refs #5 - use blocking reads instead of polling with sleeps to save CPU cycles

Author: haklein

certabo/serialreader.py

@@ -54,10 +54,13 @@ def __init__ (self, handler, device='auto'):
         self.device = device
         self.connected = False
         self.handler = handler
-        self.serial_out = queue.Queue()
+        self.uart = None
 
     def send_led(self, message: bytes):
-        self.serial_out.put(message)
+        # logging.debug(f'Sending to serial: {message}')
+        if self.connected:
+            return self.uart.write(message)
+        return None
 
     def run(self):
         while True:
@@ -73,27 +76,28 @@ def run(self):
                         time.sleep(1)
                         continue
                     logging.info(f'Opening serial port {serialport}')
-                    uart = serial.Serial(serialport, 38400, timeout=2.5)  # 0-COM1, 1-COM2 / speed /
+                    self.uart = serial.Serial(serialport, 38400)  # 0-COM1, 1-COM2 / speed /
+                    # self.uart = serial.Serial(serialport, 38400, timeout=2.5)  # 0-COM1, 1-COM2 / speed /
                     if os.name == 'posix':
                         logging.debug(f'Attempting to lock {serialport}')
-                        fcntl.flock(uart.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
+                        fcntl.flock(self.uart.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
                     logging.debug(f'Flushing input on {serialport}')
-                    uart.flushInput()
-                    uart.write(b'U\xaaU\xaaU\xaaU\xaa')
+                    self.uart.flushInput()
+                    self.uart.write(b'U\xaaU\xaaU\xaaU\xaa')
                     time.sleep(1)
-                    uart.write(b'\xaaU\xaaU\xaaU\xaaU')
+                    self.uart.write(b'\xaaU\xaaU\xaaU\xaaU')
                     time.sleep(1)
-                    uart.write(b'\x00\x00\x00\x00\x00\x00\x00\x00')
+                    self.uart.write(b'\x00\x00\x00\x00\x00\x00\x00\x00')
                     self.connected = True
                 except Exception as e:
                     logging.info(f'ERROR: Cannot open serial port {serialport}: {str(e)}')
                     self.connected = False
                     time.sleep(0.1)
             else:
                 try:
-                    while uart.inWaiting():
+                    while True:
                         # logging.debug(f'serial data pending')
-                        raw_message = uart.readline()
+                        raw_message = self.uart.readline()
                         try:
                             message = raw_message.decode("ascii")[1: -3]
                             #if DEBUG:
@@ -103,12 +107,6 @@ def run(self):
                             message = ""
                         except Exception as e:
                             logging.info(f'Exception during message decode: {str(e)}')
-                    time.sleep(0.001)
-                    if not self.serial_out.empty():
-                        data = self.serial_out.get()
-                        self.serial_out.task_done()
-                        # logging.debug(f'Sending to serial: {data}')
-                        uart.write(data)
                 except Exception as e:
                     logging.info(f'Exception during serial communication: {str(e)}')
                     self.connected = False