Todbot's Displays Tricks
displayio is the native system-level driver for displays in CircuitPython. Several CircuitPython boards (FunHouse, MagTag, PyGamer, CLUE) have displayio-based displays and a built-in board.DISPLAY object that is preconfigured for that display. Or, you can add your own I2C or SPI display.
Get default display and change display rotation
Boards like FunHouse, MagTag, PyGamer, CLUE have built-in displays. display.rotation works with all displays, not just built-in ones.
import board display = board.DISPLAY print(display.rotation) # print current rotation display.rotation = 0 # valid values 0,90,180,270
Display an Image
The adafruit_imageload library makes it easier to load images and display them. The images should be in palettized BMP3 format.
import board import displayio import adafruit_imageload img_filename = "bg_jp200.bmp" display = board.DISPLAY img, pal = adafruit_imageload.load(img_filename) group = displayio.Group() group.append(displayio.TileGrid(img, pixel_shader=pal)) display.root_group = group
CircuitPython's displayio library works like:
- an image
Bitmapgoes inside aTileGrid - a
TileGridgoes inside aGroup - the
Groupis set to be the root group on aDisplay.
Display Background Bitmap
Useful for display a solid background color that can be quickly changed.
import time, board, displayio display = board.DISPLAY # get default display (FunHouse,Pygamer,etc) maingroup = displayio.Group() # Create a main group to hold everything display.root_group = maingroup # put it on the display # make bitmap that spans entire display, with 3 colors background = displayio.Bitmap(display.width, display.height, 3) # make a 3 color palette to match mypal = displayio.Palette(3) mypal[0] = 0x000000 # set colors (black) mypal[1] = 0x999900 # dark yellow mypal[2] = 0x009999 # dark cyan # Put background into main group, using palette to map palette ids to colors maingroup.append(displayio.TileGrid(background, pixel_shader=mypal)) time.sleep(2) background.fill(2) # change background to dark cyan (mypal[2]) time.sleep(2) background.fill(1) # change background to dark yellow (mypal[1])
Another way is to use vectorio:
import board, displayio, vectorio
display = board.DISPLAY # built-in display
maingroup = displayio.Group() # a main group that holds everything
display.root_group = maingroup
mypal = displayio.Palette(1)
mypal[0] = 0x999900
background = vectorio.Rectangle(
pixel_shader=mypal,
width=display.width,
height=display.height,
x=0,
y=0,
)
maingroup.append(background)
Or can also use adafruit_display_shapes:
import board, displayio from adafruit_display_shapes.rect import Rect display = board.DISPLAY maingroup = displayio.Group() # a main group that holds everything display.root_group = maingroup # add main group to display background = Rect(0,0, display.width, display.height, fill=0x000000 ) # background color maingroup.append(background)
import time, board, displayio
import adafruit_imageload
display = board.DISPLAY # get display object (built-in on some boards)
screen = displayio.Group() # main group that holds all on-screen content
display.root_group = screen # add it to display
file_names = [ '/images/cat1.bmp', '/images/cat2.bmp' ] # list of filenames
screen.append(displayio.Group()) # placeholder, will be replaced w/ screen[0] below
while True:
for fname in file_names:
image, palette = adafruit_imageload.load(fname)
screen[0] = displayio.TileGrid(image, pixel_shader=palette)
time.sleep(1)
Note: Images must be in palettized BMP3 format. For more details, see Preparing images for CircuitPython
Dealing with E-Ink "Refresh Too Soon" Error
E-Ink displays are damaged if refreshed too frequently. CircuitPython enforces this, but also provides display.time_to_refresh, the number of seconds you need to wait before the display can be refreshed. One solution is to sleep a little longer than that and you'll never get the error. Another would be to wait for time_to_refresh to go to zero, as shown below.
import time, board, displayio, terminalio
from adafruit_display_text import label
mylabel = label.Label(terminalio.FONT, text="demo", x=20,y=20,
background_color=0x000000, color=0xffffff )
display = board.DISPLAY # e.g. for MagTag
display.root_group = mylabel
while True:
if display.time_to_refresh == 0:
display.refresh()
mylabel.text = str(time.monotonic())
time.sleep(0.1)
Page last edited March 23, 2024
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