Alex Momchilov

Staff Engineer @ Shopify

My beloved Ubiquiti SmartPower Plug (USP-Plug-US) died about a year ago. Now that it’s out of production (and has almost no mention on Ubiquiti’s site), I took a stab at repairing it. Spoiler, I couldn’t fix it, but I still took some notes, in case they might be useful for other hardware hackers.

For the same $24 CAD I paid for the Ubiquiti smart plug, you could buy 3 or 4 from some obscure brand (with questionable software quality and security). While pricier, I bought the Ubiquiti one for 3 main reasons:

  1. Works locally, even when the internet is down
  2. Integrates with the Ubiquiti network controller
  3. Your Ubiquiti router can instruct it to restart your modem, when you internet lose connectivity for more than a few seconds

Getting in

… is a mess. With a combination of squeezing and prying, I’m fairly sure this is a one-way trip. I missed the memo to desolder the prongs before trying to pull the board out. I broke part of the PCB right off. Welp, it’s a salvage mission now.

Main board

I did my best to annotate the electrical connections. Pretty compact layout, but it’s pretty straight forward. A 3.3V power supply, a button, an LED, and a relay to energize the main relay.

Connecting a programmer

You can connect a 3.3V UART programmer with these 5 easily accessible points:

  • Rx: top-left-most test point
  • Tx: the test point to the right of Rx
  • V+: the big solder blob in the top-right, marked Vcc
  • V-: the blob between Tx and GPIO 0, marked GND

To program the ESP8266 over UART, you need to boot it into serial bootloader mode. You do this by grounding GPIO 0 (the top test point) during start up.

Pinout

Here is the pinout of the edge connector of the the micro-controller board, that’s slotted into the main board photographed above.

It’s as accurate as I could get it, given my chip had a short across Vcc and ground. YMMV.

             
Top - pin   15 13 12 10  
Top - name   GPIO0 GPIO15 GPIO13 GPIO12  
Top - function GND boot_sel Relay Button LED Vcc
             
Bottom - function Tx Rx ? ? ? ?
Bottom - name GPIO1 GPIO3 ? ? ? ?
Bottom - pin 26 25 32 8 14/161 ?

Micro-controller board

Since my plug was already toast, why not tear it down and see what’s under the grounding shield. Lo and behold, it’s a beloved ESP8266!

  1. An ESP8266EX microcontroller (compatable with ESPHome!)
  2. SPI Flash
  3. A 26 Mhz crystal oscillator (FK 26.e9F)

Other resources

  1. This was electrically continuous with both pin 14 and 16. Not sure why. ↩

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