Runtime warning

[vitasam]

Hello,

I have got this code working, why such warning appeared?

pi@raspberrypi:~/PythonStuff/LCD16x2 $ sudo python rplcd.py
/usr/local/lib/python2.7/dist-packages/RPLCD/lcd.py:191: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(pin, GPIO.OUT)

[dbrgn]

It means that either there's another program running that uses the same GPIO pin, or that the GPIO pin has not been properly closed by a program that used the pin in the past (with GPIO.cleanup()).

Searching for "this channel is already in use" should yield more results: https://duckduckgo.com/?q=%22This+channel+is+already+in+use%22&ia=web

Please comment again if this issue is not resolved for you :)

[vitasam]

Hi, I did reboot the Raspberry - there should not be any program that used the same GPIO, isn't it? I've rebooted the PC and did try to use GPIO.cleanup() in the following code:

from RPLCD import CharLCD
import RPi.GPIO as GPIO

GPIO.cleanup()

lcd = CharLCD()
lcd.write_string(u'Raspberry Pi HD44780')

GPIO.cleanup()

Apparently it did not help:

pi@raspberrypi:~/PythonStuff/LCD16x2 $ sudo python rplcd.py
rplcd.py:4: RuntimeWarning: No channels have been set up yet - nothing to clean up!  Try cleaning up at the end of your program instead!
  GPIO.cleanup()
/usr/local/lib/python2.7/dist-packages/RPLCD/lcd.py:191: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(pin, GPIO.OUT)

[dbrgn]

I'm not sure. Is the Raspbian installation fresh? Are there other processes running that might access GPIO?

[vitasam]

Hi, Raspbian installation was pretty much fresh. And it works Ok e.g. with this script: http://www.raspberrypi-spy.co.uk/2012/08/16x2-lcd-module-control-with-backlight-switch/#comment-192164

[dbrgn]

Does it only happen the second time you run the script? Do you call lcd.close() afterwards?

[vitasam]

Actually I did not call lcd.close() WIll try. Thanks!

[dbrgn]

Let me know if it helps!

[vitasam]

Yes, sure!

[vitasam]

Hi,

Thanks! lcd.close() did help with warnings, following code was running Ok (including one API pin assignment):

pi@raspberrypi:~ $ cat PythonStuff/LCD16x2/rplcd_test.py
from RPLCD import CharLCD
import RPi.GPIO as GPIO

lcd = CharLCD(pin_rs=13)
lcd.write_string(u'Raspberry Pi HD44780')

lcd.close()
pi@raspberrypi:~ $ sudo python PythonStuff/LCD16x2/rplcd_test.py
pi@raspberrypi:~ $

There is some problem with Backlight. I did try this Init, Setup, Teardown example, but got an error:

pi@raspberrypi:~ $ sudo python PythonStuff/LCD16x2/rplcd_test.py
Traceback (most recent call last):
  File "PythonStuff/LCD16x2/rplcd_test.py", line 2, in <module>
    from RPLCD import CharLCD, BacklightMode
ImportError: cannot import name BacklightMode

[dbrgn]

Looks like that version wasn't deployed yet.

I just pushed version 0.4.0 to PyPI, can you try with that?

Also, if your project is public, it would be cool if you could send me a link :) Then I could start a list of hardware projects using RPLCD.

[vitasam]

Hi, it works now, after I did an update:

pi@raspberrypi:~ $ cat PythonStuff/LCD16x2/rplcd_test.py
from RPLCD import CharLCD, BacklightMode
import time

lcd = CharLCD(pin_rs=13, pin_backlight=10, backlight_enabled=True, backlight_mode=BacklightMode.active_high)
lcd.write_string(u'Raspberry Pi HD44780')
lcd.backlight = True
time.sleep(2)
lcd.backlight = False
lcd.close()

I just started an open project but it was without your library. I will update the project to RPLCD and will send you a link :)

Is it Ok if my project under GPL v 3 license and your code is under MIT?

[dbrgn]

Yes, MIT licensed code may be included in GPL licensed projects :)

Great that it works now.

[vitasam]

Ok, good! By the way what is a best way to map that LCD in to RaspPi? From the GPIO utilization point of view (e.g. to not to occupy SPI bus etc.)?

[dbrgn]

Do you mean the pin usage? Simply make sure that you don't use the SPI pins. You can give any pin mapping to the constructor of the CharLCD class.

[vitasam]

Hi, this is my PreAlpha project, where I've migrated to RPLCD library: https://sourceforge.net/projects/home-controller/

Now display works much more stable :)