
+    def test_read_message(self):
+
+        reader = read_message()
+        reader.send(None)
+
+        empty_message = b'\x3f##\xab\xcd\x00\x00\x00\x00' + b'\x00' * 55
+        try:
+            reader.send(empty_message)
+        except StopIteration as e:
+            restype, resmsg = e.value
+        self.assertEqual(restype, int('0xabcd', 16))
+        self.assertEqual(resmsg, b'')
+
+        reader = read_message()
+        reader.send(None)
+
+        content = bytes([x for x in range(0, 55)])
+        message = b'\x3f##\xab\xcd\x00\x00\x00\x37' + content
+        try:
+            reader.send(message)
+        except StopIteration as e:
+            restype, resmsg = e.value
+        self.assertEqual(restype, int('0xabcd', 16))
+        self.assertEqual(resmsg, content)
+
+        def chunks(l, n):
+            for i in range(0, len(l), n):
+                yield l[i:i + n]
+
+        reader = read_message()
+        reader.send(None)
+
+        content = bytes([x for x in range(0, 256)])
+        message = b'##\xab\xcd\x00\x00\x01\00' + content
+        reports = [b'\x3f' + ch + '\x00' * (63 - len(ch)) for ch in chunks(message, 63)]
+        try:
+            for report in reports:
+                reader.send(report)
+        except StopIteration as e:
+            restype, resmsg = e.value
+        self.assertEqual(restype, int('0xabcd', 16))
+        self.assertEqual(resmsg, content)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/src/trezor/msg.py b/src/trezor/msg.py
index f815899c3b..742cf81e36 100644
--- a/src/trezor/msg.py
+++ b/src/trezor/msg.py
@@ -1,9 +1,52 @@
+import ustruct
+
+from trezor import loop
+
 from TrezorMsg import Msg
 
 _msg = Msg()
 
+
 def select(timeout_us):
     return _msg.select(timeout_us)
 
+
 def send(msg):
     return _msg.send(msg)
+
+
+REPORT_LEN = 64
+REPORT_NUM = 63
+HEADER_MAGIC = 35  # '#'
+
+
+def read_report():
+    report = yield loop.Select(loop.HID_READ)
+    assert report[0] == REPORT_NUM, 'Malformed report number'
+    assert len(report) == REPORT_LEN, 'Incorrect report length'
+    return memoryview(report)
+
+
+def parse_header(report):
+    assert report[1] == HEADER_MAGIC and report[2] == HEADER_MAGIC, 'Header not found'
+    return ustruct.unpack_from('>HL', report, 3)
+
+
+def read_message():
+    report = yield from read_report()
+    (msgtype, msglen) = parse_header(report)
+
+    repdata = report[1 + 8:]
+    repdata = repdata[:msglen]
+    msgbuf = bytearray(repdata)
+
+    remaining = msglen - len(msgbuf)
+
+    while remaining > 0:
+        report = yield from read_report()
+        repdata = report[1:]
+        repdata = repdata[:remaining]
+        msgbuf.extend(repdata)
+        remaining -= len(repdata)
+
+    return (msgtype, msgbuf)