There’s been a recurring theme of graphical blinking eyes in Adafruit projects. It’s practically a Halloween tradition each year, revisiting and evolving an earlier eyes project into something more realistic or more easily customized. It became the whole focus of two subscription boxes: Adabox 009: HALLOWING and Adabox 013: MONSTER M4SK.

…Also learned that Costco has a similarly-priced offering in the shape of a dragon!

_{Photo credit: Costco.}

First, it’s not even an original idea…intellectual property rules might even call it an “obvious invention,” bound to come up when you have eye-sized displays. AIBO and Furby have used LCD eyes for some years now. Ours evolved from an earlier project with LED matrices, itself a well-trodden sci-fi trope.

As an engineering education company, we make great kits and offer parts. We don’t sell ready-made Halloween decorations, fun as they are, in the same way that, say, Apple doesn’t make toaster ovens: it would only be a distraction from our core focus, it’s not “lost profits.” So we’re cool that someone else does, and happy if our stuff helps. A candle is not diminished by giving another candle light.

^{Photo credit: Home Depot}

This is not a full review of the werewolf prop. You’ll find plenty of customer reviews on these products’ web pages. But overall, as store-bought (not DIY) yard haunt items go, it’s an impressive amount of monster for the price. Though I did make a few small changes…

The included power supply was a bit weak, and the motion trigger electronics would lock up whenever the head-oscillating motor kicked in.

Rather than try to explain to tech support, I just ordered a beefier 6V 3A 5.5x2.1mm tip-positive power supply on Amazon for about $7. Werewolf runs fine now.

Looking up the werewolf’s neck into its skull, we can see the eye electronics are self-contained in two small boxes joined by a flat flex cable. Mounting screws are inserted from the outside, so it seemed necessary to peel back the fur and rubber skin to remove these. Some glue was cut around the perimeter of the eyes, where the skin meets these boxes.

Eyes removed from the skull, then popped free of their housings.

As it turned out, the the enclosures are snap-fit, so it is possible to access the electronics without all the above disassembly…just remove them from the back, keeping the skull and skin intact.

The eyes are both yellow in person…it’s normal with low-cost TFT screens that the colors shift a bit when viewed off-angle, as is happening here.

The silver Sharpie marks are my own notes, so I can reassemble this later.

First there’s two 1.8" 160x128 pixel TFT color displays…a nice boost from the 128x128 pixels of our earlier eye projects. Possibly ST7735, or something similar…not too important, most small displays function very similarly.

Around $1-2 each in large wholesale quantities…probably the most expensive component of the eye electronics.

One display just has a passive adapter PCB with some connectors, while the other contains all the smarts…

The microcontroller was the hardest part to characterize. An AC19AP1Y201-13C1, which I eventually traced to ZhuHai JieLi “Jerry” Technology.

Couldn’t find more info as it’s not shown in their current lineup…but considering their most recent offerings with Bluetooth or WiFi support are around $1, and if the eyes work the way I think, this is probably a barebones 32-bit MCU at a fraction of that cost.

At least I could find a datasheet for the external flash, an XMC XM25QH16BZ16 — 16 megabits (2 megabytes) with single/dual/quad SPI interface. Couldn’t find a price, but a similar chip from Winbond is about 30 cents.

More interesting here is the red dot. This is a strong hint that all these “LifeEyes” creatures — the werewolf, skeleton and dragon — are using identical hardware, and each just has a different preprogrammed flash chip with that creature’s graphics. Red dot = werewolf. Maybe it corresponds to the red flannel shirt that all werewolves are required to wear.

Remainder of the PCB is connectors and passives. Looks like power regulation at the bottom right, and TFT backlight driving at the top left. A few unpopulated pads that probably weren’t needed in the final design.

I was hoping there might be a couple secret jumper pads to unlock other features (like on the Tiny Arcade retro games), but no such luck here. It has one job.

Using an oscilloscope to listen in on some signals was sufficient for a theory of how it works. This focused on one of the display connectors, and the flash chip.

Also, just looking at the screens as it worked…

For example, it’s easy to spot that the exact same image is being shown on both displays. The signals are simply split and sent to both connectors.

In our two-eyed projects, each is controlled separately, there are distinct left/right eyes…they have a particular shape, and they “fixate” — slightly crossed, as eyes normally do in reality, to focus on nearby subjects.

Here they’ve cleverly approximated fixation by making the plastic housings distinct for left and right, creating a physical stencil of the larger eye image.

It becomes even more apparent as you watch it run. You can’t fit many frames in 2 megabytes, but they make good use of them. The eye only moves between five positions, always returning to the “home position” between moves. Never blinks or dilates when in motion, only at those locations. And the blinks and dilations are always symmetrical — the frames going into a motion match the frames coming out of a motion, just in reverse. The pattern repeats after about 15 seconds.

In practice though…while that would be a neat hack, and I’m sure someone will do it…very few readers will have the tools and methods to follow along at home, so I ended the exploration there.

It would be significantly easier (and also better looking) to simply swap out the eyes for a MONSTER M4SK board, which can then be customized with your own graphics over USB. We’re done this exact thing in several other guides, so it’s easy to follow along!

It’s pretty clever though. My only disappointment is that the eyes look so basic. With pre-rendered frames and no realtime computational bottleneck, the eyes could have looked phenomenal, all smooth and antialiased and richly detailed, had someone just put in the work.

The manufacturer, Seasonal Visions International, has a U.S. office in Emeryville, California, a stone’s throw from Pixar. I mean literally…step out front, throw a stone, hit Pixar. You’d think they could bribe someone with a case of craft beer or something.

I see some parallels with last year’s Speak & Spell reboot. While this could’ve used the original’s exact voice — the code’s out there to emulate it — instead there’s just a large flash chip of newly-recorded spoken audio samples.

It’s disappointing from a technology purist’s perspective…but on the flip side, they had to balance being a nostalgia product while simultaneously a modern educational product where people expect affordability and higher voice quality now. Engineering is expensive. Not much of a technical hack, but a good dollars-and-cents hack. Both are valid.

This Digi-Eyes Mask (Party City, Walmart, etc.) retails for $16.97 + tax, and that’s including a set of AAA batteries that are already flat and leaking.

Like the famous Home Depot Giant Skeleton, this plastic skull mask has my roommate’s eyes staring back at me, so we already know there’s some technological DNA in common with the prior products.

A quick look inside the battery box first, because I was intrigued by the speaker grille. Does this make noise? It does not. Most likely, a generic box is being used across many products. The tooling for molds is astoundingly expensive, so it makes sense to use the same box everywhere, whether or not a particular item includes a speaker. Cheaper by the dozen million.

A small PCB holds the power switch, connectors and an unmarked 8-pin IC: almost certainly a 555 timer for the “Try me!” feature.

Three screws join the mask and “eye box,” which incorporates forehead support and the bridge of the nose.

Easily moved to another mask or prop if desired, or pop into Jack o’ lantern…if that’s not already a product from the same company.

Familiar guts inside the eye box, at first glance appears identical the werewolf: driver board, ribbon cable and two budget low-contrast color LCDs. The screens are rectangular (160x128 pixels), but “stenciled” through round cutouts in the enclosure.

This board too uses a mysterious “Jerry” microcontroller. But it’s not identical. You’ll notice there’s no flash chip this time, knocking about 30 cents off the bill of materials. On the LifeEyes™ props, the whole eye animation cycle was pre-rendered in that flash chip. Without the chip, what’s up?

I couldn’t locate this exact JLT chip in the current lineup, but from other products there we might infer a reasonable amount of program flash space, perhaps 256K. Not enough for a whole animation as with the Winbond flash chip, but sufficient for a single large image alongside the code.

Home Depot stepped up their werewolf game this year with a much larger 9.6 foot model…sort of a cross between their prior 7 foot guy and the famous 12 foot giant skeleton. Of course it still has the red flannel as required.

Image credit: Home Depot

Eye modules (conveniently labeled left and right) come out easily with two screws each.

And with the eye cutouts in the werewolf’s head, we can see the “stencil effect” is in full force. As we’ll see later, when the eyes are open they don’t even have to draw eyelids.

From the front, we can see the bitty 160x128 screens of the smaller props are upgraded here to common 320x240 displays…forgot to measure while they were out, but probably 2.4 or 2.8 inches.

Since these big props go out in the yard and not under a porch covering, the electronics are fully enclosed and sealed with what looks like polyurethane glue. Decided not to compromise the seal for further teardown…we can tell well enough from the animation and from this edge glimpse of the electronics that all the same principles are in use, just more pixels.

The animation leans on techniques from the earlier props…the motion is all “on rails,” with blinks and movements following a set path and returning to a home position.

When fully open, eyelids aren’t drawn, relying instead on the plastic outer shell to provide a stencil. So there’s probably not even run length encoding being used to save flash space, just full raw frames as with the earlier props.