LightWalker 2.0

My first shot at LightWalker was way more involved and elaborate than I originally planned and definitely more involved on the hardware side than I thought I could deal with. But, it did actually work. Mostly.

I don't know how most people face difficult problems they've never handled before, but whether it's rebuilding an engine, repairing a hole I put in the wall, or something like LightWalker, I usually do it once just to figure out what the hell is going on and then immediately do it again to do it correctly. Now, I'm definitely still a noob when it comes to hardware and embedded stuff, so I'm not going to claim that I'm doing everything correctly here, but I do think it's a step in the right direction.

Main complaints from LightWalker 1.0

• Difficulty producing desired results in the RGB color space
• Lack of memory available
• Limited frame rates possible with the Arduino Mega (ATmega2560)
• Overall bulkiness of the unit
• My own half-baked software design

So, here's LightWalker 2.0 so far:

Initial  build of LightWalker 2.0

• Hardware
• Teensy 3.1 (32-bit ARM Cortex m4, 72Mhz, 256Kb Flash, 64Kb RAM)
• Schmartboard SMT to DIP board sporting a TI PCA9546A I2C multiplixer allowing communication to four ADXL345 ±16 g accelerometers
• Bluefruit EZ-Link bluetooth
• Electret microphone
• Software
• Moved away from Cool Neon and Chris De Vrie's TCL Arduino library for controlling lights and to FastLED 2.1
• I also removed my MSEQ7 shield and am doing audio processing in software now. This allows me to do a bit of max/min adjustment on the fly instead of having to cover the microphone in hot glue to deal with being within a half mile of an 85k watt stereo.

This is currently all on a blank perf board and wire wrapped together. Not sure if I'm going to just throw some solder on top of it and call it good or re-do on a better breadboard PCB or what. And, this is also still controlled/configured by a revamped android application running on Android KitKat.

As you can see, this is way more compact than an Arduino mega with two shields and a separate bluetooth breakout board. Hell, the whole thing is smaller than the mega alone! But, the main advantage to this new unit is speed and lighting effects.

Before I get into the speed portion, I've gotta say that using FastLED to work in the HSV color space is amazing. I've only touched the surface of what you can do, but it is extremely simple to create smooth and subtle LED effects when working with HSV. You can easily create transitions between colors instead of just doing a hard switch from one to the other. And making things smooth and subtle is the name of the game when it comes to LEDs. Otherwise they hurt your eyeballs. 

Now for the speed thing. This is kinda interesting to me...

configuration/mode	equalizer (fps)	gravity* (fps)	sparkle* (fps)	pulse (fps)	bubble* (fps)	rainbow* (fps)	zebra* (fps)
LightWalker 1.0, arduino, TCL	87	7	18	93	16	n/a	n/a
LW 2.0, arduino, fastLED 2	36	7	15	135	16	25	32
LW 2.0, arduino, fastLED 2.1	35	7	15	135	16	25	33
LW 2.0, teensy 3.1, FastLED 2	98	86	81	173	90	85	73
LW 2.0, teensy 3.1, FastLED 2.1	250	124	130	465	134	123	100

[Update] Note that all of these tests are done against a strand of 352 P9813 driven RGB LEDs (AKA Total Control Lighting)

Couple things to keep in mind:

• The equalizer mode on the arduino is using hardware to calculate "loudness". The teensy configurations are using software to calculate the same. Obviously something is off with the equalizer stuff in 2.0 as the frame rate was chopped in half when it should have stayed the same or gone up. It's on my to-do list to look into it.
• FastLED 2.0 does *not* officially support the P9813 chip that I'm using in my Cool Neon TCL strands, but I was able to port the 2.1 code for that chipset to the 2.0 release. That's what my FastLED 2 testing was run against. That was not an official FastLED 2 release.
• The different modes obviously do a bunch of different lighting effects and some are more complex and slower than others.
• The modes marked with an asterisk read data from four different accelerometers and perform calculations  on the data *for each frame*. This is why the pulse mode is so much quicker than the others, it is not reading any sensor data for it's effects.

Some conclusions

• The obvious result is that it pays to be on the new hardware and on FastLED 2.1. Now hopefully 2.1 is officially released soon...
• I think it's fairly interesting that the arduino based platform didn't benefit from the move to FastLED 2.1 from a speed perspective. The no-sensor-reading pulse mode did see about a 40% increase on the TCL -> FastLED 2 move, so my guess is that the sensor reading and calculations I'm doing are so slow on the arduino that the LED writing speed is negligible.
• The 100+ average frame-rate is really really nice for doing smooth LED transitions and effects. I'm really happy to see this kind of improvement and am already adding new effects based on the new abilities.

The code is up at https://github.com/gerstle/LightWalker if you want to check it out. Think that's all I've got for now, but now that I have two full LightWalker controllers...

Upcoming events

Got some fun stuff coming up in the next couple weeks that LightWalker will be making a showing at...

First off, it's San Francisco Decompression on Sunday the 13th. I'll be there post brunch to hang out, dance, and enjoy the sights. Come sunset, LightWalker will stroll about and help light up the streets.




Then on Friday the 18th, I'm back in downtown Santa Cruz with the Museum of Art & History's GLOW Festival. It's a two night affair involving mostly fire on Friday and LED electronics and LEDs on Saturday. I'm being a rebel and will be there Friday cause they have more space that night and I want to go surf in Big Sur on Saturday. So, LightWalker will be walking the streets of Santa Cruz and dancing with Samba Stilt Circus and the Dancetronauts within the GLOW Festival from 7PM - 10PM.

Come join me!

birth of the playa creature

LightWalker's true birth happened this past week in Black Rock City, Nevada on the playa of Burning Man 2013. I won't bother you with words...

Wiring almost complete and one arm lit!

LightWalker

Have been able to spend a fair amount of time on the ol' LightWalker project lately. Pretty happy with how it's progressing...

• Main unit is completely wired up at this point. All I gotta do is figure out where to mount the mic and how to insulate it a bit and that piece is done!
• Both legs are completely done... frames, lights, wiring, and fabric covers.
• Both arms have their frames built.
• One of the arms has lights installed.
• All wiring for accelerometers is complete.

First stroll!

A couple weeks ago, I actually wired the legs up, threw the battery and controller in a backpack, and hopped on the leg stilts to see how they worked. Definitely found some things that need polishing, but overall, the first walk went fantastic!

first arm

Here's the arm I got wired up with lights today. Now I just gotta get the lights on the other arm, finish wiring it, and it's on to my actual costume! I think I'm going to need to make an all white stilt outfit with 50 or so pixels in the legs to really make the whole thing work. Might even get a bunch of white fabric to hang off of me so I look more flow-ey.

The man burns in 47 days. At this rate, I might even have time to pack and get some food before I have to head out.

Cheers. Minty.

She has a heart

This is not quite everything I wanted to get accomplished this weekend, but I did make some solid progress. All the electric components are soldered and working! In the process, I realized that I know nothing about soldering. Best lesson? Keep your soldering iron tip clean!

It took me quite a while to get everything drawn out and even longer to get it all soldered and working, but it was a great learning experience and super fun.

This is the entire unit... arduino, i2c multiplexing shield, equalizer shield, bluetooth breakout board, 4 ADXL 345 accelerometers, and an electret microphone. Only things missing from the shot are the 450 LED pixel points, the 6v 12Ah sealed lead-acid battery, and another battery to run this unit (I'm going to run the lights and controller off of separate batteries).

LightWalker's guts.



This is the i2c multiplexing shield with TCA9548A i2C switch. It allows me to hook up the 4 accelerometers that all have the same i2c hardware address to a single i2c line. The board can handle up to 8 units with the same address, so maybe I should do a spider for next year?

The big trick here was that I hooked up my SCL and SDA lines to where they were printed on the board but failed to realize that the board didn't connect those to the arduino's analog 4 and 5 pins like my board needed. I think newer boards would work through the stackable headers and the SCL and SDA holes printed on the board. Once I realized I was working with an older setup and re-routed them, all was good.





bottom of the i2c multiplexing shield

top of the i2c multiplexing shield







Here's the equalizer shield. I'm only using one of the  MSGEQ7 chips on here for a single audio channel, so it's kind of overkill, but it does give me a nice stackable shield and pins to hook the microphone and bluetooth to.



equalizer shield w/
electret microphone

And, just for completeness, the arduino compatible shield from seeedstudio...

the seeedstudio arduino
compatible board I'm using

Motivation Vitamins: Maker Faire

400 total control lighting pixels!

Wow, have you guys ever been to the maker faire?! It is amazing! Highlights include stilting around with the Stilt Factory crew, watching the life size mousetrap, listening to Arduino founder Massimo Banzi talk about what Arduino's working on, and chatting it up with Cool Neon.

Stilt frame sketches

And check out the little self-Santa'd Christmas present I got from Cool Neon this week! Oh yeah. I've completed the design for my stilt frames (check it out below) and will be building them out over the long weekend. And these bad boys are gonna be set into the stilt frames about every inch and a half. Thing's gonna light up like Vegas!

bringing the beats

shot of the horribly messy
prototype hardware

Getting audio working on Lightwalker has been a huge pain. I played around with a few electret microphones (like this guy from sparkfun) and had some bad luck with getting it to do what I wanted. In fact, I couldn't get it to do anything worthwhile. I even went as far as switching to using my android phone as the microphone and sending volume commands to my arduino over bluetooth. Doing so requires you to calculate root mean square and count zero crossings and all sorts of audio processing that I haven't done before. Was really cool to play with and tweak. But, in the end, doing the calculations in software and sending over bluetooth turned out to be way too slow.

I ended up landing on using a spectrum shield from sparkun in conjunction with their electret micrphone breakout board. Thought the whole thing was shot when I got it. And then I realized their documentation is incorrect and you have to run the mic at 3.3v instead of 5v. Has been great since I switched it. I might end up switching to just using an MSGEQ7 instead of the entire shield, but this is fine for now.

Another challenge I ran into was trying to figure out how to make it deal with the quiet of deep playa and being on the edge of a major sound camp. Once again, moving averages to the rescue! By keeping a moving average, I can compare the current volume to the average and adjust what the peak is as I go. So, moving from a quiet environment to a loud one or vice-versa will allow the lights to react visually well in both settings.

Check out the video. The lights and music are a little more synchronized in real life, but you get a good idea.