[0:00] I got this 2x2 meter 400 LED curtain. I’ll do a quick run through of it, but we’re not
[0:06] here to do a review. We’re here to take it apart and see how hackable it is.
[0:10] There are a whole bunch of built in patterns that you can control with the remote and there’s
[0:14] an app that connects to it over bluetooth. I have had a look at the bluetooth characteristics
[0:19] but as is typical with bluetooth devices there’s no way to know what they mean or what values
[0:24] to put into them, which is a shame. Let’s take it apart and see how it works, then we’ll
[0:28] see if we can hack around with it. So there’s something pretty interesting about these LEDs.
[0:34] Let’s just start off with the power supply. So it’s a 5 volt 3 amp power supply, that’s
[0:39] pretty beefy. If we unscrew this then we can pull this apart and you can see it’s keyed
[0:46] so we can’t plug it in the wrong way round, which is good because that’s the kind of thing
[0:51] I would definitely do. Now if we follow the power cable round, so I’ve got it all rolled
[0:59] up here so it doesn’t get tangled up, then we can see it just ends up being spliced into
[1:06] the main cord and it’s just joined in and then we have these three wires going off to
[1:12] the control. And then coming out we have three wires, so one of these will be power, one
[1:19] of them is ground and one of them is the data line to drive the LEDs. Now each strand of
[1:25] the LEDs, they just tap off three wires, so you can see a strand here and that just taps
[1:33] off from the main cable, goes to all the LEDs and then it’s just cut off at the end. So
[1:40] we just have three wires going through here as well. And then the next one is the same,
[1:46] so it just taps off the main cable, three wires are just tapped off, going down the
[1:54] next strand. So that’s pretty interesting. Now you’re probably asking, why is this interesting?
[2:01] Well normally with addressable LEDs you need to daisy chain them together. They have four
[2:06] pins, two for the power and then a data in pin and a data out pin. You feed the data
[2:12] into the in pin of the first LED and it then drives the next LED and then that drives the
[2:17] next LED and so on. This is how the LEDs know what to display. You feed all the data into
[2:23] them serially and then once you’ve finished sending all the data, each LED just locks
[2:27] in the last serial data it received. For an LED matrix you normally need to link the end
[2:33] of each column or row of the LEDs to the next column. So for an LED curtain you would either
[2:38] expect them to be joined at the bottom or to have a return wire for the last LED in
[2:43] the column. With this LED curtain the data line is actually a bus and all the LEDs are
[2:48] connected in parallel to it. This means that the LEDs receive the entire data stream. The
[2:54] LEDs need to be pre-programmed with their position in the string so they can pick out
[2:58] the data that is relevant to them. It’s very clever stuff. I have found a great thread
[3:03] on the doubly led GitHub repo where these pre-addressed LEDs are discussed. They got
[3:08] some nice close up shots of the actual LEDs and a good discussion on how they work. I’ve
[3:13] put a link in the description. So that’s the LED strands with all these little LEDs encased
[3:19] in some kind of epoxy. Not sure what. So let’s have a look at the control thing. So there’s
[3:30] a clicky button and it’s quite easy to take apart. We just undo these screws. I’ll use
[3:36] the wrong screwdriver. So let’s just get these out. That’s one screw, the next screw. That’s
[3:45] our four screws. That’s already come off. So here’s our PCB. You can see the IR receiver.
[3:55] I’ll take a proper photo of this and we’ll do a bit of reverse engineering and see how
[4:00] it works. But let’s finish getting this open. So I think this will just pop off as well.
[4:05] It just seems to be sealed on with some silicon. So we can get that off. And then we’ll be
[4:15] able to extract the PCB completely. Ok, that’s that off. Lots of silicon. Nice. There’s the
[4:26] wires going in. Let’s see how we can get this out. I’d quite like to not destroy this because
[4:32] we do want to put it back together again at some point. But it’d be nice to get it out
[4:38] and just see if there’s anything on the other side of the PCB. There we go. Excellent. So
[4:52] hopefully we loosen some of this. There, free. So what I do want to do eventually is desolder
[5:05] this but let’s have a look at some of the signals first. So I’ve plugged everything
[5:10] in and I’ve got my multimeter. So as far as I can tell, this middle pin seems to be ground
[5:17] and that’s our 5V supply. And we’ve also got the same on this end, so ground and 5V. And
[5:28] then this pin here must be the signal pin. So let’s hook up our oscilloscope and see
[5:32] what that looks like. And I’ll just hook my crocodile clip to there. And then we should
[5:41] be able to just probe there. With a bit of luck. I can get my ground connection to actually
[5:52] connect. So rather than try and film the oscilloscope screen, which I never seem to get a good picture
[5:58] from, I’ve just taken a screenshot. So what we can see here is we can see the data being
[6:03] clocked out to the LED matrix. So we can see the data, then there’s a gap and then more
[6:09] data. So what happens during the gap is that’s when the LEDs detect, there’s no more data,
[6:14] and they latch in the current display. And then it just repeats itself and that’s how
[6:18] you get the animated frames. So that’s pretty cool. Let’s have a look at the PCBs in close-up.
[6:25] I’ve cleaned off most of the silicon and taken some nice close-up photos. There’s actually
[6:29] not much on the back of the board, but it is nicely labelled. Let’s have a quick look
[6:33] at the components on the front of the board. There’s a 3.3V regulator here which powers
[6:38] the main IC, an ST17H66B2. This is a Bluetooth low energy system on a chip. The antenna for
[6:46] the Bluetooth is this PCB trace here. To actually drive the LED string, it’s using this buffer
[6:52] IC to level shift the 3.3V output back up to 5V. The resistor here is just a 0 ohm link
[6:59] and the blank space next to it allows them to bypass the buffer IC completely. So it’s
[7:03] possible that for smaller LED curtains, the buffer chip is not needed. Hopefully this
[7:08] also means that the LEDs will operate at 3.3V and we won’t need a level shift of ourselves.
[7:14] Over here we’ve got the IR receiver and I believe that this area here along with the
[7:18] microphone is for the audio responsive mode of the curtain. That’s kind of it really.
[7:23] Pretty simple. Let’s have a go at driving it ourselves from an ESP32. On the subject
[7:29] of PCBs, now’s a good time to mention PCBWay who are sponsoring the channel. I’ve got a
[7:34] couple of PCBs with them right now. I’m waiting on my new ESP32 TV board to come back. Really
[7:39] excited about it and if you want some PCBs, have a look at PCBWay. They’re really good.
[7:44] So I’ve flashed WLED onto this ESP32 and I’ve just crimped some header pins onto the wires.
[7:54] We can just power this from the 5V power and it seems to work so we’re connected up. Let’s
[8:01] try changing the colours. That seems to work nicely. We can go all the way around the colour
[8:09] wheel. Let’s have a look at the effects. I’m not sure what any of these really do. Blink.
[8:15] I guess that blinks on and off. Very exciting. Blink rainbow. Blobs. So this is quite nice.
[8:25] It seems to be working off 3.3V. What I’ll do is I’ll get this laid out on the floor
[8:31] so we can actually see what it’s doing and see if the grid’s actually working. So one
[8:36] moment. Okay, so I’ve got it laid out on the floor and I’m connected through to the WLED
[8:42] Wi-Fi interface so we can try a few of the grid patterns. So that is black hole. This
[8:50] is called blobs. Colour bursts. That’s quite nice. Crazy bees. Distortion waves. Interesting.
[9:05] This is supposed to be DNA. I quite like that pattern. That’s quite nice. DNA spiral. That’s
[9:11] pretty cool. There’s something called drift. Interesting. Let’s see. Fireworks. Doesn’t
[9:21] seem to do very much. Fireworks 1D. There we go. That’s pretty nice. So I do like this
[9:31] WLED software. It’s pretty cool. Very impressive. Let’s see what else we have. Hiphotic or hyphotic.
[9:43] That’s a pretty nice pattern. I like that. That’s very cool. We have a lissajou. Looks
[9:51] kind of like the DNA. And of course we have the matrix effect. That’s quite a cool effect.
[9:57] I like that. And something called octopus. There’s an absolute tonne of these. So I recommend
[10:04] checking out WLEDs if you get yourself a LED curtain. Very cool.