Teardown: Amazon Dash Button keeps you connected

-March 04, 2016

Amazon's Dash Button, which I previously mentioned back in late May 2015, is the ultimate in consumer convenience (or, if you prefer, consumerism gone crazy). Simply press a button on the inconspicuous adhesive-backed device (perfect for attaching to your washer and dryer, refrigerator, counter, or cabinet), and your Amazon account is charged for the purchase while the corresponding product gets automatically ordered and shipped to you.

Initially unveiled on April 1, 2015 (therefore explaining why I at first thought the announcement was an April Fools' joke from the company), they cost only $4.99, and Amazon more recently announced that it'd even refund the purchase price after your first associated-consumable order. How much hardware was Amazon able to squeeze into such a diminutive bill-of-materials budget, or perhaps more accurately, how much are Amazon and its consumable-supplier partners subsidizing the initial hardware cost in the hope of plenty of future generated profits? Let's find out.

To begin, here are some views of the packaging for the particular unit I ordered, which is associated with Gatorade sports drink:

On the last one, you'll note that (for privacy-preservation reasons) I've blurred out both the UPC and alphanumeric sequence associated with my unit's DSN (Dash Serial Number). This code, as its name implies, is device-specific; in conjunction with your pre-configured Amazon account information, it indicates to Amazon's servers what class of product is being ordered (Gatorade sports drink, versus any of the other items on the already-numerous and steadily growing list of consumables that the Dash Button service supports) and who's ordering it.

Still to be configured upon initial product setup are your residence's wireless network SSID and encryption password, and exactly what product you're interested in button-press ordering (Gatorade flavor, for example, and packaging size and quantity). Stay tuned for more details on how both objectives are hardware-accomplished.

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The packaging is Apple-like (or, come to think of it, Amazon-like, keeping in mind past products from the company that I've also used) in its simplicity:

The only thing inside the box aside from the Dash Button itself is a diminutive quick-start guide. Here's what my Dash Button (3.2×1.2×0.6 inches; 1 ounce) looks like after removal from the box:

Note the small LED above the button, used both when initially setting up the Dash Button and subsequently as visual feedback of a successful order submission. Note, too, the mysterious hole above the Gatorade logo, whose function will be explained shortly:

The DSN is replicated on the unit's backside, along with a QR code, both of which I've again obscured:

Perhaps obviously, the foundation hardware for all Dash Button variants is identical; customization occurs via the combination of assembly line-programmable firmware, a consumable brand-specific label applied to the device topside and a device-unique DSN sticker on the bottom. The brand label, along with the plastic outer oblong "ring" surrounding the remainder of the chassis, are easily removed:

Label peel-away reveals three Torx screws underneath:

Removing the screws doesn't, however, enable separation of the two chassis halves; the screws' sole purpose seems to be to hold the PCB inside in place. Cracking open the case is alternatively accomplished via deft application of a screwdriver edge to break the around-the-rim glue bond:

Lift off the bottom half of the case and the first thing you'll see is a lithium AAA battery:

It’s held in place in part by an easily removed plastic piece:

Somewhat surprisingly, the battery is welded to its associated positive and negative terminals, dooming the device it powers to a finite-duration lifetime, since the battery's also not rechargeable (via Wi-Fi scavenging, a micro-USB tether or some other means). Now look closely above the positive terminal of the battery; what do you see?

It's an InvenSense INMP441 MEMS microphone, actually. Recall that the Dash Button requires connection to an owner's Wi-Fi network, but there's no wired Ethernet port alternatively available to send initial configuration data to it. One alternative means of accomplishing this objective, as is also done with products such as the Google Chromecast and Belkin's WeMo switch, involves the device initially broadcasting a wireless network with SSID "Amazon ConfigureMe," to which the Android version of the Amazon Shopping app connects. At that point, accessing the Dash Button's built-in Web server at enables entry of the remaining setup parameters.

The other configuration option is pretty (albeit not completely) unique, and leveraged by the iOS version of Amazon's configuration app (the reasons for the operating systems' setup discrepancy are unclear to me; perhaps Apple doesn't give Amazon sufficient low-level access to accomplish an Android-like Wi-Fi hotspot scheme). In this case, setup parameters are sent via ultrasound from the smartphone or tablet to the Amazon Dash, using the former device's speaker and the latter device's aforementioned MEMS microphone.

With the three screws normally holding the PCB in place removed, the circuit board lifts right off, exposing the underside of the chassis topside:

Visible are the bottom of the "order" button, the translucent diffuser for the PCB-mounted LED, and the previously mentioned hole that mates up with the MEMS microphone. As for the PCB itself, here's an overview photo:

In the very center is the aforementioned RGB LED, labeled DS1. Embedded above it, in the PCB's blank section covered with black marker-handwritten inspection notation (I assume), is the Wi-Fi antenna, which is even more visible via X-ray exposure. And in the upper left quadrant is a Micron Technology M25P16 16 Mbit SPI serial interface flash memory.

Underneath the QR code-embossed sticker to the left of the LED (and to the lower right of the M25P16) is a BCM43362 2.4 GHz 802.11b/g/n Wi-Fi module:

Another perspective of the PCB brings into view the faint markings on the shiny IC below the BCM43362. It's a STMicroelectronics STM32F205 microcontroller:

More generally, the Amazon Dash appears to be based on a Broadcom WICED (Wireless Internet Connectivity for Embedded Devices) reference design module. Combine the Wi-Fi IC and the microcontroller into one packaged device, by the way, and you end up with the USI (Universal Scientific Industrial) WM-N-BM-09 WICED module, which forms the foundation of the $19 Spark Photon development kit.

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