11 KiB
Galactic Unicorn (MicroPython)
Galactic Unicorn offers 53x11 bright RGB LEDs driven by Pico W's PIO in addition to a 1W amplifier + speaker, a collection of system and user buttons, and two Qw/ST connectors for adding external sensors and devices. Woha!
You can buy one here: https://shop.pimoroni.com/products/galactic-unicorn
These are not your everyday RGB LEDs!
Internally Galactic Unicorn applies gamma correction to the supplied image data and updates the display with 14-bit precision resulting in extremely linear visual output - including at the low end.
The display is refreshed around 300 times per second (300fps!) allowing for rock solid stability even when being filmed, no smearing or flickering even when in motion.
No strobing or brightness stepping here folks - it's the perfect backdrop for your tricked out streaming setup!
Getting started
The Galactic Unicorn library provides a collection of methods that allow you to easily access all of the features on the board.
Drawing is primarily handled via our PicoGraphics library which provides a comprehensive selection of drawing methods - once your drawing work is complete you pass the PicoGraphics object to Galactic Unicorn to have it displayed on the screen.
- Example Program
- Interleaved Framebuffer
- Function Reference
Example Program
The following example shows how to scroll a simple message across the display.
from galactic import GalacticUnicorn
from picographics import PicoGraphics, DISPLAY_GALACTIC_UNICORN
import time
# create a PicoGraphics framebuffer to draw into
graphics = PicoGraphics(display=DISPLAY_GALACTIC_UNICORN)
# create our GalacticUnicorn object
gu = GalacticUnicorn()
# start position for scrolling (off the side of the display)
scroll = float(-GalacticUnicorn.WIDTH)
# message to scroll
MESSAGE = "Pirate. Monkey. Robot. Ninja."
# pen colours to draw with
BLACK = graphics.create_pen(0, 0, 0)
YELLOW = graphics.create_pen(255, 255, 0)
while True:
# determine the scroll position of the text
width = graphics.measure_text(MESSAGE, 1)
scroll += 0.25
if scroll > width:
scroll = float(-GalacticUnicorn.WIDTH)
# clear the graphics object
graphics.set_pen(BLACK)
graphics.clear()
# draw the text
graphics.set_pen(YELLOW)
graphics.text(MESSAGE, round(0 - scroll), 2, -1, 0.55);
# update the display
gu.update(graphics)
time.sleep(0.02)
Interleaved Framebuffer
Galactic Unicorn takes advantage of the RP2040's PIOs to drive screen updates - this is what gives it the performance it needs to render with 14-bit precision at over 300 frames per second.
The PIO is a powerful, but limited, tool. It has no way to access memory at random and minimal support for decision making and branching. All it can really do is process a stream of data/instructions in order.
This means that we need to be clever about the way we pass data into the PIO program, the information needs to be delivered in the exact order that the PIO will need to process it. To achieve this we "interleave" our framebuffer - each frame of BCM data is passed one after another with values for the current row, pixel count, and timing inserted as needed:
row 0 data:
for each bcd frame:
bit : data
0: 00110110 // row pixel count (minus one)
1 - 53: xxxxxbgr, xxxxxbgr, xxxxxbgr, ... // pixel data
54 - 55: xxxxxxxx, xxxxxxxx // dummy bytes to dword align
56: xxxxrrrr // row select bits
57 - 59: tttttttt, tttttttt, tttttttt // bcd tick count (0-65536)
row 1 data:
...
If you're working with our library then you don't need to worry about any of these details, they are handled for you.
Function Reference
Imports and Objects
To access these functions, you'll need to first import the relevant libraries and then set up a Galactic Unicorn object:
from galactic import GalacticUnicorn
gu = GalacticUnicorn()
or (with PicoGraphics):
from galactic import GalacticUnicorn
from picographics import PicoGraphics, DISPLAY_GALACTIC_UNICORN
gu = GalacticUnicorn()
graphics = PicoGraphics(display=DISPLAY_GALACTIC_UNICORN)
System State
set_brightness(value)
Set the brightness - value is supplied as a floating point value between 0.0 and 1.0.
get_brightness()
Returns the current brightness as a value between 0.0 and 1.0.
adjust_brightness(delta)
Adjust the brightness of the display - delta is supplied as a floating point value and will be added to the current brightness (and then clamped to the range 0.0 to 1.0).
For example:
gu.set_brightness(0.5)
gu.adjust_brightness(0.1) # brightness is now 0.6
gu.adjust_brightness(0.7) # brightness is now 1.0
gu.adjust_brightness(-0.2) # brightness is now 0.8
set_volume(value)
Set the volume - value is supplied as a floating point value between 0.0 and 1.0.
get_volume()
Returns the current volume as a value between 0.0 and 1.0.
adjust_volume(delta)
Adjust the volume - delta is supplied as a floating point value and will be added to the current volume (and then clamped to the range 0.0 to 1.0).
For example:
gu.set_volume(0.5)
gu.set_volume(0.1) # volume is now 0.6
gu.adjust_volume(0.7) # volume is now 1.0
gu.adjust_volume(-0.2) # volume is now 0.8
light()
Get the current value seen by the onboard light sensor as a value between 0 and 4095.
is_pressed(button)
Returns true if the requested button is currently pressed.
There are a set of constants in the GalacticUnicorn class that represent each of the buttons. The brightness, sleep, and volume buttons are not tied to hardware functions (they are implemented entirely in software) so can also be used for user functions if preferred. Here's a list of the constants and their associated pin numbers:
SWITCH_A = 0
SWITCH_B = 1
SWITCH_C = 3
SWITCH_D = 6
SWITCH_SLEEP = 27
SWITCH_VOLUME_UP = 7
SWITCH_VOLUME_DOWN = 8
SWITCH_BRIGHTNESS_UP = 21
SWITCH_BRIGHTNESS_DOWN = 26
For example:
while not gu.is_pressed(GalacticUnicorn.SWITCH_A):
# wait for switch A to be pressed
pass
print("We did it! We pressed switch A! Heck yeah!")
Drawing
update(PicoGraphics)
The PicoGraphics library provides a collection of powerful drawing methods to make things simple.
The image on the PicoGraphics object provided is copied to the interleaved framebuffer with gamma correction applied.
For example (assuming you've set up your Galactic Unicorn and PicoGraphics objects up as we did above):
gu.update(graphics)
⚠️ If you've used PicoGraphics on our other boards note that this update function works a little differently. Here it's a Galactic Unicorn function to which you need to pass a PicoGraphics object to.
clear()
Clear the contents of the interleaved framebuffer. This will make your Galactic Unicorn display turn off. To show an image again, call the update() function as described above.
Audio
Audio functionality is supported by our PicoSynth library which allows you to create multiple voice channels with ADSR (attack decay sustain release) envelopes. It provides a similar set of functionality to the classic SID chip in the Commodore 64.
play_sample(data)
Play the provided 16-bit audio sample. data must point to a bytearray that contains 16-bit PCM data. The number of samples is retrieved from the array's length.
synth_channel(channel)
Gets a Channel object which can then be configured with voice, ADSR envelope, etc.
play_synth()
Start the synth playing.
stop_playing()
Stops any currently playing audio.
Channel Reference
configure(waveforms=None, frequency=None, volume=None,
attack=None, decay=None, sustain=None,
release=None, pulse_width=None)
restore()
waveforms()
waveforms(waveforms)
frequency()
frequency(frequency)
volume()
volume(volume)
attack_duration()
attack_duration(duration)
decay_duration()
decay_duration(duration)
sustain_level()
sustain_level(level)
release_duration()
release_duration(duration)
pulse_width()
pulse_width(width)
trigger_attack() # start the channel playing
trigger_release() # stop the channel playing
play_tone(frequency, volume=None, attack=None, release=None)
Constants
WIDTH & HEIGHT
The width and height of Galactic Unicorn are available in constants WIDTH and HEIGHT.
For example:
num_pixels = GalacticUnicorn.WIDTH * GalacticUnicorn.HEIGHT
print(num_pixels)
Using Breakouts
Galactic Unicorn has two Qw/ST (Qwiic/STEMMA QT) connectors. Breakouts with Qw/ST connectors, can be plugged straight in with a JST-SH to JST-SH cable. You can connect I2C Breakout Garden breakouts without Qw/ST connectors using a JST-SH to JST-SH cable and a Qw/ST to Breakout Garden adaptor.
Galactic Unicorn uses GP4 and GP5 for its I2C interface. You can use the constants in the shared pimoroni module to set up the I2C interface:
from pimoroni_i2c import PimoroniI2C
from pimoroni import PINS_BREAKOUT_GARDEN
i2c = PimoroniI2C(**PINS_BREAKOUT_GARDEN)
Alternatively, you can specify the pin numbers directly:
from pimoroni_i2c import PimoroniI2C
i2c = PimoroniI2C(sda=4, scl=5)