For my Lilliputian Alien Abduction costume I wrote a class called ReAnimator that generated all the UFO’s LED animations. To make it easier for someone to demo all the animations I wrote a program that runs all of the patterns and shows how to use the ReAnimator class. Here’s a video showing all of the patterns combined with different overlays.
I reworked the code and the article for Project Ouroboros. You can see the update by clicking here. When I originally wrote the article in 2011 a USBasp programmer was around $6 on eBay, but now you can buy one in 2019 for about $1.50; pretty amazing.
Here’s some code I wrote for the USBasp programmer board I played around with in Project Ouroboros. A bit surprisingly I had no trouble powering a WS2812B strip with just 3.3V. If you run this code on a 5V board you should change LED_STRIP_VOLTAGE to 5, although it’s not strictly necessary because that number doesn’t actually control the voltage. If you do change it to 5 then the power allotted to the LEDs will increase and they will get brighter. I tested the board with 100mW for the LEDs and I had no problems.
#include
#define NUM_LEDS 8
#define DATA_PIN 12 // MISO pin
#define FRAMES_PER_SECOND 125
#define LED_STRIP_VOLTAGE 3.3
#define LED_STRIP_MILLIAMPS 20
CRGB leds[NUM_LEDS];
void setup() {
FastLED.setMaxPowerInVoltsAndMilliamps(LED_STRIP_VOLTAGE, LED_STRIP_MILLIAMPS);
FastLED.setCorrection(TypicalSMD5050);
FastLED.addLeds(leds, NUM_LEDS);
pinMode(14, OUTPUT); // green LED, LOW == ON
digitalWrite(14, HIGH); // turn green LED off
}
void blink() {
static uint8_t i = 0;
uint8_t brightness_bool = i++/128;
digitalWrite(14, !brightness_bool); // green on board LED, LOW is ON
leds[0] = CHSV(0, 255, 255*brightness_bool);
}
void breathing() {
const uint8_t min_brightness = 2;
static uint8_t delta = 0; // goes up to 255 then overflows back to 0
// for the LEDs in the current state setting the brightness higher than max_brightness will not actually increase the brightness displayed
uint8_t max_brightness = calculate_max_brightness_for_power_vmA(leds, NUM_LEDS, 255, LED_STRIP_VOLTAGE, LED_STRIP_MILLIAMPS);
uint8_t b = scale8(triwave8(delta), max_brightness-min_brightness)+min_brightness;
FastLED.setBrightness(b);
delta++;
}
void loop() {
static uint8_t dynamic_hue = 0;
//blink();
//fill_solid(leds, NUM_LEDS, CHSV(dynamic_hue, 255, 255));
fill_rainbow(leds, NUM_LEDS, dynamic_hue, 21);
//breathing(); // breathing isn't meant to be run by itself. combine it with one of the functions above.
EVERY_N_MILLISECONDS(100) { dynamic_hue+=6; }
FastLED.delay(1000/FRAMES_PER_SECOND);
}
If using a FastLED function (e.g. FastLED.setMaxPowerInVoltsAndMilliamps()) to manage how much power your LEDs use FastLED limits the maximum brightness that can be set to a value that does not exceed the requested power draw. So if FastLED determines your power limited maximum brightness is M then calling setBrightness() with a value greater than M will result in FastLED setting the brightness to exactly M.
A breathing effect ramps the brightness up until it reaches the maximum brightness then ramps the brightness back down to a minimum brightness then starts the whole cycle over again. A naive approach would be to use a triangle wave that goes from 0 to 255 and back down to 0 as the input for setBrightness(), but if the power limited maximum brightness M is less than 255 then the brightness will plateau at M, and the brightness will remain fixed until the triangle wave input falls below M again. My breathing() function achieves a continually changing brightness by setting the peak of the triangle wave to M. However, M changes based on the number of LEDs currently lit and their colors, so breathing() recalculates M before setting a new brightness value.
Snippet from the breathing code example available on GitHub:
void breathing(uint16_t interval) {
const uint8_t min_brightness = 2;
static uint8_t delta = 0; // goes up to 255 then overflows back to 0
static uint32_t pm = 0; // previous millis
if ( (millis() - pm) > interval ) {
pm = millis();
// for the LEDs in the current state setting the brightness higher than max_brightness will not actually increase the brightness displayed
uint8_t max_brightness = calculate_max_brightness_for_power_vmA(leds, NUM_LEDS, 255, LED_STRIP_VOLTAGE, LED_STRIP_MILLIAMPS);
uint8_t b = scale8(triwave8(delta), max_brightness-min_brightness)+min_brightness;
FastLED.setBrightness(b);
delta++;
}
}
You may have read that you need to apply gamma correction or convert luminance to brightness so that the LEDs have a linear response. That is what I tried first, I never had success with that approach because of the clamping effect FastLED’s power management. After I figured out I had to determine the maximum brightness possible under power management conditions I found that the output of the LEDs looked linear to me using just a triangle wave, so I didn’t try to apply a correction curve. A point that confuses me is whether setBrightness() is actually controlling the brightness or the luminance. I couldn’t find a correction curve being applied when looking through the FastLED code.
The function calculate_max_brightness_for_power_mW returns the same value as calculate_max_brightness_for_power_vmA so I’m mentioning it in this write-up to help people find info on it too.
My example breathing code on GitHub
FastLED’s notes on power management
Power management functions documentation
LED Brightness to your eye, Gamma correction – No!
I created a pulse oximeter sensor using an ATmega32U2, a TSL230R, one red and one IR LED, and a clothes pin. The ATmega32U2 is used to read the frequency data from the TSL230R, control the LEDs, and send a stream of data to the host machine over USB. I wrote the code for the microcontroller in C and utilized the LUFA framework.
I wrote a python program called pulseox_graph.py to receive the data from the microcontroller and display the photoplethysmogram, heart beat, oxygen saturation data.
My AGPtek M20 and RUIZU X02 mp3 players have an odd way of ordering the mp3 files saved on the device. While you can save mp3s sorted into different directories onto the player it will still sort the files alphabetically as if they were all in one directory. From comments I’ve read using fatsort (or a similar program) on the device will make the files appear in the correct order, but it didn’t solve the problem for me; neither for the internal storage nor an sd card. This bash script will prefix all of your files with a unique number so that mp3s that share a directory will be listed/play next to each other by the player.
#!/bin/bash
# Copyright 2019 Jonathan Thomson
# Permission is hereby granted, free of charge, to any person obtaining a copy of
# this software and associated documentation files (the "Software"), to deal in the
# Software without restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
# Software, and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
# AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
# rename4AGPtek.sh
# Adds a sequential prefix to every mp3 file on the AGPtek or Ruizu player so that
# it plays them in the correct order.
#
# If you run this script on the files on your player, then add a new file to your
# player and run the script again it will delete all of the prefixs, and add on new
# prefixes to all the files so that your new file will put in the right place
# alphabetically.
#
# MP3_DIR is the directory of your player. It's better to use this script to rename
# the files after they've been copied to the player.
#
# The ZERO_PADDING variable depends on the number of files and must be set correctly
# for files to play in the right order.
# e.g. if you have 10s of files ZERO_PADDING should be set to 2, 100s of files
# ZERO_PADDING should be 3, 1000s of files it should be 4, etc.
#
# If the number of files on your player increases from, for example 99 to 100, you
# will need to set REMOVE_PREFIX_ONLY to true, run the script, increase ZERO_PADDING
# from 2 to 3 and set REMOVE_PREFIX_ONLY to false, and then run the script again to
# get the correctly zero padded prefixes.
#
shopt -s nullglob
IFS=$'\n'
MP3_DIR="/media/jthomson/9016-4EF8"
ZERO_PADDING=4 # zero padding, e.g. 4 --> 0001)
REMOVE_PREFIX_ONLY=false
i=1
dirlist=$(export LC_ALL=C; find $MP3_DIR -type d -print | sort)
for dir in $dirlist
do
cd $dir
echo $dir
# strip the prefix off and sort so when update the prefixes so the prefixes are sequential with the filenames in alphabetical order
sorted_base_filenames=$(find -mindepth 1 -maxdepth 1 -type f -name "*.mp3" -print | sed -r 's/^\.\///' | sed -r "s/[0-9]{$ZERO_PADDING}\) //" | sort)
for f in $sorted_base_filenames; do
current_filename=$(find -mindepth 1 -maxdepth 1 -type f -name "*$f" | sed -r 's/^\.\///')
base_filename=$(echo $current_filename | sed -r "s/[0-9]{$ZERO_PADDING}\) //") #stripped of the number prefix if it has one
if [ "$REMOVE_PREFIX_ONLY" = false ]; then
new_filename=$(printf "%0${ZERO_PADDING}d) $base_filename" "$i") # add prefix zero padded
else
new_filename=$base_filename
fi
mv -i -- "$current_filename" "$new_filename" &>/dev/null
echo $new_filename
i=$(expr $i + 1)
done
cd - 2>&1 >/dev/null
done
