diff --git a/adafruit_azureiot/device_registration.py b/adafruit_azureiot/device_registration.py
index 9071981..e5fa2c5 100644
--- a/adafruit_azureiot/device_registration.py
+++ b/adafruit_azureiot/device_registration.py
@@ -28,7 +28,7 @@ class DeviceRegistrationError(Exception):
     An error from the device registration
     """
 
-    def __init__(self, message):
+    def __init__(self, message: str):
         super().__init__(message)
         self.message = message
 
diff --git a/adafruit_azureiot/hmac.py b/adafruit_azureiot/hmac.py
index 64e72ed..7c4132e 100644
--- a/adafruit_azureiot/hmac.py
+++ b/adafruit_azureiot/hmac.py
@@ -16,8 +16,13 @@
 
 # pylint: disable=C0103, W0108, R0915, C0116, C0115
 
+try:
+    from typing import Union
+except ImportError:
+    pass
 
-def __translate(key, translation):
+
+def __translate(key: Union[bytes, bytearray], translation: bytes) -> bytes:
     return bytes(translation[x] for x in key)
 
 
@@ -28,7 +33,7 @@ def __translate(key, translation):
 SHA_DIGESTSIZE = 32
 
 
-def new_shaobject():
+def new_shaobject() -> dict:
     """Struct. for storing SHA information."""
     return {
         "digest": [0] * 8,
@@ -40,7 +45,7 @@ def new_shaobject():
     }
 
 
-def sha_init():
+def sha_init() -> dict:
     """Initialize the SHA digest."""
     sha_info = new_shaobject()
     sha_info["digest"] = [
@@ -73,7 +78,7 @@ def sha_init():
 Gamma1 = lambda x: (S(x, 17) ^ S(x, 19) ^ R(x, 10))
 
 
-def sha_transform(sha_info):
+def sha_transform(sha_info: dict) -> None:
     W = []
 
     d = sha_info["data"]
@@ -90,7 +95,7 @@ def sha_transform(sha_info):
     ss = sha_info["digest"][:]
 
     # pylint: disable=too-many-arguments, line-too-long
-    def RND(a, b, c, d, e, f, g, h, i, ki):
+    def RND(a, b, c, d, e, f, g, h, i, ki):  # type: ignore[no-untyped-def]
         """Compress"""
         t0 = h + Sigma1(e) + Ch(e, f, g) + ki + W[i]
         t1 = Sigma0(a) + Maj(a, b, c)
@@ -298,7 +303,7 @@ def RND(a, b, c, d, e, f, g, h, i, ki):
     sha_info["digest"] = dig
 
 
-def sha_update(sha_info, buffer):
+def sha_update(sha_info: dict, buffer: Union[bytes, bytearray]) -> None:
     """Update the SHA digest.
     :param dict sha_info: SHA Digest.
     :param str buffer: SHA buffer size.
@@ -346,13 +351,13 @@ def sha_update(sha_info, buffer):
     sha_info["local"] = count
 
 
-def getbuf(s):
+def getbuf(s: Union[str, bytes, bytearray]) -> Union[bytes, bytearray]:
     if isinstance(s, str):
         return s.encode("ascii")
     return bytes(s)
 
 
-def sha_final(sha_info):
+def sha_final(sha_info: dict) -> bytes:
     """Finish computing the SHA Digest."""
     lo_bit_count = sha_info["count_lo"]
     hi_bit_count = sha_info["count_hi"]
@@ -393,28 +398,28 @@ class sha256:
     block_size = SHA_BLOCKSIZE
     name = "sha256"
 
-    def __init__(self, s=None):
+    def __init__(self, s: Union[str, bytes, bytearray] = None):
         """Constructs a SHA256 hash object."""
         self._sha = sha_init()
         if s:
             sha_update(self._sha, getbuf(s))
 
-    def update(self, s):
+    def update(self, s: Union[str, bytes, bytearray]) -> None:
         """Updates the hash object with a bytes-like object, s."""
         sha_update(self._sha, getbuf(s))
 
-    def digest(self):
+    def digest(self) -> bytes:
         """Returns the digest of the data passed to the update()
         method so far."""
         return sha_final(self._sha.copy())[: self._sha["digestsize"]]
 
-    def hexdigest(self):
+    def hexdigest(self) -> str:
         """Like digest() except the digest is returned as a string object of
         double length, containing only hexadecimal digits.
         """
         return "".join(["%.2x" % i for i in self.digest()])
 
-    def copy(self):
+    def copy(self) -> "sha256":
         """Return a copy (“clone”) of the hash object."""
         new = sha256()
         new._sha = self._sha.copy()
@@ -429,7 +434,9 @@ class HMAC:
 
     blocksize = 64  # 512-bit HMAC; can be changed in subclasses.
 
-    def __init__(self, key, msg=None):
+    def __init__(
+        self, key: Union[bytes, bytearray], msg: Union[bytes, bytearray] = None
+    ):
         """Create a new HMAC object.
 
         key:       key for the keyed hash object.
@@ -478,15 +485,15 @@ def __init__(self, key, msg=None):
             self.update(msg)
 
     @property
-    def name(self):
+    def name(self) -> str:
         """Return the name of this object"""
         return "hmac-" + self.inner.name
 
-    def update(self, msg):
+    def update(self, msg: Union[bytes, bytearray]) -> None:
         """Update this hashing object with the string msg."""
         self.inner.update(msg)
 
-    def copy(self):
+    def copy(self) -> "HMAC":
         """Return a separate copy of this hashing object.
 
         An update to this copy won't affect the original object.
@@ -499,7 +506,7 @@ def copy(self):
         other.outer = self.outer.copy()
         return other
 
-    def _current(self):
+    def _current(self) -> "sha256":
         """Return a hash object for the current state.
 
         To be used only internally with digest() and hexdigest().
@@ -508,7 +515,7 @@ def _current(self):
         hmac.update(self.inner.digest())
         return hmac
 
-    def digest(self):
+    def digest(self) -> bytes:
         """Return the hash value of this hashing object.
 
         This returns a string containing 8-bit data.  The object is
@@ -518,13 +525,15 @@ def digest(self):
         hmac = self._current()
         return hmac.digest()
 
-    def hexdigest(self):
+    def hexdigest(self) -> str:
         """Like digest(), but returns a string of hexadecimal digits instead."""
         hmac = self._current()
         return hmac.hexdigest()
 
 
-def new_hmac(key, msg=None):
+def new_hmac(
+    key: Union[bytes, bytearray], msg: Union[bytes, bytearray] = None
+) -> "HMAC":
     """Create a new hashing object and return it.
 
     key: The starting key for the hash.
diff --git a/adafruit_azureiot/iothub_device.py b/adafruit_azureiot/iothub_device.py
index b5f01ec..274b8c4 100755
--- a/adafruit_azureiot/iothub_device.py
+++ b/adafruit_azureiot/iothub_device.py
@@ -12,13 +12,18 @@
 * Author(s): Jim Bennett, Elena Horton
 """
 
+try:
+    from typing import Any, Callable, Mapping, Union
+except ImportError:
+    pass
+
 import json
 import adafruit_logging as logging
 from .iot_error import IoTError
 from .iot_mqtt import IoTMQTT, IoTMQTTCallback, IoTResponse
 
 
-def _validate_keys(connection_string_parts):
+def _validate_keys(connection_string_parts: Mapping) -> None:
     """Raise ValueError if incorrect combination of keys"""
     host_name = connection_string_parts.get(HOST_NAME)
     shared_access_key_name = connection_string_parts.get(SHARED_ACCESS_KEY_NAME)
@@ -67,7 +72,7 @@ def connection_status_change(self, connected: bool) -> None:
             self._on_connection_status_changed(connected)
 
     # pylint: disable=W0613, R0201
-    def direct_method_invoked(self, method_name: str, payload) -> IoTResponse:
+    def direct_method_invoked(self, method_name: str, payload: str) -> IoTResponse:
         """Called when a direct method is invoked
         :param str method_name: The name of the method that was invoked
         :param str payload: The payload with the message
@@ -91,7 +96,10 @@ def cloud_to_device_message_received(self, body: str, properties: dict) -> None:
             self._on_cloud_to_device_message_received(body, properties)
 
     def device_twin_desired_updated(
-        self, desired_property_name: str, desired_property_value, desired_version: int
+        self,
+        desired_property_name: str,
+        desired_property_value: Any,
+        desired_version: int,
     ) -> None:
         """Called when the device twin desired properties are updated
         :param str desired_property_name: The name of the desired property that was updated
@@ -107,7 +115,7 @@ def device_twin_desired_updated(
     def device_twin_reported_updated(
         self,
         reported_property_name: str,
-        reported_property_value,
+        reported_property_value: Any,
         reported_version: int,
     ) -> None:
         """Called when the device twin reported values are updated
@@ -175,21 +183,23 @@ def __init__(
         self._mqtt = None
 
     @property
-    def on_connection_status_changed(self):
+    def on_connection_status_changed(self) -> Callable:
         """A callback method that is called when the connection status is changed. This method should have the following signature:
         def connection_status_changed(connected: bool) -> None
         """
         return self._on_connection_status_changed
 
     @on_connection_status_changed.setter
-    def on_connection_status_changed(self, new_on_connection_status_changed):
+    def on_connection_status_changed(
+        self, new_on_connection_status_changed: Callable
+    ) -> None:
         """A callback method that is called when the connection status is changed. This method should have the following signature:
         def connection_status_changed(connected: bool) -> None
         """
         self._on_connection_status_changed = new_on_connection_status_changed
 
     @property
-    def on_direct_method_invoked(self):
+    def on_direct_method_invoked(self) -> Callable:
         """A callback method that is called when a direct method is invoked.  This method should have the following signature:
         def direct_method_invoked(method_name: str, payload: str) -> IoTResponse:
 
@@ -202,7 +212,7 @@ def direct_method_invoked(method_name: str, payload: str) -> IoTResponse:
         return self._on_direct_method_invoked
 
     @on_direct_method_invoked.setter
-    def on_direct_method_invoked(self, new_on_direct_method_invoked):
+    def on_direct_method_invoked(self, new_on_direct_method_invoked: Callable) -> None:
         """A callback method that is called when a direct method is invoked.  This method should have the following signature:
         def direct_method_invoked(method_name: str, payload: str) -> IoTResponse:
 
@@ -215,7 +225,7 @@ def direct_method_invoked(method_name: str, payload: str) -> IoTResponse:
         self._on_direct_method_invoked = new_on_direct_method_invoked
 
     @property
-    def on_cloud_to_device_message_received(self):
+    def on_cloud_to_device_message_received(self) -> Callable:
         """A callback method that is called when a cloud to device message is received. This method should have the following signature:
         def cloud_to_device_message_received(body: str, properties: dict) -> None:
         """
@@ -223,8 +233,8 @@ def cloud_to_device_message_received(body: str, properties: dict) -> None:
 
     @on_cloud_to_device_message_received.setter
     def on_cloud_to_device_message_received(
-        self, new_on_cloud_to_device_message_received
-    ):
+        self, new_on_cloud_to_device_message_received: Callable
+    ) -> None:
         """A callback method that is called when a cloud to device message is received. This method should have the following signature:
         def cloud_to_device_message_received(body: str, properties: dict) -> None:
         """
@@ -233,7 +243,7 @@ def cloud_to_device_message_received(body: str, properties: dict) -> None:
         )
 
     @property
-    def on_device_twin_desired_updated(self):
+    def on_device_twin_desired_updated(self) -> Callable:
         """A callback method that is called when the desired properties of the devices device twin are updated.
         This method should have the following signature:
         def device_twin_desired_updated(desired_property_name: str, desired_property_value, desired_version: int) -> None:
@@ -241,7 +251,9 @@ def device_twin_desired_updated(desired_property_name: str, desired_property_val
         return self._on_device_twin_desired_updated
 
     @on_device_twin_desired_updated.setter
-    def on_device_twin_desired_updated(self, new_on_device_twin_desired_updated):
+    def on_device_twin_desired_updated(
+        self, new_on_device_twin_desired_updated: Callable
+    ) -> None:
         """A callback method that is called when the desired properties of the devices device twin are updated.
         This method should have the following signature:
         def device_twin_desired_updated(desired_property_name: str, desired_property_value, desired_version: int) -> None:
@@ -252,7 +264,7 @@ def device_twin_desired_updated(desired_property_name: str, desired_property_val
             self._mqtt.subscribe_to_twins()
 
     @property
-    def on_device_twin_reported_updated(self):
+    def on_device_twin_reported_updated(self) -> Callable:
         """A callback method that is called when the reported properties of the devices device twin are updated.
         This method should have the following signature:
         def device_twin_reported_updated(reported_property_name: str, reported_property_value, reported_version: int) -> None:
@@ -260,7 +272,9 @@ def device_twin_reported_updated(reported_property_name: str, reported_property_
         return self._on_device_twin_reported_updated
 
     @on_device_twin_reported_updated.setter
-    def on_device_twin_reported_updated(self, new_on_device_twin_reported_updated):
+    def on_device_twin_reported_updated(
+        self, new_on_device_twin_reported_updated: Callable
+    ) -> None:
         """A callback method that is called when the reported properties of the devices device twin are updated.
         This method should have the following signature:
         def device_twin_reported_updated(reported_property_name: str, reported_property_value, reported_version: int) -> None:
@@ -327,7 +341,9 @@ def is_connected(self) -> bool:
 
         return False
 
-    def send_device_to_cloud_message(self, message, system_properties=None) -> None:
+    def send_device_to_cloud_message(
+        self, message: Union[str, dict], system_properties: dict = None
+    ) -> None:
         """Send a device to cloud message from this device to Azure IoT Hub
         :param message: The message data as a JSON string or a dictionary
         :param system_properties: System properties to send with the message
@@ -339,7 +355,7 @@ def send_device_to_cloud_message(self, message, system_properties=None) -> None:
 
         self._mqtt.send_device_to_cloud_message(message, system_properties)
 
-    def update_twin(self, patch) -> None:
+    def update_twin(self, patch: Union[str, dict]) -> None:
         """Updates the reported properties in the devices device twin
         :param patch: The JSON patch to apply to the device twin reported properties
         """
diff --git a/adafruit_azureiot/quote.py b/adafruit_azureiot/quote.py
index a39b7ee..2a5cfbb 100644
--- a/adafruit_azureiot/quote.py
+++ b/adafruit_azureiot/quote.py
@@ -11,6 +11,12 @@
 safe arg.
 
 """
+
+try:
+    from typing import Any, Union
+except ImportError:
+    pass
+
 _ALWAYS_SAFE = frozenset(
     b"ABCDEFGHIJKLMNOPQRSTUVWXYZ" b"abcdefghijklmnopqrstuvwxyz" b"0123456789" b"_.-~"
 )
@@ -18,7 +24,7 @@
 SAFE_QUOTERS = {}
 
 
-def quote(bytes_val: bytes, safe="/"):
+def quote(bytes_val: bytes, safe: Union[str, bytes, bytearray] = "/") -> str:
     """The quote function %-escapes all characters that are neither in the
     unreserved chars ("always safe") nor the additional chars set via the
     safe arg.
@@ -69,17 +75,17 @@ class defaultdict:
 
     @staticmethod
     # pylint: disable=W0613
-    def __new__(cls, default_factory=None, **kwargs):
+    def __new__(cls, default_factory: Any = None, **kwargs: Any) -> "defaultdict":
         self = super(defaultdict, cls).__new__(cls)
         # pylint: disable=C0103
         self.d = {}
         return self
 
-    def __init__(self, default_factory=None, **kwargs):
+    def __init__(self, default_factory: Any = None, **kwargs: Any):
         self.d = kwargs
         self.default_factory = default_factory
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: Any) -> Any:
         try:
             return self.d[key]
         except KeyError:
@@ -87,16 +93,16 @@ def __getitem__(self, key):
             self.d[key] = val
             return val
 
-    def __setitem__(self, key, val):
+    def __setitem__(self, key: Any, val: Any) -> None:
         self.d[key] = val
 
-    def __delitem__(self, key):
+    def __delitem__(self, key: Any) -> None:
         del self.d[key]
 
-    def __contains__(self, key):
+    def __contains__(self, key: Any) -> bool:
         return key in self.d
 
-    def __missing__(self, key):
+    def __missing__(self, key: Any) -> Any:
         if self.default_factory is None:
             raise KeyError(key)
         return self.default_factory()
@@ -111,12 +117,12 @@ class Quoter(defaultdict):
 
     # Keeps a cache internally, using defaultdict, for efficiency (lookups
     # of cached keys don't call Python code at all).
-    def __init__(self, safe):
+    def __init__(self, safe: Union[bytes, bytearray]):
         """safe: bytes object."""
         super().__init__()
         self.safe = _ALWAYS_SAFE.union(safe)
 
-    def __missing__(self, b):
+    def __missing__(self, b: int) -> str:
         # Handle a cache miss. Store quoted string in cache and return.
         res = chr(b) if b in self.safe else "%{:02X}".format(b)
         self[b] = res