Below is the code for displaying data on a monitor using Python and Tkinter on BeagleBone. It works great, but the text which displays the data flickers. Any ideas why?
#!/usr/bin/python
import alsaaudio as aa
import audioop
import Tkinter as tk
import tkFont
import threading
import Queue
started = False
class Display(object):
def __init__(self, parent, queue):
self.parent = parent
self.queue = queue
self._geom = '200x200+0+0'
parent.geometry("{0}x{1}+0+0".format(
parent.winfo_screenwidth(), parent.winfo_screenheight()))
parent.overrideredirect(1)
parent.title('Listen')
parent.configure(background='#000000')
parent.displayFont = tkFont.Font(family="Unit-Bold", size=150)
self.process_queue()
def process_queue(self):
try:
scaled_vol = self.queue.get(0)
self.print_message(scaled_vol)
except Queue.Empty:
pass
self.parent.after(100, self.process_queue)
def print_message(self, messageString):
print 'message', messageString
self.message = tk.Message(
self.parent, text=messageString, bg="#000000",
font=self.parent.displayFont, fg="#777777", justify="c")
self.message.place(relx=.5, rely=.5, anchor="c")
def setup_audio(queue, stop_event):
data_in = aa.PCM(aa.PCM_CAPTURE, aa.PCM_NONBLOCK, 'hw:1')
data_in.setchannels(2)
data_in.setrate(44100)
data_in.setformat(aa.PCM_FORMAT_S16_LE)
data_in.setperiodsize(256)
while not stop_event.is_set():
# Read data from device
l, data = data_in.read()
if l:
# catch frame error
try:
max_vol = audioop.rms(data, 2)
scaled_vol = max_vol // 4680
print scaled_vol
if scaled_vol <= 3:
# Too quiet, ignore
continue
total_vol += scaled_vol / 10.0
if started and total_vol > 200.0:
started = False
elif started:
queue.put(scaled_vol)
except audioop.error, e:
if e.message != "not a whole number of frames":
raise e
def main():
root = tk.Tk()
queue = Queue.Queue()
window = Display(root, queue)
stop_event = threading.Event()
audio_thread = threading.Thread(target=setup_audio,
args=[queue, stop_event])
audio_thread.start()
try:
root.mainloop()
finally:
stop_event.set()
audio_thread.join()
pass
if __name__ == '__main__':
main()
The monitor is 1920 x 1080. It is the only monitor I have to check it on.