Marc's Public Blog - Arduino Hacking

1) Oh, I need to finish writing code to get the SAO badge holder to do something fun

2) Mmmh, why does this python global variable thing doessn't work in the function

3) Goes to re-learn python, with help from gemini and how python forks global variables by default in functions so what you write to them isn't saved at local scope (oh my, why did they do that?)

4) after more hacking, get a proper demo working:

5) publish code https://github.com/marcmerlin/2024-Supercon-8-Add-On-Badge/blob/main/README.md (actual code is here: https://github.com/marcmerlin/2024-Supercon-8-Add-On-Badge/blob/main/software/software/main.py )

6) Oh, I need to make a video demo of the SAO, but...

7) oh yeah, there was that hat on my desk I needed to add LEDs on for an upcoming party, start hacking on that

8) mmmh, the hat won't work long enough with a USB battery, start hacking on a lipo solution

9) ah, lipos work, but the front LED panels rated for 5V start failing around 3.5V, so I need to make a dual lipo solution, one for the neopixels and one for the RGB panels

10) test and measure the dual lipo solution and figure out it will last close to 12H, that's good. Ok, hat works mostly, post that https://www.instagram.com/p/DCYEl1jJd_-
11) Ah yes, the SAO video I was supposed to work on: https://www.youtube.com/watch?v=z7MSywf7js4

12) During that time, I get interesting distracting packages on my doorstep, like lovely flexible LED panels that will hopefully power my future outfit: https://rpi-rgb-led-matrix.discourse.group/t/rpi0-2w-speed-compared-to-rpi3a/913/2

13) While I'm testing them, also try some new rPi0 2w chips and microcontrollers to see if they can power my LED outfit with a smaller form factor (and yes they can): https://rpi-rgb-led-matrix.discourse.group/t/rpi0-2w-speed-compared-to-rpi3a/913 . In the interest of briefty, I'm going to skip the part that included migrating from raspbian to a new dietpi linux distro and port back all my custom changes on it :)

14) That said, I had a long-ish discussion and planning with the electrodragon folks in China on how to make a new 3 channel daughter board that is much smaller and would decrease the over footprint of all new picture frames like the one I built, and of course my LED outfit.

15) but wait, now I also find out there is a new beaglebone solution that does 6 channels output instead of 3? Ok, make a post about it: https://rpi-rgb-led-matrix.discourse.group/t/interesting-6-port-board-beaglebone-pocketcroller-v2/918/2

16) and file a couple of RFE bugs to look into it: https://github.com/hzeller/rpi-rgb-led-matrix/issues/1733 + https://github.com/FalconChristmas/fpp/issues/2054

17) Oh, I just found this old video on my laptop, why did I never post it? Ok, fix that: https://marc.merlins.org/perso/linux/post_2021-01-23_Linux_conf_au-2021-LED-Talk.html

18) Mmmh, so when I quickly posted those pictures from Neil deGrasse Tyson who just gave a talk, I got a reminder it was annoying for my blog system not to be able to link to videos directly without having to upload them to youtube.

19) Ok, learn about html5 video tag, hack my blog system to support videos, and push a new blog with my first video tag: https://marc.merlins.org/perso/outings/post_2024-11-14_Neil-deGrasse-Tyson-back-at-San-Jose-Center-for-Performing-Arts_-An-Astrophysicist-Goes-To-The-Movies_-the-Sequel.html

20) ok, but why did I have to rescue my video from my phone because the H265 recompressed version did not work in the blog? Ah, because of royalties on H265 being too high, most browsers refuse to add support for it: http://marc.merlins.org/perso/linux/post_2024-11-17_Vidrename-Script_-Clean-up-Normalize-Video-Filenames-and-Add-Codec-And-Container-Format-With-Mplayer.html

21) Ok, sure, but now I need to upgrade my vidcomp script to support VP9 and AV1: http://marc.merlins.org/perso/linux/post_2024-11-17_Vidcomp-Script_-recompress-videos-on-linux-with-mencoder-or-ffmpeg-to-div3_-div4_-div5_-xvid_-mpeg4_-h264_-h265_-VP9_-and-AV1.html

22) then I find an Email from a chinese engineer who is willing to talk to me about making better LED shoes. That's exciting, let me reply to him first

23) ok, now I can recompress my videos to VP9, which I benchmarked to somehow be faster to compress and still smaller file size than AV1 (not supposed to be the case, but that's what I'm getting). On the plus side, VP9 works with more browsers than AV1.

24) what as I doing again? (now days have passed). Oh yes, I was supposed to write a blog on hackaday supercon: http://marc.merlins.org/perso/electronics/post_2024-11-01_Pasadena-Hackaday-Supercon-2024.html

25) of course the ridiculous amount of time spent to allow these 2 videos in that post, is a bit hard to justify, but it's really solving a problem I've had for over 10 years, and never got to the top of the pile, because, well, you see what happens when I try to put something on top of the pile :)

26) and I was good, I didn't even play with the micropython rpi micro I received in the mail this week, or the electromage pixelblaze and I/O board, or more LED panels that somehow showed up at my doorstep :)

27) mmmh, and there are all those webcams I ordered and need to configure, but now it's clear I'm going to have to re-install my camera controller, shinobi, from scratch, and that's yet another rabithole...

28) in the meantime I have to finish my LED hat, and design my new shirt and pants for Dreamstate in 4 days... Wish me luck :)

It was very cool that I got to wear my LCA SAO badges for the first time:

This post, because of its 2 video inserts, a new addition to my blogging software, was also an interesting exercise in non linear time and tasks, more on this page: Getting Things Done in an ADHD World

Day 1, Friday

Thanks to Anthony for letting me know about it, and I was able to attend. Went there early on friday for the pre-conf to work on the badges:

the conference badge was this 6 port micropython rPi micro with a couple of SAOs.

they nicely provided food all 3 days

essential geek survival food :)

They gave us a quick primer on how the badge worked, although it would have been better on a webpage with links and info for total beginners who had never used micropython and thorny or knew what thorny was (that included me):

I'm glad I took pictures of these slides, they only made sense many hours later. They should have been online

finding fellow LED geeks :)

learning blinkies for beginners, scan this

While I was there, I 9ound out they had a wonderful 4 bit computer some years back. I actually really regret not having been there that year, programming that in hand crafted assembly would have been epic:

someone hacked a basic I2C on it

people now hard at work

I used the opportunity to bring previous LCA toys and show them off (and fix a few)

People came with plenty of SAOs:

some came more ready than me :)

SAO extenders, cool!

SOA badge holder bag, sweet!

I found Tom Verbeure, the person who had been hacking on RGB Panels with open source FPGAs (colorlight). Cool project for sure. See: https://github.com/q3k/chubby75?tab=readme-ov-file#colorlight-5a-75b and https://github.com/lucysrausch/colorlight-led-cube/tree/master

Also, finally got to meet Henner Zeller, the rpi-rgb-panels author I've been working online with for years:

epic watch!

Also got to meet Daryll Strauss from precision insight, later acquired by VA Linux some 25+ years ago:

People still hacking at night:

I was lit up enough not to get lost :)

Day 2-3, Saturday & Sunday

went to attend a few talks

hacking radio sound and B&W video from a chip, super cool!

learned about an online microcontroller emulator, wokwi, very nice

I got to see a pick and place machine, nice to see them work:

this is what the machine was 'printing'

I tried the SMD challenge, that was hard as hell:

we got old and fat irons, making things harder :)

I couldn't get the last 2 LEDs working, they were so stupidly small

I had someone help me fix mine :)

and they all worked, thank you to the master solderer!

added the result on my badge :)

Random fun shots :)

people hard at work

During the weekend, the SAO wall got populated:

Original from Burning Man

more and more

and more :)

Saturday evening party had a nice real time AI image generator:

some were far out :)

The conf ended with a presentation of best SAOs:

This guy won the contest of biggest SAO, he had a printer working off USB, run by his SAO

Sunday ended with a party at a bar, thankfully I had my battery soldering iron :)

This was loads of fun, and I definitely learned some good stuff. Sad I didn't go earlier but glad I went this year. Thanks bunch to all the organizers and attendeers who contributed!

More pictures: https://photos.app.goo.gl/2hYRaaB5dF5mvv4N8

In 2021 I got my first SAO Conference Badge from Linux.conf.au (clickme for more) That LCA board had 4 SAO ports and came with 2 little cute penguins that I hacked a bit:

one of them was then in charge of running a neopixel necklace

I got a few spare SAOs to attach to my heavily hacked LCA badge :)

Anyway, back to Pasadena Hackaday Supercon 2024, they gave us a 6 SAO badge also running a micropython chip:

attendees nicely donated a few extra SAOs to me, which I wrote code for

even got an SAO extender :)

I had to solder it from parts at the after party in the pub

Back to the conf SAO and code I wrote, here is the result:

Micropython Code:

Main repo:

This was loads of fun, thanks to the organizers!

This is what I started with, 128x192 in P2, P4, and P5 panels

Now let's look at the back and my old (left) vs new mounting method (right). On the left is my "up to then" McGuyver's method of attaching things: using some metal rails with holes, I was somewhat able to aligh enough holes to put some screws in, which kind of held everything together, but not securely:

On the right, a new way to put things together thanks to Marc Estes who laser cut connecting pieces so that each panel could be more securely and correctly attached to the one next to it. Also, note each panel being upside down from the previous one to allow for short ribbon cables and less signal loss, clock drift and crosstalk

Here is the end result of the new panels I put together, the code to reverse panel directions worked:

but the colors were broken, see below

So here is my old 3x4 P5 array next to the new 3x5 array I was building, just testing signal would work:

then rewired everything nicely to be the same orientation

took a while to add power and all the connector bits that Mark Estes made for me

I found those nice power concentrators from amazon

Here are 2 videos that explain the build:

But the colors were wrong. Why? Well, turns out some of the panels were badly wired from the factory and had reversed colors:

So it was all nice and good, until I turned it on:

oh great, some of the panels have broken color order

yeah, that's because I got those panels for free as returns, and they are different generations, some with broken colors. I used the orange and blue labels to tell them apart.

Ok, so since I had a couple of damaged panels and I wanted a nice row of matching panels so that the color intensities would simliar enough, I bought 3 more panels. They came with the orange label, so I wired the orange together, and got this:

Son of a.... The 3 new orange label panels lower left, have fixed colors, so they are not the same as the older orange label panels....

they looked similar enough but they were not

after getting what was going on, I re=wired everything a 3rd time to get bad color panels together

I briefly considered fixing this by swapping the color channels in the ribbon cables but then I figured out it would be less work to fix it in software. rpi-rgb-panel allows for swapping colors on a per panel basis, but not on a per panel basis. Thankfully the code was written well enough to allow very easy remapping of colors per pixel and of course per panel. I also fixed a prior patch of mine that had an unfortunate behavior with Zmapper:v that swapped the order around every time you added a row of panels. Here are the 2 patches:

And after these fixes, finally the panels are oriented the correct way and the colors are fixed:

After more days than planned, it was finally time to mount it on my wall, and that was not trivial, partially because I didn't put enough time into getting proper mounting hardware. I did have some leftover rails I used for added structural integrity, but found out under the wait and stress, they would bend too:

the mounting location was also challenging, made measurements and marks

I used electrical wire as the best hanging wire I had around and put 4 layers just to be sure. Also I found out I had to attach it to the frame in the middle to stop the frame from bending under weight

getting all the attach points under the wire, was totally not trival, but done!

The last thing I had was the native display orientation was portrait, so I wanted to switch to landscape. Turns out rPi3 is too slow to handle an array that big, the data exceeded some internal CPU cache and became very slow, and even more so if I tried the driver's 90 dgree rotate function. So, I tried an rPi4 instead, which showed other interesting electronic bits: the panels on the left are newer and can handle faster update speed while the ones on the right are slower refreshes. This is why it looked like this below. I had to add some delay fasctor in the rPi4 output and then everything was well. Fix was the expected --led-slowdown-gpio=4

See also this page that discusses the cache overflow issues on rPi3, switching to rPi4, and how led-slowdown-gpio can be a bit counter intuitive:

And here is the end result:

What it looks like from the back:

Just like last year, Illuminaughty was about as far across the playa as a camp can be, so it was nice when we arrived :)

Ran into a bunch of people will cool gear:

Very cool hat:

Impressed that the newer panels can bend pretty well

a lot of work went into these patterns

Anthony had a lot of cool gear he built, I was very impressed:

Obligatory group picture:

Thank you to Chuck for organizing this year again, it was lots of fun.

And if you want even more details and history >>> See this full article on the why and evolution of my LED outfit <<<

For all these years, my outfit has relied on a fanny pack filled with batteries, and with an unslightly tether from the fanny pack to the panels, bringing 2 feeds with 5V (as backup and to spread out the amps over 2 wires). That system worked for many years and would survive the failure of one of the 2 5V connections, or even the 16V connection meant to feed the rPi from its own power source stepped down to 5V on the panels (so that it doesn't see a voltage dip on the remote 5V rail when the display sare fairly bright). All in all, it worked, but the fanny pack tether and wires were cumbersome, and some security folks didn't like all the wires.

After switching to a new neopixel controller that is directly USB powered, it made more sense to power the panels locally and put the batteries on the panels:

For comparison, the old panel on the left only has the rPi and a small 16B to 5V converter and than relies on that tether cable to the white box on the left which has the DC-DC step down and the ESP32:

finished design with padding, power routing from 3 lipos or 2 USB attery packs

While this was not new for v6, made sure the camera still worked, it turns out to not be super reliable on batteries, but when it works, it's a crowd favorite:

The new version works like the old one, but with batteries directly attached to the panels, which in turn makes them much heavier, but oh well. Video with Lipos and DC-DC converter:

However, the more interesting upside is that I could also replace the 16V lips that get stepped down to 5V, with 5V USB Battery packs. the reason I never did that at the time is that the entire system takes way more than the maybe 2.5A you can get from USB packs on a good day. A somewhat cumbersome workaround to this problem is to use 2 USB battery packs with 2 independent outputs each, meaning 4 independent 5V busses able to put out up to 2.5A depending on the battery pack. So, I split my power system in 4:

In total it means the whole thing uses about 3A at 5V, or 15W, which means 180Wh for 12h. In theory 2x 99Wh battery packs would work for 10H, but in real life, the first battery pack gets a lot more load since it runs the rPi, so it only really lasts about 7H before I have to replace it. Not ideal, but still nice that I can run from USB instead of lipos if needed:

Video of the USB version:

After some unfortunate feedback soon after I built the new version, I added a makeshift back cover with duct tape, mostly to hide the "scary" electronics, while still giving me accesss to them since this is still a prototype that needed occasional work and tweaks:

Since the original design with lipos, the good news is that lipo chargers have finally become much smaller. They are now small enough that I can simply leave one in my travel backpack forever:

Now I don't need this "custom made" battery box ;) which worked for its time, but didn't allow bigger batteries being an issue during 12H festivals (2 batteries wasn't enough), and was an issue during airport inspections when they wanted to "see inside the box":

I however found out over time that some airports really didn't like to see the panels in X-Ray with batteries attached. All airports were fine with the panels on their own, and the batteries on their own, but if I left the batteries in the outfit, which honestly is a lot more convenient to me, some airports really freaked out in totally irrational ways and now complained about "too many wires" "looks like a bomb" and all that good stuff. The 2 airports that delayed me enough that I barely made my flight (bangkok and Ontario, CA), literally said they would have been fine if I had packed the batteries together and still carried everything I was carrying, just not plugged in (of course everything was off, and plugged in is actually safer since you don't have loose power connectors that could somehow short).
So I'm not interested in missing a plane due to this and honestly nonsensical and irrational reactions (after all, no one said fear was rational or logical), so I eventually made a "battery pack" that I can more easily slide in and out before and after each flight:

Oh yes, it's still home made looking, could somehow get/make a box for it, but if I do they'll want to open it to see inside, going back to the original box I had earlier, so I'm not sure there is a good way to win this. Also if I make it look too much like one battery instead of 3, they'll complain it's 290Wh (over the limit) instead of 3x 98Wh (under the limit).

And to show how things evolved, this was the v3 outfit with neopixels and only 24x32 instead of 128x192, but much brighter. I did use v3 a couple of times again at day festivals, as it can be made bright enough to work in full daylight, but after doing this a few times (and that required extra batteries), I decided not to bother anymore, and skip the LED panel during day hours (I still have LEDs on arms and legs that can be made bright enough if need be):

Separately, I often have to explain to people, that my outfit is actually a scaled down version of the RGBPanels you see on stage. Once you have the display, it can scale up:

And another question I get is "how long does it last?". 2 batteries of my old 5Ah 4S lipos, was a bit short for an all night 12H festival (EDC), but back then I was also powering the LEDs on my arms and legs, which took an additional non trivial amount of power. For wiring ease, the LEDs are now on a separate battery, which allows the main system to run longer. I also upgraded the batteries from 5Ah to 6.7Ah. As a result, I found out a bit after the fact that actually 2 batteries would have been enough, since I put 3 as per my old setup, I ended up with a full runtime of just under 19H (I stopped the test before the batteries were totally drained since it's not great for them to do so). As I'm writing this, I now realize that with just 2 batteries, I could last 12.5H, which is still more than enough (and it would remove some weight, so I may want to consider that.

310Wh out of my 3 batteries, more than I thought, and almost 19H

because all meters have measurement errors, recharging pushed back in 20.4Ah instead of 21.2Ah which doesn't quite add up, but close enough

Version 5 was a bit upgrade with my P2 run rPi run RGB Panels for a resolution of 128x192 per side. The oldest part of the outfit at this point were actually the Neopixel strips I've had for about 5 years, and despite being more reliable WS2813B with backup data line, the PCB traces would break and the chips solder points would eventually break too. The amount of time I've spent fixing and replacing LED strips is more than I'm willing to talk about, but there was just no good alternative, until now.
In the past, flexible LED strands with wires between each pixel did not have enough density, maybe one pixel every 5cm, which was not acceptable for my use. And after many years of waiting, a company finally made P15 flexible strands, one LED every 1.5cm, which looks much better and is even a bit more dense than my previous strips that were P16.6.
Here there are: https://www.aliexpress.us/item/3256804447608449.html . Update, don't buy these, they are shit and broke within hours. See at the bottom

While I was at it, I added a small programmable 16x32 panel to my fanny pack, because why not (the existing fanny packs didn't have sufficient storage, so I ended up decking out mine), and here is the end result:

I have no idea how reliable the strips will be, and unfortunatley they are WS2811 without the backup data path that WS2813 had, but time will tell. I'm bringing it to EDC and we'll see what happens :)
Update: these broke within hours, they were crap.

Version 6.5.1: Ray Wu Strips

It ended up being more solid, but the flexing and occasional pulling on the bare strips that were attached with safety pins (I didn't want to glue or sew because it would then be unwashable), eventually caused the strips to fail, although it was more slowly. It worked for 4 festivals in Europe and required some resoldering, but it was not terrible. Still, it wasn't a long term solution either.

Version 6.5.2: Full LED Tubing Protection

This is now going to burning man, I hope it will hold, especially with lots of biking :)

once I got the servo validated, I connected it to an ESP8266 as a wifi controller

Here is the basic end result:

The one downside of the ESP8266 is at least the one I have with the firmware I'm using, does not have super reliable Wifi connectivity, so my server keeps track of it being there or not, and can remotely power cycle it as needed. Not ideal, but it works...

There are predators (hawks at least), so I had to add a full net around the area:

cute chickens

This is the door in action after I added a switch to control it locally and wrote code on my home controller to talk it is via wifi:

The last thing I wanted to add was a water level monitor, especially because I had issues with the dispenser leaking, and ending up without water, is bad obviously. My first plan was a predictable total failure;

looks wonderful, but it's not meant to stay in the water and the board, failed

2nd try with pins

oh look, lots of metal ended up in the water, of course!

So yeah, all those classes in middle school about electrolysis are not just to bore you, it is a real thing, and sending current to sense the water through conductors causes ions to move and metal too:

So, I tried again with new conductors and changed my code not to check for water constantly but only 20 seconds every hour. That's thankfully enough that it mostly stopped the issue I had:

And obligatory cute chickens and chicks videos:

And by the time I was almost done, I got 4 more, so that was enough for 192x128 with 12 panels. That happened to be the exact resolution of my LED outfit, although that one was 128x192. For wiring reasons and optimizing refresh speed with 3 parallel channels, I wired the array the wrong way display wise, but the best way hardware-wise:

Thankfully rpi-rgb-panel has a mode to flip, mirror and rotate the output, so it was easy to get back a 128x192 display, and run th exact same code that my outfit. This nicely allowed me to see the same thing between P2 and P5 pixels:

I now have 3 frames, fun :)