diff --git a/example.py b/example.py
index 030d924..211ff3e 100755
--- a/example.py
+++ b/example.py
@@ -8,9 +8,11 @@
 import fake_rpi
 
 sys.modules['RPi'] = fake_rpi.RPi
+sys.modules['RPi.GPIO'] = fake_rpi.RPi.GPIO
 sys.modules['smbus'] = fake_rpi.smbus
 
 # Then keep the transparent import everywhere in the application and dependencies
+import RPi
 import RPi.GPIO as GPIO
 import smbus
 
@@ -43,3 +45,16 @@ def read_byte_data(self, a, b):
 i2c = MyBus()
 i2c.read_byte_data(1, 2)
 i2c.read_i2c_block_data(1, 2, 3)
+
+
+class MyGPIO(RPi._GPIO):
+    def setup(self, channel, state, initial=0, pull_up_down=None):
+        self._inputs[channel] = state
+
+
+GPIO = MyGPIO()
+GPIO.setmode(GPIO.BCM)
+GPIO.setup(21, 1)  # fake GPIO input is set to 1
+GPIO.setup(22, 0)  # fake GPIO input is set to 0
+b = GPIO.input(21)
+b = GPIO.input(22)
\ No newline at end of file
diff --git a/readme.md b/readme.md
index d50726d..43629d8 100644
--- a/readme.md
+++ b/readme.md
@@ -109,6 +109,25 @@ sm = MyBus()
 b = sm.read_byte_data(0x21, 0x32)  # read in a byte
 ```
 
+What if I need take control of `GPIO` input so that it returns
+non-random bit. Ok, then create a child of my `_GPIO` like
+below and modify the `setup` method:
+
+```python
+import RPi
+
+class MyGPIO(RPi._GPIO):
+    def setup(self, channel, state, initial=0, pull_up_down=None):
+        self._inputs[channel] = state
+
+GPIO = MyGPIO()
+GPIO.setmode(GPIO.BCM)
+GPIO.setup(21, 1)  # fake GPIO input is set to 1
+GPIO.setup(22, 1)  # fake GPIO input is set to 0
+b = GPIO.input(21)
+b = GPIO.input(22)
+```
+
 ### Printing On or Off
 
 Here is the output from `example.py` in the `git` repo when the printing