Update README.md

README.md

@@ -1,6 +1,6 @@
 # micro:bit MicroPython Cookbook (Updating)
 
-A note for some Python tricks and experiments on BBC micro:bit.
+My notes for some Python tricks and experiments on BBC micro:bit, mostly written by me.
 
 ## Easer Eggs
 
@@ -19,10 +19,45 @@ this.authors()
 love.badaboom()
 ```
 
+## Why You Shouldn't Use *
+
+The following code
+
+```python
+from microbit import *
+```
+
+is a bad idea. This way imports everything of the microbit module even you don't need many of the features.
+
+Instead, you should only import sub-modules you actually use:
+
+```python
+from microbit import pin0, display, sleep
+```
+
+## How Much Memory Left?
+
+```python
+from micropython import mem_info
+
+print(mem_info(1))
+```
+
+You can also try to turn on garbage collection:
+
+```python
+import gc
+
+gc.enable() # auto memory recycle
+gc.collect() # force memory recycle
+```
+
 ## Some Lesser Known Facts
 
 Since Python and MicroPython are interpreted languages, they eat a lot of memory. Also, the hex file generated by micro:bit Python editors are consisted of 2 parts: the MicroPython firmware (up to 248 KB) and user's script (up to only 8 KB). See [Firmware Hex File](https://microbit-micropython.readthedocs.io/en/latest/devguide/hexformat.html). Which means it's not possible to build big projects with micro:bit's MicroPython.
 
+One way to "minimize" your script size is to use one-space indents instead of 4.
+
 Also, how micro:bit get its own version of MicroPython anyway: [The Story of MicroPython on the BBC micro:bit](http://ntoll.org/article/story-micropython-on-microbit) by Nicholas H. Tollervey, who also created the [Mu editor](https://codewith.mu/), which is easier to use than the official online editor.
 
 ## Fill LED Display
@@ -50,23 +85,65 @@ while True:
 
 ## A More Convenient Pin Class
 
-Use **namedtuple** to "rename" pin methods as set() and get().
+Make a Pin class to "rename" existing pin methods.
 
 ```python
-from microbit import pin0, sleep
+from microbit import pin0, pin2, sleep
+
+class Pin:
+    
+    __slot__ = ["pin"]
+    
+    def __init__(self, pin):
+        self.pin = pin
+    
+    def set(self, value):
+        self.pin.write_digital(value)
+    
+    def setPWM(self, value):
+        self.pin.write_analog(value)
+    
+    def get(self):
+        self.pin.set_pull(self.pin.PULL_DOWN)
+        return self.pin.read_digital()
+    
+    def pressed(self):
+        self.pin.set_pull(self.pin.PULL_UP)
+        return not self.pin.read_digital()
+        
+    def getADC(self):
+        return self.pin.read_analog()
+
+
+led = Pin(pin0)
+button = Pin(pin2)
+
+while True:
+    led.set(button.pressed())
+    sleep(50)
+```
+
+## Another Version of Pin Class
+
+Use **namedtuple** as a simple Pin class. Save more memory than regular class.
+
+```python
+from microbit import pin0, pin2, sleep
 from ucollections import namedtuple
 
 Pin = namedtuple('Pin', ['set', 'get'])
-setPin = lambda p: Pin(p.write_digital, p.read_digital)
+
+def setPin(pin, pull_up=False):
+    pin.set_pull(pin.PULL_UP if pull_up else pin.PULL_DOWN)
+    return Pin(pin.write_digital, pin.read_digital)
 
 
 led = setPin(pin0)
+button = setPin(pin2, pull_up=True)
 
 while True:
-    led.set(1)
-    sleep(500)
-    led.set(0)
-    sleep(500)
+    led.set(not button.get())
+    sleep(50)
 ```
 
 ## LED Bar Graph