The PCD8544 is driven with python using the implementation in the
luma.lcd.device.pcd8544 class. Likewise, to drive the ST7735 or
UC1701X, use the
luma.lcd.device.uc1701x class respectively. Usage is very simple if
you have ever used Pillow or PIL.
First, import and initialise the device:
from luma.core.interface.serial import spi from luma.core.render import canvas from luma.lcd.device import pcd8544, st7735, uc1701x serial = spi(port=0, device=0, gpio_DC=23, gpio_RST=24) device = pcd8544(serial)
The display device should now be configured for use. Note, all the example code snippets in this section are interchangeable between PCD8544 and ST7735 devices.
uc1701x classes all expose a
display() method which takes an image with
attributes consistent with the capabilities of the device. However, for most
cases, for drawing text and graphics primitives, the canvas class should be
used as follows:
with canvas(device) as draw: draw.rectangle(device.bounding_box, outline="white", fill="black") draw.text((30, 40), "Hello World", fill="red")
luma.core.render.canvas class automatically creates an
PIL.ImageDraw object of the correct dimensions and bit depth suitable
for the device, so you may then call the usual Pillow methods to draw onto the
As soon as the with scope is ended, the resultant image is automatically
flushed to the device’s display memory and the
PIL.ImageDraw object is
Any of the standard
PIL.ImageColor color formats may be used, but
since the PCD8544 LCD is monochrome, only the HTML color names
"white" values should really be used; in
fact, by default, any value other than black is treated as white. The
luma.core.render.canvas object does have a
which if set to True, will convert color drawings to a dithered monochrome
effect (see the 3d_box.py example, below).
with canvas(device, dither=True) as draw: draw.rectangle((10, 10, 30, 30), outline="white", fill="red")
Note that there is no such limitation for the ST7735 device which supports 262K colour RGB images, whereby 24-bit RGB images are downscaled to 18-bit RGB.
Landscape / Portrait Orientation¶
By default the PCD8544, ST7735 and UC1701X displays will all be oriented in
landscape mode (84x48, 160x128 and 128x64 pixels respectively). Should you have
an application that requires the display to be mounted in a portrait aspect,
then add a
rotate=N parameter when creating the device:
from luma.core.interface.serial import spi from luma.core.render import canvas from luma.lcd.device import pcd8544 serial = spi(port=0, device=0, gpio_DC=23, gpio_RST=24) device = pcd8544(serial, rotate=1) # Box and text rendered in portrait mode with canvas(device) as draw: draw.rectangle(device.bounding_box, outline="white", fill="black") draw.text((10, 40), "Hello World", fill="red")
N should be a value of 0, 1, 2 or 3 only, where 0 is no rotation, 1 is rotate 90° clockwise, 2 is 180° rotation and 3 represents 270° rotation.
properties reflect the rotated dimensions rather than the physical dimensions.
from luma.core.virtual import sevensegment from luma.lcd.device import ht1621 device = ht1621() seg = sevensegment(device)
The seg instance now has a
property which may be assigned, and when it does will update all digits
according to the limited alphabet the 7-segment displays support. For example,
assuming there are 2 cascaded modules, we have 16 character available, and so
seg.text = "HELLO"
Rather than updating the whole display buffer, it is possible to update ‘slices’, as per the below example:
seg.text[0:5] = "BYE"
HELLO in the previous example, replacing it with
The usual python idioms for slicing (inserting / replacing / deleteing) can be
used here, but note if inserted text exceeds the underlying buffer size, a
ValueError is raised.
Floating point numbers (or text with ‘.’) are handled slightly differently - the decimal-place is fused in place on the character immediately preceding it. This means that it is technically possible to get more characters displayed than the buffer allows, but only because dots are folded into their host character.
These displays typically require a backlight to illuminate the liquid crystal
luma.lcd.aux.backlight class allows a BCM pin to
be specified to control the backlight through software.