### Project 4：Programmable Buttons

![](./media/Python_06be84fb.png)

1\.  **Description**

![](./media/Python_b6d60ae2.png)

Buttons can be used to control circuits. In an integrated circuit with a push button, the circuit is connected when pressing the button and but after release, it will break again. 

Both ends of the button like two mountains. There is a river in between. 
The internal metal piece connect the two sides to let the current pass, just like building a bridge to connect two mountains.

The internal structure of the button is shown as follows: before pressing the button, 1 ,2 , 3 and 4 are turned on. However, 1, 3 or 1, 4 or 2, 3 or 2 and 4 are disconnected, which is only enabled when the button is pressed. ![](./media/Python_d2a204e6.png)

Micro: Bit main board boasts three push buttons, two are programmable buttons(marked with A and B), and the one on the other side is a reset button. By pressing the two programmable buttons can input three different signals. We can press button A or B alone or press them together and the LED dot matrix shows A,B and AB respectively. Let’s get started. 

2\.  **Preparation**

A. Attach the micro:bit main board to your computer via the USB cable

B. Open the offline version of Mu.

3\.  **Test Code1**

Enter Mu software and open the file“Programmable Buttons-1\.py”to import the code. You can also input code in the editing window yourself.

(**Note: All words and symbols must be written in English.**)

![](./media/Python_2637f524.png)

```python
from microbit import *

while True:
    if button_a.is_pressed():
        display.show("A")
    elif button_a.is_pressed() and button_b.is_pressed():
        display.scroll("AB")
    elif button_b.is_pressed():
        display.show("B")
```
Click“Check”to examine errors in the code. The program proves wrong if underlines and cursors are shown. 

![](./media/Python_a0f284f3.png)

If the code is correct, connect the micro:bit to your computer and click“Flash”to download the code to the micro:bit board.

![](./media/Python_5694d3ce.png)

4\.  **Test Result1**

After downloading the code to the board successfully, **power on via micro USB cable or external power supply(turn the DIP switch to ON)**, and press the reset button on the board.

![Img](./media/Python_bb3e1312.png)

The 5*5 LED dot matrix shows “A”if button A is pressed, then“B” if button B is pressed, and “AB” if button A and B are pressed together.

5\.  **Test Code2**

Enter Mu software and open the file“Programmable Buttons-2\.py”to import the code. You can also input code in the editing window yourself.

(**Note: All words and symbols must be written in English.**)

![](./media/Python_1a1126f6.png)

![](./media/Python_94849305.png)

```python
from microbit import *
a = 0
b = 0
val1 = Image("00000:""00000:""00000:""00000:""00900")
val2 = Image("00000:""00000:""00000:""00900:""99999")
val3 = Image("00000:""00000:""00900:""99999:""99999")
val4 = Image("00000:""00900:""99999:""99999:""99999")
val5 = Image("00900:""99999:""99999:""99999:""99999")
val6 = Image("99999:""99999:""99999:""99999:""99999")
display.show(val1)

while True:
    while button_a.is_pressed() == True:
        sleep(10)
        if button_a.is_pressed() == False:
            a = a + 1
            if(a >= 5):
                a = 5
            break
    while button_b.is_pressed() == True:
        sleep(10)
        if button_b.is_pressed() == False:
            a = a - 1
            if(a <= 0):
                a = 0
            break
    if a == 0:
        display.show(val1)
    if a == 1:
        display.show(val2)
    if a == 2:
        display.show(val3)
    if a == 3:
        display.show(val4)
    if a == 4:
        display.show(val5)
    if a == 5:
        display.show(val6)
```
Click“Check”to examine errors in the code. The program proves wrong if underlines and cursors are shown. 

![](./media/Python_21771d90.png)

![Img](./media/Python_8d257384.png)

If the code is correct, connect the micro:bit to your computer and click“Flash”to download the code to the micro:bit board.

![](./media/Python_84ba8cde.png)

![Img](./media/Python_8d257384.png)

6\.  **Test Result2**

After downloading the code to the board successfully, **power on via micro USB cable or external power supply(turn the DIP switch to ON)**, and press the reset button on the board.

![Img](./media/Python_bb3e1312.png)

If the button A is pressed, the LEDs turning red increase while if the button B pressed, the LEDs turning red reduce.

7\.  **Code Explanation**

![Img](./media/Python_b33858dc.png)

![Img](./media/Python_32bd1cca.png)