display.py

#! /usr/bin/python3
import time
import threading
import liquidcrystal_i2c

DISPLAY_I2C_ADDRESS = 0x27
DISPLAY_I2C_PORT = 1
DISPLAY_COLUMNS = 20
DISPLAY_ROWS = 4

class Display (threading.Thread):
  def __init__(self, threadID, name):
    threading.Thread.__init__(self)
    self.threadID = threadID
    self.name = name  
    self.lcd = liquidcrystal_i2c.LiquidCrystal_I2C(DISPLAY_I2C_ADDRESS, DISPLAY_I2C_PORT, numlines=DISPLAY_ROWS)
    self.buffer = ["" for row in range(0, DISPLAY_ROWS)]
    self.changed = False

  def run(self):
    while True:
      if self.changed:
        for line_num in range(0, DISPLAY_ROWS):
          self.lcd.printline(line_num, self.buffer[line_num])
        self.changed = False
      time.sleep(0.1)

  def clear(self):
    self.buffer[0] = ""
    self.buffer[1] = ""
    self.buffer[2] = ""
    self.buffer[3] = ""
    self.changed = True

  def message(self, line_1:str="", line_2:str="", line_3:str="", line_4:str=""):
    self.buffer[0] = line_1.center(DISPLAY_COLUMNS)
    self.buffer[1] = line_2.center(DISPLAY_COLUMNS)
    self.buffer[2] = line_3.center(DISPLAY_COLUMNS)
    self.buffer[3] = line_4.center(DISPLAY_COLUMNS)
    self.changed = True

  def update(self, north:int, east:int, location:str, volume:int, station:str, arrows:bool):
    if north >= 0:
      self.buffer[0] = ("{:5.2f}N, ").format(north)
    else:
      self.buffer[0] = ("{:5.2f}S, ").format(abs(north))

    if east >= 0:
      self.buffer[0] += ("{:6.2f}E").format(east)
    else:
      self.buffer[0] += ("{:6.2f}W").format(abs(east))

    self.buffer[0] = self.buffer[0].center(DISPLAY_COLUMNS)
    self.buffer[1] = location.center(DISPLAY_COLUMNS)

    # Volume display
    self.buffer[2] = ""
    bar_length = (volume * DISPLAY_COLUMNS) // 100
    for i in range(bar_length):
      self.buffer[2] += "-"
    for i in range(bar_length, DISPLAY_COLUMNS):
      self.buffer[2] += " "

    if arrows:
      # Trim/pad the station name to fit arrows at each side of the display
      station = station[:(DISPLAY_COLUMNS - 4)]
      padding = DISPLAY_COLUMNS - 4 - len(station)
      start_padding = padding // 2
      end_padding = padding - start_padding
      while start_padding:
        station = " " + station
        start_padding -= 1
      while end_padding:
        station += " "
        end_padding -= 1

      station = "< " + station + " >"
    self.buffer[3] = station.center(DISPLAY_COLUMNS)

    self.changed = True

if __name__ == "__main__":
  try:
    display_thread = Display(1, "Display")
    display_thread.start()
    display_thread.update(51.45, -2.59, "Bristol, United Kingdom", 45, "BBC Radio Bristol", True)
    time.sleep(5)
    display_thread.update(0, 0, "Clearing in 2s...", 0, "", False)
    time.sleep(2)
    display_thread.clear()
  
  except:
    exit()