Hardware teardown: the Logitech Harmony Hub

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Geert

Hardware engineer

29 Sep  ·  5 min read


We’re continuing our series of hardware teardowns! This month, we tackled (or more accurately, dismantled) the Logitech Harmony Hub, a device that aims to unite your connected home.

Logitech’s Harmony Hub is a smart hub that can connect all sorts of domotics and smart devices in your home (entertainment devices, sound systems, smart locks, blinds, and more) and lets you control them all from the Harmony app on your smartphone. A nice concept (retailing for a RRP of $99,99) – so we decided to pry open the shiny black casing and take a look at this little box’s guts.

Let’s get started!

I used a number of basic tools to take the device apart: a cutting knife, screwdriver, and a USB microscope.

I started by taking a look at the contents of the box, which contained six parts: the Harmony Hub itself; an IR blaster; a micro-USB cable; a charger; and two modular plugs, one European and one American.

Contents of the box

Next step: opening the hub! Looking at the device from the outside, there are no visible screws – no obvious way to open the casing.

Bottom of case

I guessed that there were some screws hidden under the rubber pads on the bottom of the device, so I removed them with a utility knife. As expected, I found screws to undo the casing underneath, but to my surprise, I also discovered two openings for possible connectors (more about them later).

Bottom case exposed

I grabbed my screwdriver and removed the screws. After that, I tried opening up the case, but it was still stuck because of some plastic retaining clips around the edge. We didn’t have a plastic opener lying around, so I used my cutting knife to carefully pry the case open.

Weight

I removed the PCB to study closer, and immediately noticed something about the case itself. There is a weight attached to the bottom part of the casing to give the body of the hub a little more weight. It’s an often-used product design trick, used to make the product feel more solid and durable, and to give you the impression of quality. That’s not to say that this product is not of high quality, though! The connection many people subconsciously make between physical weight and quality doesn’t necessarily hold with electronics. On the top of the casing, you can also see a few thinner spots in the plastic shell, where the IR LEDs can shine through.

Case plastic lights

A closer look at the PCB

Case opened

After inspecting the casing, we obviously turned to the most interesting part of this little box: the PCB. Firstly, I noticed that the PCB is not of a standard thickness: it measures only 0.9mm in thickness, instead of the usual 1.6mm. I’m honestly not quite sure why Logitech went with a smaller thickness, although I doubt it was only for those 0,7mm saved in space.

Thin pcb

The bottom of the PCB shows us some testing points which are labelled on the silkscreen layer with TPXX. These were also present in our previous teardown. This indicates that Logitech uses a (semi)automated testing setup, which every decent hardware manufacturer has these days.

On the bottom of the PCB you can also find two big IC’s, two 2.5mm IR mini blaster ports (marked in blue below), a micro USB port (marked in yellow) and a reset/pair button (marked in green).

Bottom pcb

The first IC, marked in red on the picture above, is the EM6AB160TSE-5G: a 512 Mbits SDRAM chip manufactured by Etron Technology. The other IC, marked in orange, is our main controller and is the AR9331, a 2.4 GHz 802.11b/g/n SoC for Access Point and Router Platforms manufactured by Atheros. You can also see two header locations, titled J2 and J3, on the right side of the board. What J3 is used for is a bit of a mystery, but J2 is used as a serial connection for the AR9331 IC. I personally think they’re both there for support purposes. When the unit is sent back under warranty, it would be easier for the support guys to see what’s wrong by simple removing the right bottom pad and connecting a serial monitor to it, without having to open up the whole device.

I also had a bit of a laugh at how the ICs are placed: they look like they’re almost aligned – just the littlest bit off. Likewise, the small SMD resistors and capacitors are placed in a not-very-aligned manner.

On the top of the PCB we can see six IR leds (marked in orange below), three IC’s and three antennas. The antenna marked in light blue belongs to the AR wifi chip on the bottom of the PCB. Also note the black sticker on the top of the board: it’s used to stop the light from the status LED on the back of the PCB showing through the top of the casing, which would cause confusion.

Top pcb

The first IC, a CC2544 (marked in yellow above), is a Single-Chip 2.4-GHz RF Transceiver and MCU, with an RF antenna attached. This chip is manufactured by TI and is a frequently used chip in a lot of RF devices. The second IC is the MX25L12835F (marked in dark blue) which is a 128MB serial Flash memory chip manufactured by Macronix. We assume that this memory is used to store user and device configurations. The third IC is the CSR8811 (marked in green). It was initially hard to identify, but is a single-chip radio and baseband IC for Bluetooth 2.4GHz systems, including enhanced data rate to 3Mbits/s and Bluetooth low energy. The chip, manufactured by CRC (which was acquired by Qualcomm in 2015), is designed to reduce PCB area and the number of external components required. We can also see that the PCB is manufactured by a Chinese company called FCF.

And with that, we can wrap up our second teardown! Much of the Harmony Hub’s “magic”, of course, happens on the software side of things – but we’re always glad to see what insides are backing it up. We hope you found it interesting, and feel free to reach out on Twitter or Facebook to let us know what you’d like us to dismantle next!


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Geert

Hardware engineer

29 Sep  ·  5 min read