| title | layout | meta-description | share | author | video | about | cats | simple-description | date | date-updated | |||
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Microbit Python Program with pySerial and GUIZero |
text-width-sidebar |
Using GUIZero & pySerial to send commands to the microbit. |
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jez |
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Using GUIZero---a learner-friendly tkinter wrapper---to create a serial connection to the microbit in Python with pySerial. |
python |
pySerial Microbit GUI |
2016-12-23 10:20:00 UTC |
2016-12-23 10:20:00 UTC |
{:.ui .image .small .floated .right}
It is possible to send commands to the microbit over a serial connection from your computer. The REPL function in the mu editor is simply a serial connection. For example, display.show(Image.HAPPY) causes a face to show on the microbit's display.
There's more about the USB serial connection on our website.
To send Python commands, the microbit must be running a micropython .hex file (eg, created in mu).
In this example, a Python GUI program sends commands to the microbit flashed in mu with a blank script.
This program uses two Python modules: pySerial and GUIZero.
-
pySerial handles the serial communication. It scans for the microbit and creates a serial connection.
-
GUIZero is for drawing the GUI. It is a learner-friendly wrapper for TKInter.
Handles the serial connection to the microbit.
def find_microbit_comport():
ports = list(list_ports.comports())
for p in ports:
if (p.pid == 516) and (p.vid == 3368):
return str(p.device)
This function returns a string of the microbit's COM port. On Windows this might be COM3, on Linux /dev/ttyS2.
The product ID & vendor ID of each attached device is evaluated. If it is the same as the ones on a microbit (516 & 3368) then return the device name (eg COM4).
serial.tools.list_ports must be imported.
Create a new instance of the Serial class as ser:
ser = serial.Serial()
Set ser baud rate to 115200. This is the default baud rate of the microbit:
ser.baudrate = 115200
Set the ser COM port to the one found by find_microbit_comport() .
ser.port = find_microbit_comport()
Before writing data the COM port must be opened. Serial.open() throws an exception if a connection cannot be made.
ser.open()
With the COM port open, we can write a command:
ser.write("display.show(Image.HAPPY) \r".encode() )
The \r is a carriage return. It tells REPL on the microbit that return has been pressed and it should execute the line sent.
.encode() turns the string into bytes.
GUI Zero is a learner-friendly wrapper for Tkinter. It allows beginners to easily create GUIs for the program by removing many of the complexities of Tkinter.
It's still at the beginning phase and I'm hoping this is the first program using it!
The program's window is an instance of the App class. In this example it's assigned to app.
app = App()
# The app window can be modified by with parameters.
# EG app = App(title="My Microbit Program") for a title.
# The width, height, and other things can be changed.
connect_button = PushButton(app, text="Connect", command=connect)
# create an instance of the PushButton class.
# The GUI parent (or master) is app (main app window).
# Text is "Connect"
# When it is clicked, connect() is executed
The final line is app.display(). This renders the GUI we have set up.
Box() in GUIZero extends the Frame class in Tkinter. It allows GUI elements such as PushButton() or ButtonGroup() to be arranged together.
button_box = Box(app)
In the example below, the connect and disconnect sit within the button_box instance of Box()
connect_button = PushButton(button_box, text="Connect", command=connect)
This allows the collection buttons to sit together in the GUI.
{% highlight python %}
from guizero import *
import serial from serial.serialutil import SerialException from serial.tools import list_ports
def connect(): try: ser.open() ser.write("from microbit import * \r".encode()) except SerialException: alerts.error(app, "No Connection! Unplug microbit and try again")
def disconnect(): ser.close()
""" send_data() run when send_button is clicked. Gets data from faces_to_send_list and writes to serial port as bytes
- .get selected face from faces_to_send_list
- convert to bytes
- .write to serial port
Alternatively, 1 + 2 + 3 all on the same: ser.write((faces_to_send_list.get() + '\r').encode()) """
def send_data(): command_to_send = faces_to_send_list.get() + '\r' command_to_send_bytes = command_to_send.encode() try: ser.write(command_to_send_bytes) except SerialException: alerts.error(app, "Could not Send. Connected?")
""" find_microbit_comport() returns COM port / device the microbit is attached to.
For each com port on the computer, check whether the attached device's product ID and vendor ID match the microbits. """
def find_microbit_comport(): ports = list(list_ports.comports()) for p in ports: if (p.pid == 516) and (p.vid == 3368): return str(p.device)
ser = serial.Serial() ser.baudrate = 115200 ser.port = find_microbit_comport()
app = App(layout='grid', height='300', width='200', title="Python Microbit Smile")
button_box = Box(app, grid=[0, 0])
connect_button = PushButton(button_box, text="Connect", command=connect, padx=3, pady=3)
disconnect_button = PushButton(button_box, text="Disconnect", command=disconnect, padx=3, pady=3)
face_box = Box(app, grid=[0, 1])
faces_to_send_list = ButtonGroup(face_box, [ ["Happy", "display.show(Image.HAPPY)"], ["Sad", "display.show(Image.SAD)"], ["Silly", "display.show(Image.SILLY)"], ["Yes", "display.show(Image.YES)"], ["No", "display.show(Image.NO)"], ["Pacman", "display.show(Image.PACMAN)"], ["Cow", "display.show(Image.COW)"] ], "display.show(Image.HAPPY)" )
send_button = PushButton(face_box, text="Send", command=send_data)
app.display()
{% endhighlight %}