diff --git a/html/pymata4/private_constants.html b/html/pymata4/private_constants.html
index 18f9ae2..e55b86e 100644
--- a/html/pymata4/private_constants.html
+++ b/html/pymata4/private_constants.html
@@ -79,7 +79,7 @@ <h1 class="title">Module <code>pymata4.private_constants</code></h1>
     PWM_MESSAGE = 0xE0 # Firmata confusingly conflates analog input with PWM output
     REPORT_VERSION = 0xF9  # report protocol version
 
-    # start of FirmataPlus defined SYSEX commands
+    # start of FirmataExpress defined SYSEX commands
     KEEP_ALIVE = 0x50  # keep alive message
     ARE_YOU_THERE = 0x51  # poll for boards existence
     I_AM_HERE = 0x52  # response to poll
@@ -111,7 +111,7 @@ <h1 class="title">Module <code>pymata4.private_constants</code></h1>
     SYSEX_REALTIME = 0x7F  # MIDI Reserved for realtime messages
 
     # reserved for PyMata
-    PYMATA_EXPRESS_THREADED_VERSION = &#34;1.00&#34;
+    PYMATA_EXPRESS_THREADED_VERSION = &#34;1.01&#34;
 
     # each byte represents a digital port
     #  and its value contains the current port settings
@@ -206,7 +206,7 @@ <h2 class="section-title" id="header-classes">Classes</h2>
     PWM_MESSAGE = 0xE0 # Firmata confusingly conflates analog input with PWM output
     REPORT_VERSION = 0xF9  # report protocol version
 
-    # start of FirmataPlus defined SYSEX commands
+    # start of FirmataExpress defined SYSEX commands
     KEEP_ALIVE = 0x50  # keep alive message
     ARE_YOU_THERE = 0x51  # poll for boards existence
     I_AM_HERE = 0x52  # response to poll
@@ -238,7 +238,7 @@ <h2 class="section-title" id="header-classes">Classes</h2>
     SYSEX_REALTIME = 0x7F  # MIDI Reserved for realtime messages
 
     # reserved for PyMata
-    PYMATA_EXPRESS_THREADED_VERSION = &#34;1.00&#34;
+    PYMATA_EXPRESS_THREADED_VERSION = &#34;1.01&#34;
 
     # each byte represents a digital port
     #  and its value contains the current port settings
diff --git a/pymata4/private_constants.py b/pymata4/private_constants.py
index b1b4b0e..89f912b 100644
--- a/pymata4/private_constants.py
+++ b/pymata4/private_constants.py
@@ -70,7 +70,7 @@ class PrivateConstants:
     SYSEX_REALTIME = 0x7F  # MIDI Reserved for realtime messages
 
     # reserved for PyMata
-    PYMATA_EXPRESS_THREADED_VERSION = "1.01"
+    PYMATA_EXPRESS_THREADED_VERSION = "1.02"
 
     # each byte represents a digital port
     #  and its value contains the current port settings
diff --git a/pymata4/pymata4.py b/pymata4/pymata4.py
index 8cc8f40..6c4ca5c 100644
--- a/pymata4/pymata4.py
+++ b/pymata4/pymata4.py
@@ -790,8 +790,7 @@ def keep_alive(self, period=1, margin=.3):
         will physically reset itself.
 
         Frequency of keep alive transmission is calculated as follows:
-        keep_alive_sent = period - (period * margin)
-
+        keep_alive_sent = period - margin
 
         :param period: Time period between keepalives. Range is 0-10 seconds.
                        0 disables the keepalive mechanism.
@@ -1347,6 +1346,9 @@ def _digital_message(self, data):
             # get pin value
             value = port_data & 0x01
 
+            # retrieve previous value
+            last_value = self.digital_pins[pin].current_value
+
             # set the current value in the pin structure
             self.digital_pins[pin].current_value = value
             time_stamp = time.time()
@@ -1358,8 +1360,9 @@ def _digital_message(self, data):
             else:
                 message = [PrivateConstants.INPUT, pin, value, time_stamp]
 
-            if self.digital_pins[pin].cb:
-                self.digital_pins[pin].cb(message)
+            if last_value != value:
+                if self.digital_pins[pin].cb:
+                    self.digital_pins[pin].cb(message)
 
             port_data >>= 1
 
diff --git a/pypi_desc.md b/pypi_desc.md
index d0d2815..3b3a39f 100644
--- a/pypi_desc.md
+++ b/pypi_desc.md
@@ -18,7 +18,7 @@ Pymata4 is a Firmata client that, like its asyncio sibling,
      * **Piezo Tone Generation.**
      * **Baud rate of 115200**
 
-<h2><u>Major features</u></h2>
+### Major features
 
 * **Fully documented <a href="https://htmlpreview.github.com/?https://github.com/MrYsLab/pymata4/blob/master/html/pymata4/index.html" target="_blank">intuitive API</a>**
 
diff --git a/setup.py b/setup.py
index cec80db..b399d6e 100644
--- a/setup.py
+++ b/setup.py
@@ -11,7 +11,7 @@
     packages=['pymata4'],
     install_requires=['pyserial'],
 
-    version='1.01',
+    version='1.02',
     description="A Python Protocol Abstraction Library For Arduino Firmata",
     long_description=long_description,
     long_description_content_type='text/markdown',