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Attempt to fix compat_mode_pigpio #115

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93e8a43
-move compat mode to base
makslevental Apr 2, 2019
61ed40b
Move wait implementation to base class, make sleep amount tune-able
May 5, 2020
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36 changes: 11 additions & 25 deletions RPLCD/gpio.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,15 +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

# Duration to rate-limit calls to _send
COMPAT_MODE_WAIT_TIME = 0.001

PinConfig = namedtuple('PinConfig', 'rs rw e d0 d1 d2 d3 d4 d5 d6 d7 backlight mode')


Expand All @@ -49,7 +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.

Expand Down Expand Up @@ -97,12 +89,11 @@ 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

"""
# Configure compatibility mode
self.compat_mode = compat_mode
if compat_mode:
self.last_send_event = now()

# Set attributes
if numbering_mode == GPIO.BCM or numbering_mode == GPIO.BOARD:
Expand Down Expand Up @@ -136,7 +127,9 @@ def __init__(self, numbering_mode=None, pin_rs=None, pin_rw=None, pin_e=None, pi
# Call superclass
super(CharLCD, self).__init__(cols, rows, dotsize,
charmap=charmap,
auto_linebreaks=auto_linebreaks)
auto_linebreaks=auto_linebreaks,
compat_mode=compat_mode,
compat_mode_wait_time=compat_mode_wait_time)

# Set backlight status
if pin_backlight is not None:
Expand Down Expand Up @@ -190,9 +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)
Expand All @@ -209,8 +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. """
Expand Down Expand Up @@ -243,8 +234,3 @@ def _pulse_enable(self):
GPIO.output(self.pins.e, 0)
c.usleep(100) # commands need > 37us to settle

def _wait(self):
"""Rate limit the number of send events."""
end = self.last_send_event + COMPAT_MODE_WAIT_TIME
while now() < end:
pass
40 changes: 37 additions & 3 deletions RPLCD/lcd.py
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,12 @@
from . import codecs
from . import common as c
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
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@dbrgn dbrgn Oct 3, 2021

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Looking at this Python 2 compat code, I think it's time to drop Python 2 support in the next release. However, for now, let's keep it since it still works.

from time import sleep

LCDConfig = namedtuple('LCDConfig', 'rows cols dotsize')

Expand All @@ -38,7 +43,8 @@ class BaseCharLCD(object):

# Init, setup, teardown

def __init__(self, cols=20, rows=4, dotsize=8, charmap='A02', auto_linebreaks=True):
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.

Expand All @@ -56,10 +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.
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@dbrgn dbrgn Oct 3, 2021

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Since compat_mode=False and compat_mode_wait_time=0 are essentially the same, can we merge the two parameters?

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@TojikCZ TojikCZ Oct 4, 2021

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Yes, I'd like to. But there are two problems with having just the wait amount.
We'll lose backwards compatibility. That's ok. I can do an assert that tells would be users what to do instead.
There would be no default for compat_mode "on". The default amount would have to be sourced from something like DEFAULT_COMPAT_WAIT_TIME constant or the docs.
It's undoubtedly cleaner and gets rid of invalid configs like compat_mode=False with a high compat_mode_wait_time value. Your pick 😉

"""
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()
Expand Down Expand Up @@ -446,3 +463,20 @@ def lf(self): # type: () -> None
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()

18 changes: 15 additions & 3 deletions RPLCD/pigpio.py
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,6 @@
from .lcd import BaseCharLCD
from .compat import range


# 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
Expand All @@ -52,7 +51,9 @@ def __init__(self, pi,
contrast_pwm=None, contrast=0.5,
cols=20, rows=4, dotsize=8,
charmap='A02',
auto_linebreaks=True):
auto_linebreaks=True,
compat_mode=False,
compat_mode_wait_time=0.001):
"""
Character LCD controller.

Expand Down Expand Up @@ -118,6 +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

"""

Expand Down Expand Up @@ -151,7 +155,9 @@ def __init__(self, pi,
# Call superclass
super(CharLCD, self).__init__(cols, rows, dotsize,
charmap=charmap,
auto_linebreaks=auto_linebreaks)
auto_linebreaks=auto_linebreaks,
compat_mode=compat_mode,
compat_mode_wait_time=compat_mode_wait_time)

# Set backlight status
if pin_backlight is not None:
Expand Down Expand Up @@ -300,6 +306,9 @@ 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
self._compat_mode_wait()

# Assemble the parameters sent to the pigpio script
params = [mode]
params.extend([(value >> i) & 0x01 for i in range(8)])
Expand All @@ -316,6 +325,9 @@ def _send(self, value, mode):
# Switch on pigpio's exceptions
pigpio.exceptions = True

# Record the time for the tail-end of the last send event
self._compat_mode_record_send_event()

def _send_data(self, value):
"""Send data to the display. """
self._send(value, c.RS_DATA)
Expand Down