Broken CPython support about python_lcd

[clach04]

Error details:

Traceback (most recent call last):
  File "my_demo.py", line 40, in <module>
    lcd.custom_char(0, happy_face)
  File "/home/pi/py/python_lcd_clach04/lcd/lcd_api.py", line 170, in custom_char
    self.hal_sleep_us(40)
  File "/home/pi/py/python_lcd_clach04/lcd/lcd_api.py", line 208, in hal_sleep_us
    time.sleep_us(usecs)
AttributeError: module 'time' has no attribute 'sleep_us'

[dhylands]

The intent is that lcd_api.py should be independent of the platform. So it shouldn't have a sleep or a sleep_us in it. sleep_us is used so that you don't need to have floating point enabled (not all micropython port provide support for floating point operations).

Unfortunately, the sleep stuff came in fairly late in the development, so I added a "default" implementation in lcd_api.py so as not to break the existing implementations.

Specific hal layers can override this if desired. circuitpython, for example, also doesn't support sleep_us so it provides a hal_sleep_us function like this:

python_lcd/lcd/circuitpython_i2c_lcd.py

Lines 84 to 86 in 4376476

	def hal_sleep_us(self, usecs):
	"""Sleep for some time (given in microseconds)."""
	sleep(float(usecs)/1e6)

It looks like i2c_lcd.py (which is intended for CPython use) should provide a similar hal_sleep_us function.

[dhylands]

I think that adding some comments to the hal_sleep_us function implemented in lcd_api.py would also help.

[clach04]

Thanks for taking the time to explain this, really helpful. I posted a PR that resolves the issue and should help with other platforms. It may benefit from further comments/hints.