Better error management: send all requests to display before exit

Author: mathoudebine

library/display.py

@@ -1,5 +1,4 @@
 from library import config
-from library.lcd_comm import Orientation
 from library.lcd_comm_rev_a import LcdCommRevA
 from library.lcd_comm_rev_b import LcdCommRevB
 
@@ -25,15 +24,11 @@ def __init__(self):
             print("Unknown display revision '", CONFIG_DATA["display"]["REVISION"], "'")
 
     def initialize_display(self):
-        # Send initialization commands
-        self.lcd.InitializeComm()
-
-        # Reset screen in case it was in an unstable state
+        # Reset screen in case it was in an unstable state (screen is also cleared)
         self.lcd.Reset()
 
-        # Clear screen (blank)
-        self.lcd.SetOrientation(Orientation.PORTRAIT)  # Bug: orientation needs to be PORTRAIT before clearing
-        self.lcd.Clear()
+        # Send initialization commands
+        self.lcd.InitializeComm()
 
         # Set brightness
         self.lcd.SetBrightness()

library/lcd_comm.py

@@ -1,5 +1,7 @@
 from abc import ABC, abstractmethod
 from enum import IntEnum
+
+import serial
 from PIL import Image, ImageDraw, ImageFont
 
 from library import config
@@ -44,6 +46,21 @@ def get_height() -> int:
 
 
 class LcdComm(ABC):
+    def openSerial(self):
+        if CONFIG_DATA['config']['COM_PORT'] == 'AUTO':
+            lcd_com_port = self.auto_detect_com_port()
+            self.lcd_serial = serial.Serial(lcd_com_port, 115200, timeout=1, rtscts=1)
+            print(f"Auto detected comm port: {lcd_com_port}")
+        else:
+            lcd_com_port = CONFIG_DATA["config"]["COM_PORT"]
+            print(f"Static comm port: {lcd_com_port}")
+            self.lcd_serial = serial.Serial(lcd_com_port, 115200, timeout=1, rtscts=1)
+
+    @staticmethod
+    @abstractmethod
+    def auto_detect_com_port():
+        pass
+
     @abstractmethod
     def InitializeComm(self):
         pass

library/lcd_comm_rev_a.py

@@ -1,6 +1,6 @@
 import struct
+import time
 
-import serial
 from serial.tools.list_ports import comports
 
 from library.lcd_comm import *
@@ -19,15 +19,14 @@ class Command(IntEnum):
 
 class LcdCommRevA(LcdComm):
     def __init__(self):
-        self.lcd_serial = None
-        if CONFIG_DATA['config']['COM_PORT'] == 'AUTO':
-            lcd_com_port = self.auto_detect_com_port()
-            self.lcd_serial = serial.Serial(lcd_com_port, 115200, timeout=1, rtscts=1)
-            print(f"Auto detected comm port: {lcd_com_port}")
-        else:
-            lcd_com_port = CONFIG_DATA["config"]["COM_PORT"]
-            print(f"Static comm port: {lcd_com_port}")
-            self.lcd_serial = serial.Serial(lcd_com_port, 115200, timeout=1, rtscts=1)
+        self.openSerial()
+
+    def __del__(self):
+        try:
+            print("close serial")
+            self.lcd_serial.close()
+        except:
+            pass
 
     @staticmethod
     def auto_detect_com_port():
@@ -40,7 +39,7 @@ def auto_detect_com_port():
 
         return auto_com_port
 
-    def SendCommand(self, cmd: Command, x: int, y: int, ex: int, ey: int):
+    def SendCommand(self, cmd: Command, x: int, y: int, ex: int, ey: int, bypass_queue: bool = False):
         byteBuffer = bytearray(6)
         byteBuffer[0] = (x >> 2)
         byteBuffer[1] = (((x & 3) << 6) + (y >> 4))
@@ -49,9 +48,12 @@ def SendCommand(self, cmd: Command, x: int, y: int, ex: int, ey: int):
         byteBuffer[4] = (ey & 255)
         byteBuffer[5] = cmd
 
-        # Lock queue mutex then queue the request
-        with config.update_queue_mutex:
-            config.update_queue.put((self.WriteData, [byteBuffer]))
+        if bypass_queue:
+            self.WriteData(byteBuffer)
+        else:
+            # Lock queue mutex then queue the request
+            with config.update_queue_mutex:
+                config.update_queue.put((self.WriteData, [byteBuffer]))
 
     def WriteData(self, byteBuffer: bytearray):
         try:
@@ -75,10 +77,17 @@ def InitializeComm(self):
         pass
 
     def Reset(self):
-        self.SendCommand(Command.RESET, 0, 0, 0, 0)
+        print("Display reset...")
+        # Reset command bypasses queue because it is run when queue threads are not yet started
+        self.SendCommand(Command.RESET, 0, 0, 0, 0, bypass_queue=True)
+        # Wait for display reset then reconnect
+        time.sleep(1)
+        self.openSerial()
 
     def Clear(self):
+        self.SetOrientation(Orientation.PORTRAIT)  # Bug: orientation needs to be PORTRAIT before clearing
         self.SendCommand(Command.CLEAR, 0, 0, 0, 0)
+        self.SetOrientation()  # Restore default orientation
 
     def ScreenOff(self):
         self.SendCommand(Command.SCREEN_OFF, 0, 0, 0, 0)

library/lcd_comm_rev_b.py

@@ -1,6 +1,5 @@
 import struct
 
-import serial
 from serial.tools.list_ports import comports
 
 from library.lcd_comm import *
@@ -28,15 +27,13 @@ def get_rev_b_orientation(orientation: Orientation) -> OrientationValueRevB:
 
 class LcdCommRevB(LcdComm):
     def __init__(self):
-        self.lcd_serial = None
-        if CONFIG_DATA['config']['COM_PORT'] == 'AUTO':
-            lcd_com_port = self.auto_detect_com_port()
-            self.lcd_serial = serial.Serial(lcd_com_port, 115200, timeout=1, rtscts=1)
-            print(f"Auto detected comm port: {lcd_com_port}")
-        else:
-            lcd_com_port = CONFIG_DATA["config"]["COM_PORT"]
-            print(f"Static comm port: {lcd_com_port}")
-            self.lcd_serial = serial.Serial(lcd_com_port, 115200, timeout=1, rtscts=1)
+        self.openSerial()
+
+    def __del__(self):
+        try:
+            self.lcd_serial.close()
+        except:
+            pass
 
     @staticmethod
     def auto_detect_com_port():
@@ -49,7 +46,7 @@ def auto_detect_com_port():
 
         return auto_com_port
 
-    def SendCommand(self, cmd: Command, payload=None):
+    def SendCommand(self, cmd: Command, payload=None, bypass_queue: bool = False):
         # New protocol (10 byte packets, framed with the command, 8 data bytes inside)
         if payload is None:
             payload = [0] * 8
@@ -68,9 +65,12 @@ def SendCommand(self, cmd: Command, payload=None):
         byteBuffer[8] = payload[7]
         byteBuffer[9] = cmd
 
-        # Lock queue mutex then queue the request
-        with config.update_queue_mutex:
-            config.update_queue.put((self.WriteData, [byteBuffer]))
+        if bypass_queue:
+            self.WriteData(byteBuffer)
+        else:
+            # Lock queue mutex then queue the request
+            with config.update_queue_mutex:
+                config.update_queue.put((self.WriteData, [byteBuffer]))
 
     def WriteData(self, byteBuffer: bytearray):
         try:
@@ -90,28 +90,17 @@ def WriteLine(self, line: bytes):
             print("(Write line) Too fast! Slow down!")
 
     def Hello(self):
-        # This command reads LCD answer on serial link, so it bypasses the queue
-        byteBuffer = bytearray(10)
-        byteBuffer[0] = Command.HELLO
-        byteBuffer[1] = ord('H')
-        byteBuffer[2] = ord('E')
-        byteBuffer[3] = ord('L')
-        byteBuffer[4] = ord('L')
-        byteBuffer[5] = ord('O')
-        byteBuffer[6] = 0
-        byteBuffer[7] = 0
-        byteBuffer[8] = 0
-        byteBuffer[9] = Command.HELLO
+        hello = [ord('H'), ord('E'), ord('L'), ord('L'), ord('O')]
 
-        with config.update_queue_mutex:
-            self.WriteData(byteBuffer)
-            response = self.lcd_serial.read(10)
+        # This command reads LCD answer on serial link, so it bypasses the queue
+        self.SendCommand(Command.HELLO, payload=hello, bypass_queue=True)
+        response = self.lcd_serial.read(10)
 
         if len(response) != 10:
             print("Device not recognised (short response to HELLO)")
         if response[0] != Command.HELLO or response[-1] != Command.HELLO:
             print("Device not recognised (bad framing)")
-        if [x for x in response[1:6]] != byteBuffer[1:6]:
+        if [x for x in response[1:6]] != hello:
             print("Device not recognised (No HELLO; got %r)" % (response[1:6],))
         # The HELLO response here is followed by:
         #   0x0A, 0x12, 0x00
@@ -125,11 +114,13 @@ def InitializeComm(self):
         self.Hello()
 
     def Reset(self):
-        # HW revision B does not implement a command to reset it
-        pass
+        # HW revision B does not implement a command to reset it: clear the screen instead
+        self.Clear()
 
     def Clear(self):
-        pass
+        # HW revision B does not implement a Clear command: display a blank image on the whole screen
+        blank = Image.new("RGB", (get_width(), get_height()), (255, 255, 255))
+        self.DisplayPILImage(blank)
 
     def ScreenOff(self):
         # HW revision B does not implement a "ScreenOff" native command: using SetBrightness(0) instead

library/scheduler.py

@@ -9,6 +9,8 @@
 
 THEME_DATA = config.THEME_DATA
 
+STOPPING = False
+
 
 def async_job(threadname=None):
     """ wrapper to handle asynchronous threads """
@@ -36,8 +38,11 @@ def decorator(func):
 
         def periodic(scheduler, periodic_interval, action, actionargs=()):
             """ Wrap the scheduler with our periodic interval """
-            scheduler.enter(periodic_interval, 1, periodic,
-                            (scheduler, periodic_interval, action, actionargs))
+            global STOPPING
+            if not STOPPING:
+                # If the program is not stopping: re-schedule the task for future execution
+                scheduler.enter(periodic_interval, 1, periodic,
+                                (scheduler, periodic_interval, action, actionargs))
             action(*actionargs)
 
         @wraps(func)
@@ -120,6 +125,19 @@ def DiskStats():
 @async_job("Queue_Handler")
 @schedule(timedelta(milliseconds=1).total_seconds())
 def QueueHandler():
-    f, args = config.update_queue.get()
-    if f:
-        f(*args)
+    global STOPPING
+
+    if STOPPING:
+        # Empty the message queue to allow program to exit cleanly
+        while not config.update_queue.empty():
+            f, args = config.update_queue.get()
+            f(*args)
+    else:
+        # Execute first action in the queue
+        f, args = config.update_queue.get()
+        if f:
+            f(*args)
+
+
+def is_queue_empty() -> bool:
+    return config.update_queue.empty()

main.py

@@ -5,6 +5,7 @@
 import os
 import signal
 import sys
+import time
 
 MIN_PYTHON = (3, 7)
 if sys.version_info < MIN_PYTHON:
@@ -20,12 +21,27 @@
 if __name__ == "__main__":
 
     def sighandler(signum, frame):
-        print(" Caught signal ", str(signum), ", exiting...")
+        print(" Caught signal ", str(signum), ", exiting")
+
+        # Do not stop the program now in case data transmission was in progress
+        # Instead, ask the scheduler to finish its current task before stopping
+        scheduler.STOPPING = True
+
+        print("Waiting for all pending request to be sent to display...")
+
+        # Allow 2 seconds max. delay in case scheduler is not responding
+        wait_time = 2
+        while not scheduler.is_queue_empty() and wait_time > 0:
+            time.sleep(0.1)
+            wait_time = wait_time - 0.1
+
+        # We force the exit to avoid waiting for other scheduled tasks: they may have a long delay!
         try:
             sys.exit(0)
         except:
             os._exit(0)
 
+
     # Set the signal handlers, to send a complete frame to the LCD before exit
     signal.signal(signal.SIGINT, sighandler)
     signal.signal(signal.SIGTERM, sighandler)