Scrolling the Adafruit 16×2 LCD+Keypad
I wanted to add additional functionality to my Raspberry FM project by having any long station names \ song names scroll on the Adafruit 16×2 LCD+keypad for Raspberry Pi: While the lcd Python module Adafruit provides has methods to scroll the text (scrollDisplayLeft, scrollDisplayRight, autoScroll), I was unable to get them to work nor find any good examples. Maybe it’s completely possible with what they provide, but I had no luck with it. If anyone does know how, please comment! 
Why not write my own? That’s a fun thing to do on a Saturday afternoon, right? 😉 Find a snapshot of the Python source below, and a link to the most current version on Bitbucket here: lcdScroll.py
To see it in action:
It’s a standalone module I designed to work with any sized lcd: It’s really just a text formatter: All the drawing to the LCD would be handled by some other application. A very simple example can also be found on Bitbucket here: lcdScrollTest.py Or of course you could check out the Raspberry FM source here: raspberryFm01.py
For either the top or bottom line, if they are longer than 16 characters (which is completely adjustable based on the type of lcd used), they will auto-scroll. If less than 16 characters, no scrolling happens. So you can have completely independent scrolling on any line based on their length.
#!/usr/bin/python
"""
lcdScroll.py
Author : Eric Pavey
Creation Date : 2014-02-08
Blog : http://www.akeric.com/blog
Free and open for all to use. But put credit where credit is due.
OVERVIEW:-----------------------------------------------------------------------
Create scrolling text on a LCD display. Designed to work on the the
Adafruit LCD + keypad, but it's not tied to any specific hardware, and should
work on a LCD of any size.
See lcdScrollTest.py for simple example usage.
"""
class Scroller(object):
"""
Object designed to auto-scroll text on a LCD screen. Every time the scroll()
method is called to, it will scroll the text from right to left by one character
on any line that is greater than the provided with.
If the lines ever need to be reset \ updated, call to the setLines() method.
"""
def __init__(self, lines=[], space = " :: ", width=16, height=2):
"""
Instance a LCD scroller object.
Parameters:
lines : list / string : Default empty list : If a list is passed in, each
entry in the list is a string that should be displayed on the LCD,
one line after the next. If a string, it will be split by any embedded
linefeed \n characers into a list of multiple lines .
Ultimately, the number of entries in this list must be equal to or
less than the height argument.
space : string : Default " :: " : If a given line is longer than the width
argument, this string will be added to the end to help designate the
end of the line has been hit during the scroll.
width : int : Default 16 : The width of the LCD display, number of columns.
height : int : Default 2 : the height of the LCD, number of rows.
"""
self.width = width
self.height = height
self.space = space
self.setLines(lines)
def setLines(self, lines):
"""
Set (for the first time) or reset (at any time) the lines to display.
Sets self.lines
Parameters:
lines : list : Each entry in the list is a string
that should be displayed on the LCD, one line after the next. The
number of entries in this list must be equal to or less than the
height argument.
"""
# Just in case a string is passed in, turn it into a list, and split
# by any linefeed chars:
if isinstance(lines, basestring):
lines = lines.split("\n")
elif not isinstance(lines, list):
raise Exception("Argument passed to lines parameter must be list, instead got: %s"%type(lines))
if len(lines) > self.height:
raise Exception("Have more lines to display (%s) than you have lcd rows (%s)"%(len(lines), height))
self.lines = lines
# If the line is over the width, add in the extra spaces to help separate
# the scroll:
for i,ln in enumerate(self.lines[:]):
if len(ln) > self.width:
self.lines[i] = "%s%s"%(ln,self.space)
def scroll(self):
"""
Scroll the text by one character from right to left each time this is
called to.
Return : string : The message to display to the LCD. Each line is separated
by the \n (linefeed) character that the Adafruit LCD expects. Each line
will also be clipped to self.width, so as to not confuse the LCD when
later drawn.
"""
for i,ln in enumerate(self.lines[:]):
if len(ln) > 16:
shift = "%s%s"%(ln[1:], ln[0])
self.lines[i] = shift
truncated = [ln[:self.width] for ln in self.lines]
return "\n".join(truncated)
