Bits of Cents posted an interesting teardown of the new Amazon Dash Button. We saw the announcement for these when they came out and were curious, expecting them to be based on a low cost Bluetooth Low Energy SoC like the nRF51822. Surprisingly, it turns out they’re based on the more expensive WICED WiFi platform from Broadcom!
In this particular case it seems to be using an STM32F205 MCU with a Broadcom BCM43362 radio and 16mbit external flash, which follows one of Broadcom’s reference designs very closely. That’s 120MHz of ARM Cortex M3 processing power and about $6-7 in parts in volume for a button and an LED(!), compared to $2 for a BLE SoC, though WiFi does lower the HW requirements outside the device since almost everyone has WiFi access at home, whereas BLE tends to still be found mostly in flagship mobile phones or higher end laptops.
Looking at the high-res (though unfortunately not very crisp) photo of the top of the PCB, you can see:
- U5 – STM32F205 120MHz ARM Cortex M3 MCU with 128KB SRAM and 1024KB Flash in a WLCSP64+2 package
- U9 – Broadcom BCM43362 Radio
- U6 – 16MBit SPI flash (for firmware updates)
- J1 – Looks like an SWD/JTAG connector!
There are a lot of test points on this board, and with the tempting connector this looks like it might be supremely hackable!
The back of the PCB looks like this:
That looks like a TI low startup voltage boost just above the battery (that’s a fairly common footprint for them with the two little leads coming off the thermal pad underneath but it’s hard to make the text out), though the inductor looks like it was ripped off during separation (L1). The tin can to the left of the AAA cell is most likely a MEMS microphone, which is what they use to configure the wifi (via audio signals). That might explain the need for a bit of processing power, but it’s definitely a far more expensive device than any of us expected!
We’re waiting to get our hands on one, but if this is as hackable as it looks, DASH could turn into a great starting point for a lot of of interesting WiFi-enabled projects!
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