• write an application that interfaces with an device that I made

Unfortunately i still have to complete my input/output devices, anyway i already writed some of the firmwares so i was able to write an application to control and debug my output board.
I have previous expirience wi pyGTK so it was a easy choice... and python development can be very quick :)

First step is to call required libraries

import gi
import sys
import serial, time
import os

gi.require_version('Gtk', '3.0')
from gi.repository import Gtk

Then i set up the serial connection, serial device is hardcoded but i don't think it's a problem because it's easy to modify the script.
Anyway i thinking about implement serial device selection with a GUI.

os.system('clear')

#Set up serial connection options
ser = serial.Serial(
    port='/dev/ttyUSB0',
    baudrate=9600,
)

print(ser.name)

ser.isOpen()
time.sleep(1)

                

Here i build a new GTK window object, every GUI widget and logic in my simple application has to be here.
I can also set up default size of the window.

class MyWindow(Gtk.ApplicationWindow):
    def __init__(self, app):
        Gtk.Window.__init__(self, title="Led output debug", application=app)
        self.set_default_size(300, 100)
        self.set_border_width(10)

        self.box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=6)
        self.add(self.box)

                

This is a switch button to enable/disable LED output.
Whenever the button is pressed "on_enable_clicked" function is called.

        self.enable_switch = Gtk.Switch()
        self.enable_switch.set_active(False)

        self.enable_switch.connect("notify::active", self.on_enable_clicked)

        self.enable_frm = Gtk.Frame()
        self.enable_frm.set_label("Enable switch")
        self.box.pack_start(self.enable_frm, True, True, 0)
        self.enable_frm.add(self.enable_switch)

                

Here I set up the slider to control the Vu-meter like behaviour of the output device.
"on_scale_moved" function is called when the slider is moved.

        slider_options = Gtk.Adjustment(0, 0, 100, 5, 10, 0)
        self.led_scale = Gtk.Scale(
            orientation=Gtk.Orientation.HORIZONTAL, adjustment=slider_options)
        self.led_scale.set_digits(0)
        self.led_scale.set_hexpand(True)
        self.led_scale.set_valign(Gtk.Align.START)

        self.led_scale.connect("value-changed", self.on_scale_moved)

        self.slider_frm = Gtk.Frame()
        self.slider_frm.set_label("LED output slider")
        self.box.pack_end(self.slider_frm, True, True, 0)
        self.slider_frm.add(self.led_scale)

                

These are the function called by widgets, i print a message in the terminal for debug, set up a command and send it through serial.

    def on_enable_clicked(self, switch, gparam):
        if switch.get_active():
            state = "on"
        else:
            state = "off"
        print("Local software: LEDs " + state + ".")
        serialcmd = "enable_set:" + state + ";"
        ser.write(serialcmd.encode())
        time.sleep(1)

    def on_scale_moved(self, event):
        print("Local software: LED output slider was moved to " + str(int(self.led_scale.get_value())) + "%.")
        serialcmd = "output_set:"+str(int(self.led_scale.get_value()))+";"
        ser.write(serialcmd.encode())

                

For an easy application like this there is nothing important here, this is a standard code snippet to enable a GTK application.

class MyApplication(Gtk.Application):
    def __init__(self):
        Gtk.Application.__init__(self)

    def do_activate(self):
        win = MyWindow(self)
        win.show_all()

    def do_startup(self):
        Gtk.Application.do_startup(self)

                

Last step: initialize the application and handle the exis status when the window is closed.

app = MyApplication()
exit_status = app.run(sys.argv)
sys.exit(exit_status)

                

Simple screenshot.

Debug application sources