diff --git a/Adafruit_PCF8574.cpp b/Adafruit_PCF8574.cpp
index 22f02e1..7fa4d9e 100644
--- a/Adafruit_PCF8574.cpp
+++ b/Adafruit_PCF8574.cpp
@@ -47,7 +47,7 @@ Adafruit_PCF8574::Adafruit_PCF8574(void) {}
  *    @return True if initialization was successful, otherwise false.
  */
 bool Adafruit_PCF8574::begin(uint8_t i2c_address, TwoWire *wire) {
-  delete(i2c_dev);
+  delete (i2c_dev);
 
   i2c_dev = new Adafruit_I2CDevice(i2c_address, wire);
 
@@ -58,17 +58,33 @@ bool Adafruit_PCF8574::begin(uint8_t i2c_address, TwoWire *wire) {
   return true;
 }
 
-
+/*!
+ *    @brief  Write one 'byte' of data directly to the GPIO control register
+ *    @param  d The data to write
+ *    @return True if we were able to write the data successfully over I2C
+ */
 bool Adafruit_PCF8574::digitalWriteByte(uint8_t d) {
   _writebuf = d;
   return i2c_dev->write(&_writebuf, 1);
 }
 
+/*!
+ *    @brief  Read one 'byte' of data directly from the GPIO control register
+ *    @return The byte of data read from the device
+ */
 uint8_t Adafruit_PCF8574::digitalReadByte(void) {
   i2c_dev->read(&_readbuf, 1);
   return _readbuf;
 }
 
+/*!
+ *    @brief  Set one GPIO expander pin to 'high' (weak pullup) or 'low'
+ * (grounded)
+ *    @param  pinnum The GPIO pin number, from 0 to 7 inclusive
+ *    @param  val The boolean value to write: true means activate the pullup
+ *    and false means turn on the sinking transistor.
+ *    @return True if we were able to write the data successfully over I2C
+ */
 bool Adafruit_PCF8574::digitalWrite(uint8_t pinnum, bool val) {
   if (val) {
     _writebuf |= 1 << pinnum;
@@ -78,7 +94,15 @@ bool Adafruit_PCF8574::digitalWrite(uint8_t pinnum, bool val) {
   return i2c_dev->write(&_writebuf, 1);
 }
 
-
+/*!
+ *    @brief  Set one GPIO expander pin to 'output' (grounded) or 'input' (weak
+ * pullup)
+ *    @param  pinnum The GPIO pin number, from 0 to 7 inclusive
+ *    @param  val The value to write: INPUT or INPUT_PULLUP means activate the
+ * pullup and OUTPUT means turn on the sinking transistor, as this is an open
+ * drain device
+ *    @return True if we were able to write the data successfully over I2C
+ */
 bool Adafruit_PCF8574::pinMode(uint8_t pinnum, uint8_t val) {
   if ((val == INPUT) || (val == INPUT_PULLUP)) {
     _writebuf |= 1 << pinnum;
@@ -88,7 +112,12 @@ bool Adafruit_PCF8574::pinMode(uint8_t pinnum, uint8_t val) {
   return i2c_dev->write(&_writebuf, 1);
 }
 
-
+/*!
+ *    @brief  Get a GPIO expander pin value
+ *    @param  pinnum The GPIO pin number, from 0 to 7 inclusive
+ *    @return True if the pin logic is NOT ground, false if the pin logic is
+ * ground
+ */
 bool Adafruit_PCF8574::digitalRead(uint8_t pinnum) {
   i2c_dev->read(&_readbuf, 1);
   return (_readbuf >> pinnum) & 0x1;
diff --git a/Adafruit_PCF8574.h b/Adafruit_PCF8574.h
index 639909e..23fe40b 100644
--- a/Adafruit_PCF8574.h
+++ b/Adafruit_PCF8574.h
@@ -25,7 +25,6 @@
 
 #define PCF8574_I2CADDR_DEFAULT 0x20 ///< DS3502 default I2C address
 
-
 /*!
  *    @brief  Class that stores state and functions for interacting with
  *            the PCF8574 I2C Expander