Arduino Coding Fun iOS Projects

Flip Dots! The technical bits.

I first want to acknowledge that I did the thing that I try to never do: I showed off a snazzy project, left some hints here and there of how it worked, said I would follow up with full details… and never did. That’s lame.

I’ve had multiple people reach out for more info and I’m glad they did, since that’s pushed me to finally get some repos public and this belated follow-up written. Apologies!

To jump straight to it, I’ve published these two repos:


Let’s first go over the hardware involved. The most important piece, of course, is the Alfa-Zeta XY5.

In my case, the 14×28 board was made up of two 7×28 panels connected together via RJ-11.

The panels are pricey, but they can be thought of as “hardware easy-mode”. Alfa-Zeta has done the hard job building the controller that drives the hardware and all we have to do is supply power and an RS-485 signal that abides by their protocol.

If you purchase a panel from them there are two important documents to request:

  1. The main manual that describes the specs, features, and things like the DIP switch settings.
  2. The protocol for sending commands to the controllers (which is really simple).

These can easily found by searching around, but if you own a panel the company should supply them. Most of the protocol can be deduced by looking at open source code.


The 24V -> 5V converter isn’t necessary if you supply power to the MCU independently, say through a USB power adapter.

Connection overview

  • 24V DC goes to both panels
  • 24V DC goes to the step-down converter, 5V DC goes to the 5V input of the NodeMCU
  • NodeMCU is wired to the RS-485 to TTL converter
    • VCC -> 3.3v
    • Gnd -> Gnd
    • DE -> 3.3v pulled high because we're always transmitting
    • RE -> 3.3v pulled high because we're always transmitting
    • DI -> TX[x] x being 0 or higher depending on board
    • RO -> RX[x] most boards only have the main serial IO, but boards like the Mega have multiple
  • RS-485 -> Only one panel controller – not both

An Arduino Mega is driving the board in this photo.



See for the code that runs on the MCU.

At the moment there isn’t much to it – you can either compile the firmware to run in a mode that writes data from UDP packets to the board, or you can draw “locally” using Adafruit GFX methods.

See the README in the repo above for more details.

iOS / iPadOS / macOS

See for the code that runs on these devices.

Semi-interestingly I utilized Adafruit GFX again, this time via swift-gfx-wrapper to draw to the board over UDP. It’s hacky and experimental, but that’s part of the fun.

See the README in the repo above for more details.

Fun iOS Projects

SpriteKit SnowFlakes

From the seasonal hacks department, here’s my toy app to make it snow on macOS. ❄️

How it works:

When the app is told to make it snow it adds full-screen non-interactive windows on each display and inside those windows adds a SpriteKit view with a scene inside that contains emitters.

That’s basically it!

Arduino Fun iOS SwiftUI

NeoPixel tree progress

This weekend the NeoPixel tree got many much-needed updates!

Though I have more ideas to implement, the basics of what I wanted to do are complete, like sending commands remotely.

What we can currently do:

  • Set the brightness
  • Change the color
  • Turn the pixels off
  • Run some built-in sequences, like a nice rainbow
  • Set repeating color patterns
  • Set individual pixels

I also threw together a really quick iOS app to set the color with SwiftUI’s built-in ColorPicker view. Thanks to the Rover project (another one that’s been neglected), I had some UDP client code I could borrow to speed up development.

Changing the color of the tree with a SwiftUI ColorPicker view.
Apple Fun iOS Retro Computing

iPadOS on a CRT

I have lots to post about related to my recent vintage / retro computing adventures, but in the meantime here’s iPadOS on a CRT.

It’s actually kind of nice! The biggest downside, however, is that the CRT only ran at 1280×1024@60Hz. The resolution is fine, but the refresh rate is quite low for a CRT – my eyes wouldn’t be able to handle it very long. I’ve always been sensitive to rates lower than 85Hz on CRTs.

The hardware to make it work:

  1. A CRT.
  2. An iPad.
  3. An Apple Digital AV adapter which has HDMI output, such as this USB-C one.
  4. An active HDMI -> VGA adapter such as this one (it has to have external power).
  5. A USB hub is nice for wired peripherals, but optional. I have a wired Microsoft Optical mouse with a Keychron C1 (reds) connected in this video.
iOS Nerd Sniped Swift

UITextView, autocorrect, and custom attributes

For this week’s “Nerd Snipe”, I spent way too much time at work trying to track down a pesky bug related to our editor. Long story short, we send some custom NSAttributedString.Keys to signify differences in rich text. For instance, a heading attribute with an integer value may tell a parser to wrap text in an <h2> when converting the string to HTML.

Oddly, sometimes that special attribute wouldn’t be included when text was autocorrected, so the generated HTML wasn’t always what we expected. After a lot of digging I believe this could be a bug in UITextView (or maybe NSTextStorage).

Inspecting the value of attrString in the NSTextStorage function func replaceCharacters(in range: NSRange, with attrString: NSAttributedString) after autocorrecting some text shows that it only seems to include attributes that were defined in Foundation (e.g. NSFont, etc.), but not our custom ones.

Regular typing works fine – you see all the expected attributes set in textView.typingAttributes.

In scenarios like these I like to make the simplest example to help confirm I understand it, so I’ve made a repo demonstrating the issue in case it’s helpful for anyone.

iOS Projects Thoughts

Happy New Year!

iOS Projects Swift SwiftUI

Wyze Cam in iOS

Arduino Coding iOS Projects Swift SwiftUI

Flip Dots!

I saw flip dots (also called flip discs) last year for the first time and instantly knew I needed some in my life. If you’re not familiar with them, check out how they work!

The particular model I have is the ALFAZETA XY5, which may be the easiest way to get up and running, but certainly not the least expensive.

After getting the board, all you need is:

  1. 24V power supply
  2. Something that talks over RS485 (in my case I used an ESP8266 connected to a MAX3485 board)
  3. Their documentation that defines the controller data protocol

I plan to write in more detail how it all works, but for this demo the stack is:

  1. SwiftUI app that runs SwiftGFXWrapper (which is mainly Adafruit’s GFX Library under the hood)
  2. The app sends the entire pixel buffer over UDP to the ESP8266
  3. The ESP8266 sends data to the XY5 over RS485 using their controller’s protocol

Update: Here’s more info on how it all works!

Arduino Gadgets iOS Projects

iPad Zoom mute button

At work we’re primarily using Zoom for meetings while we’re in remote mode. Due to the recent problems found in their desktop software, I run it only on my iPad to provide a little more security (thanks to iPadOS’ sandboxed environment), plus the front facing camera on my iPad Pro is superior to my iMac and MacBook Pro’s.

The first issue I found with this setup was that I wanted to get the iPad into a position more perpendicular like a web cam, rather than the angled up shot below my face. I don’t think anyone wants to look up my nose unless I’m on a telehealth call, so I ordered this flexible stand for about $25 from Amazon and got it mounted:

Trying to bend this thing will give you a workout.

So far so good, until my first meeting. I wanted to follow conference call etiquette by muting myself when I wasn’t speaking, but it was a pain to reach and manually tap the mute button every time. Plus, although the flexible arm is super strong, it’s still going to wobble wildly if you touch the iPad and your video is going to show that.

Was there a way I could toggle muting myself without touching the iPad? After a quick Google search, the answer was YES!

The attached keyboard (Smart Keyboard Folio, Magic Keyboard) didn’t make any sense in this case, but a Bluetooth keyboard would be perfect!

Logical answer

The logical answer is to connect up a Bluetooth keyboard and hit Command + Shift + A when you want to toggle muting your mic, and you’re done. That’s it.

I’m not totally logical

Of course, the route I chose was different. I have enough keyboards on my desk, I really just want one button to do one thing.

Recently, I rigged a button to turn pages in the Books app over Bluetooth. We should be able to do the same thing here, right?

Figuring out the codes

The objective is clear: When we press a button, we send “command+shift+a” to the iPad.

Using Adafruit’s HID codes, we find:

  • Left shift == 0x02
  • a == 0x04

But what’s the “Command” button? Is that the “meta” or “GUI” key? If so, is it a modifier or just a regular key?

Lots o’ troubleshooting

I spent a lot of time troubleshooting over and over:

Compile a new sequence of commands, upload new firmware to the microcontroller, re-pair with the iPad, open Zoom and try to mute: No go.

From what I could tell, “shift + a” were working, but “shift + command + a” wasn’t. It wasn’t until I almost gave up that I had a breakthrough:

Let’s try remapping another key to “command” and see if we can press that key. How about Caps Lock?

It worked.

In my code I wrote:

// gold
ble.println("AT+BleKeyboardCode=02-00-39-00-00-00-00"); // shift + caps lock
ble.println("AT+BleKeyboardCode=02-00-04-00-00-00-00"); // shift + a

This is as if the user pressed “shift + caps lock”, and then “shift + a” at the same time, then released. Now the Zoom app was getting the proper command from a Bluetooth “keyboard”.


This setup is virtually identical to what I have here, it’s just a different button.

The USB cable coming in is only for power, and if I had the Adafruit Feather version on hand I would’ve used that with a battery so the box would be totally wireless.

The button is no more complicated than this tutorial.



A better version of this would be:

  • A button to also toggle video
  • Using the Adafruit Feather BLE version with a battery so the box would be entirely wireless