Move wait implementation to base class, make sleep amount tune-able

Remove busy-wait
Fix initialization bug

Author: Tomáš Jozífek

RPLCD/gpio.py

@@ -30,12 +30,6 @@
 from .lcd import BaseCharLCD
 from .compat import range
 
-import sys
-if sys.version_info.major < 3:
-    from time import clock as now
-else:
-    from time import perf_counter as now
-
 PinConfig = namedtuple('PinConfig', 'rs rw e d0 d1 d2 d3 d4 d5 d6 d7 backlight mode')
 
 
@@ -46,7 +40,8 @@ def __init__(self, numbering_mode=None, pin_rs=None, pin_rw=None, pin_e=None, pi
                        cols=20, rows=4, dotsize=8,
                        charmap='A02',
                        auto_linebreaks=True,
-                       compat_mode=False):
+                       compat_mode=False,
+                       compat_mode_wait_time=0.001):
         """
         Character LCD controller.
 
@@ -94,6 +89,9 @@ def __init__(self, numbering_mode=None, pin_rs=None, pin_rw=None, pin_e=None, pi
         :param compat_mode: Whether to run additional checks to support older LCDs
             that may not run at the reference clock (or keep up with it).
         :type compat_mode: bool
+        :param compat_mode_wait_time: Minimum time to pass between sends.
+            if zero, turns off compat_mode  Default: ``0.001`` seconds.
+        :type compat_mode_wait_time: float
 
         """
 
@@ -130,7 +128,8 @@ def __init__(self, numbering_mode=None, pin_rs=None, pin_rw=None, pin_e=None, pi
         super(CharLCD, self).__init__(cols, rows, dotsize,
                                       charmap=charmap,
                                       auto_linebreaks=auto_linebreaks,
-                                      compat_mode=compat_mode)
+                                      compat_mode=compat_mode,
+                                      compat_mode_wait_time=compat_mode_wait_time)
 
         # Set backlight status
         if pin_backlight is not None:
@@ -184,9 +183,8 @@ def _set_backlight_enabled(self, value):
     def _send(self, value, mode):
         """Send the specified value to the display with automatic 4bit / 8bit
         selection. The rs_mode is either ``RS_DATA`` or ``RS_INSTRUCTION``."""
-        # Wait, if compatibility mode is enabled
-        if self.compat_mode:
-            self._wait()
+        # Wait if compatibility mode is enabled
+        self._compat_mode_wait()
 
         # Choose instruction or data mode
         GPIO.output(self.pins.rs, mode)
@@ -203,8 +201,7 @@ def _send(self, value, mode):
             self._write4bits(value)
 
         # Record the time for the tail-end of the last send event
-        if self.compat_mode:
-            self.last_send_event = now()
+        self._compat_mode_record_send_event()
 
     def _send_data(self, value):
         """Send data to the display. """
@@ -237,4 +234,3 @@ def _pulse_enable(self):
         GPIO.output(self.pins.e, 0)
         c.usleep(100)  # commands need > 37us to settle
 
-

RPLCD/lcd.py

@@ -32,9 +32,7 @@
     from time import clock as now
 else:
     from time import perf_counter as now
-
-# Duration to rate-limit calls to _send
-COMPAT_MODE_WAIT_TIME = 0.001
+from time import sleep
 
 LCDConfig = namedtuple('LCDConfig', 'rows cols dotsize')
 
@@ -45,7 +43,8 @@ class BaseCharLCD(object):
 
     # Init, setup, teardown
 
-    def __init__(self, cols=20, rows=4, dotsize=8, charmap='A02', auto_linebreaks=True, compat_mode=False):
+    def __init__(self, cols=20, rows=4, dotsize=8, charmap='A02', auto_linebreaks=True, compat_mode=False,
+                 compat_mode_wait_time=0.001):
         """
         Character LCD controller. Base class only, you should use a subclass.
 
@@ -63,10 +62,21 @@ def __init__(self, cols=20, rows=4, dotsize=8, charmap='A02', auto_linebreaks=Tr
             auto_linebreaks:
                 Whether or not to automatically insert line breaks.
                 Default: True.
-
+            compat_mode:
+                Whether to run additional checks to support older LCDs
+                that may not run at the reference clock (or keep up with it).
+                Default: False
+            compat_mode_wait_time: Minimum time to pass between sends.
+                if zero, turns off compat_mode
+                Default: ``0.001`` seconds.
         """
         assert dotsize in [8, 10], 'The ``dotsize`` argument should be either 8 or 10.'
 
+        # Configure compatibility mode
+        self.compat_mode = compat_mode and compat_mode_wait_time > 0
+        self.compat_mode_wait_time = compat_mode_wait_time
+        self._compat_mode_record_send_event()
+
         # Initialize codec
         if charmap == 'A00':
             self.codec = codecs.A00Codec()
@@ -124,8 +134,6 @@ def __init__(self, cols=20, rows=4, dotsize=8, charmap='A02', auto_linebreaks=Tr
         else:
             raise ValueError('Invalid data bus mode: {}'.format(self.data_bus_mode))
 
-
-
         # Write configuration to display
         self.command(c.LCD_FUNCTIONSET | displayfunction)
         c.usleep(50)
@@ -146,11 +154,6 @@ def __init__(self, cols=20, rows=4, dotsize=8, charmap='A02', auto_linebreaks=Tr
         self.command(c.LCD_ENTRYMODESET | self._text_align_mode | self._display_shift_mode)
         c.usleep(50)
 
-        # Configure compatibility mode
-        self.compat_mode = compat_mode
-        if compat_mode:
-            self.last_send_event = now()
-
     def close(self, clear=False):
         if clear:
             self.clear()
@@ -253,12 +256,6 @@ def _set_cursor_mode(self, value):
     cursor_mode = property(_get_cursor_mode, _set_cursor_mode,
             doc='How the cursor should behave (``hide``, ``line`` or ``blink``).')
 
-    def _wait(self):
-        """Rate limit the number of send events."""
-        end = self.last_send_event + COMPAT_MODE_WAIT_TIME
-        while now() < end:
-            pass
-
     # High level commands
 
     def write_string(self, value):
@@ -467,3 +464,19 @@ def crlf(self):  # type: () -> None
         """Write a line feed and a carriage return (``\\r\\n``) character to the LCD."""
         self.write_string('\r\n')
 
+    def _is_compat_mode_on(self):
+        """Compat mode is on, when it's enabled and the wait time is > 0"""
+        return self.compat_mode and self.compat_mode_wait_time > 0
+
+    def _compat_mode_wait(self):
+        """Wait the specified amount, if the compat mode is on, to rate limit the data transmission"""
+        if self._is_compat_mode_on():
+            end = self.last_send_event + self.compat_mode_wait_time
+            sleep_duration = end - now()
+            if sleep_duration > 0:
+                sleep(sleep_duration)
+
+    def _compat_mode_record_send_event(self):
+        """Record when did the last send take place, so the rate limiting adapts to any slowdowns."""
+        self.last_send_event = now()
+

RPLCD/pigpio.py

@@ -31,12 +31,6 @@
 from .lcd import BaseCharLCD
 from .compat import range
 
-import sys
-if sys.version_info.major < 3:
-    from time import clock as now
-else:
-    from time import perf_counter as now
-
 # https://diarmuid.ie/blog/pwm-exponential-led-fading-on-arduino-or-other-platforms/
 # p 101 .. maximum value of the PWM cycle
 # m 100 .. number of steps the LED will fade over
@@ -58,7 +52,8 @@ def __init__(self, pi,
                        cols=20, rows=4, dotsize=8,
                        charmap='A02',
                        auto_linebreaks=True,
-                       compat_mode=False):
+                       compat_mode=False,
+                       compat_mode_wait_time=0.001):
         """
         Character LCD controller.
 
@@ -124,6 +119,9 @@ def __init__(self, pi,
         :param auto_linebreaks: Whether or not to automatically insert line
             breaks. Default: ``True``.
         :type auto_linebreaks: bool
+        :param compat_mode_wait_time: Minimum time to pass between sends.
+            if zero, turns off compat_mode  Default: ``0.001`` seconds.
+        :type compat_mode_wait_time: float
 
         """
 
@@ -158,7 +156,8 @@ def __init__(self, pi,
         super(CharLCD, self).__init__(cols, rows, dotsize,
                                       charmap=charmap,
                                       auto_linebreaks=auto_linebreaks,
-                                      compat_mode=compat_mode)
+                                      compat_mode=compat_mode,
+                                      compat_mode_wait_time=compat_mode_wait_time)
 
         # Set backlight status
         if pin_backlight is not None:
@@ -308,8 +307,7 @@ def _send(self, value, mode):
         selection. The rs_mode is either ``RS_DATA`` or ``RS_INSTRUCTION``."""
 
         # Wait, if compatibility mode is enabled
-        if self.compat_mode:
-            self._wait()
+        self._compat_mode_wait()
 
         # Assemble the parameters sent to the pigpio script
         params = [mode]
@@ -328,8 +326,7 @@ def _send(self, value, mode):
         pigpio.exceptions = True
 
         # Record the time for the tail-end of the last send event
-        if self.compat_mode:
-            self.last_send_event = now()
+        self._compat_mode_record_send_event()
 
     def _send_data(self, value):
         """Send data to the display. """