Category: Adafruit

adding a neopixel stick to the stm32 feather

whbeebe

In December 2021 I wrote about bringing up the Adafruit STM32F405 Feather ( /2021/12/12/bringing-up-an-adafruit-stm32f405-feather-express/ ). Since that time I added an external Neopixel Stick from Adafruit ( https://www.adafruit.com/product/2869 ). This is the four “color” version of the stick with red, green, blue and white LEDs on each device. I cleaned up and shortened the code from the last post and got a bit more creative strobing the LEDs. The stick strobes a single LED from end to end, while the on-board LED shows the same color being strobed on the stick. Once again it’s Circuit Python version 7.1.1. Wiring for the stick has the stick’s ground attached to the feather’s GND pin, the stick’s 5V pin attached to the feather’s USB pin, and the feathers DIN (data in) pin attached to the Feather’s D5 pin, and configured in the call to neopixel.NeoPixel(...) (code line 13).

import timeimport boardimport neopixel# For the single neopixel on the feather itself.#sneopixel = neopixel.NeoPixel(board.NEOPIXEL, 1, brightness=0.2, auto_write=False, pixel_order=neopixel.GRB)# For the eight neopixel board attached to the feather.#pixelboard = neopixel.NeoPixel(board.D5, 8, brightness=0.2, auto_write=True, pixel_order=neopixel.GRBW)def cycleColor(color):sneopixel.fill(color)sneopixel.show()for i in range(len(pixelboard)):pixelboard[i-1] = (0,0,0,0) # turn LED offpixelboard[i] = colorpixelboard.show()time.sleep(.05)while True:cycleColor((64,0,0,0)) # redcycleColor((0,64,0,0)) # greencycleColor((0,0,64,0)) # bluecycleColor((64,16,0,0)) # orangecycleColor((0,32,32,0)) # cyancycleColor((0,0,0,0)) # black (LED off)

The video was produced on my iPhone 11 Pro with Apple’s iMovie. I know it’s crap as in it won’t earn any awards unless there’s a special Raspberry for iPhone clips, but I didn’t feel like firing up one of my regular cameras and going through the rigamarole of filming, transfer, post-processing, then posting. Making the short clip on the iPhone was incredibly easy and fast. Going through one of my cameras (either the E-M1.2 or the Lumix G9) wouldn’t have looked any better, and probably worse. The problem is that the LEDs in the video clip don’t show the bright saturated colors I see with my own eyes. And that’s with any of the cameras. I stuck with the iPhone output because it actually looked the best of the three cameras with less effort. But there’s still tremendous room for improvement.

tinkering with the black adafruit feather rp2040

whbeebe1 Comment

Everyone by now should know reflexively what the Raspberry Pi RP2040 is ( see https://www.raspberrypi.com/products/raspberry-pi-pico/ if you don’t). It comes in a number of variants from the bare chip to the Pico from Raspberry Pi (with and without headers) to board offerings from Adafruit, Sparkfun, and other board makers. So far I’ve purchased several Picos and several Black Adafruit Feather RP2040s. I’ve powered up both and worked with both, programming them in MicroPython (Pico), C++ (Pico), and CircuitPython (Adafruit). In this post I’m writing about the Adafruit version ( https://www.adafruit.com/product/4884 ). I’ve also purchased and installed one Featherwing OLED — 128×32 Add-on ( https://www.adafruit.com/product/2900 ). I’m interested in that add-on because of its display as well as the three buttons also mounted on the Featherwing. This post is about just the display.

The majority of this code was copied from an example on the Adafruit website ( https://learn.adafruit.com/adafruit-oled-featherwing/python-usage ), starting with the instructions on how to set up the RP2040’s CircuitPython runtime environment.  I copied the example code a few lines at a time to see what happened as each block was pasted in. It was interesting how everything behaved as each block was pasted in and the entire body restarted.

My version of the code has a problem, and it all started with an innocent desire to change the text inside the Label text_area (see line 45). Every other user interface framework that defines label classes provides a simple class method to change the label’s text. I looked but couldn’t find a good public method. Instead I used what is, but Python convention, a somewhat private internal method _update_text() (lines 63 and 65). This coding convention is spelled out in PEP 8:

A name prefixed with an underscore (e.g. _spam) should be treated as a non-public part of the API (whether it is a function, a method or a data member). It should be considered an implementation detail and subject to change without notice.

My use is thus a poor example. But I’ve yet to find the “proper” example. If and when I ever do, then I’ll update the code. But for the mean time I’ll live with it.

I need that capability for my next stage, which is to show via the OLED display when I press button ‘A’, ‘B’, or ‘C’.

import boardimport displayioimport terminaliofrom adafruit_display_text import labelimport adafruit_displayio_ssd1306import time# Initialize the I2C bus connected to the display.# Initialize the display.#displayio.release_displays()i2c = board.I2C()display_bus = displayio.I2CDisplay(i2c, device_address=0x3C)display = adafruit_displayio_ssd1306.SSD1306(display_bus, width=128, height=32)# Fill the background with white. # This is a monochrome display, so there can be only black # or white.#splash = displayio.Group()display.show(splash)color_bitmap = displayio.Bitmap(128, 32, 1)color_palette = displayio.Palette(1)color_palette[0] = 0xFFFFFF  # Whitebackground_sprite = displayio.TileGrid(color_bitmap, pixel_shader=color_palette, x=0, y=0)splash.append(background_sprite)# Draw a black inner rectangle.#inner_bitmap = displayio.Bitmap(122, 28, 1)inner_palette = displayio.Palette(1)inner_palette[0] = 0x000000  # Blackinner_sprite = displayio.TileGrid(inner_bitmap, pixel_shader=inner_palette, x=3, y=2)splash.append(inner_sprite)# Create a text label in the center of the inner rectangle.# This is a monochrome display, so there can be only black# or white.#text1 = "Hello World!"text2 = "Hello Python!"text_area = label.Label(terminalio.FONT, text=text1, color=0xFFFFFF, x=28, y=15)splash.append(text_area)# I wanted to show more than one string on the display.# Looking into the source for label.Label showed _set_text()# and _update_text().# I chose the latter because it only required one argument,# the new text to display.## What is bothersome to me is that _set_text requires two arguments,# the text string followed by a scale value, an integer. When I found# the source on GitHub, the scale argument wasn't being used. To add# insult to injury, that unused argument is required for the function# call.#while True:time.sleep(2)text_area._update_text(text2)time.sleep(2)text_area._update_text(text1)

I’ve also set up my copy of Visual Studio Code as a Circuit Python development environment. I tried to install the one lone plugin that’s supposed to provide this, but it doesn’t work. In the mean time when I want to code I open the file on the devices flash drive and then open a terminal at the bottom and start screen /dev/ttyACM0 115200 which gives me the serial REPL as well as output from any print messages. Please note that /dev/ttyACM0 is the device on my computer, which is running Pop!_OS 21.10. Also note that I’ve also got VSCode set up for Pico MicroPython development which will only support Pico MicroPython development. Another post, perhaps.