Sonoff S26 pogo-pin flash adapter

I bought a couple of Sonoff S26 Wifi-plugs. These are built with an ESP8266 wifi chip and can be programmed with custom firmware.

I wanted to flash them with Tasmota firmware and didn’t want to solder wires to every one,  so I made a pogo-pin flash adapter 🙂

I built it to be used with my FTDI USB to TTL Serial converter. The one I got, have 3.3V pins for communication(RX/TX, etc) and 5V for power. The ESP8266 chip needs 3.3V for both power and GPIO’s so I designed the flash adapter to contain a voltage regulator (FTDI 5V -> Voltage regulator -> 3.3V Sonoff ESP8266).

This features:

  • Solderless flashing of Sonoff S26
  • Easy to use
  • Power ESP from USB
  • FTDI USB to 3.3V Serial TTL cable – compatible.

Whats needed:

  • 3D-printed parts, STL’s can be downloaded from my Thingiverse.
  • Pogo-pins, P100-E2, Diameter: 1.36mm, Length: 33.3mm.
  • Voltage regulator, HW-108, 20x20mm.
  • FTDI or similar, USB to TTL 3.3V Serial cable.
  • Sonoff S26 Wifi plug.
  • 3pcs small screws for the top lid.
  • 6pin – pin-header.


  • I take no responsibility if you build this or use this!
  • Use it at your own risk!
  • Never plug the Sonoff S26 in to mains power when you have take it apart!

Build it:

  1. Print the needed parts.
  2. Attach pogo-pins.
  3. Solder wires to voltage regulator. (If you have a USB to TTL serial cable which can supply 3.3V, you can skip the voltage regulator and solder wires for 3.3V and GND directly from pin header to pogo-pins and skip step 4).
  4. Solder voltage regulator wires (5V and GND (IN) to pin-headers and 3.3V and GND (OUT) to pogo-pins).
  5. Solder wires for RX and TX to pogo-pins and pin-header.
  6. Check all connections and make sure everything is correct.
  7. Attach FTDI-cable and adjust output voltage from voltage-regulator to 3.3V.
  8. Use some hot glue to hold pogo-pins and pin-header in place.
  9. Attach the lid.
  10. Finished! Time to flash 🙂
The finished Sonoff S26 flash adapter
The flash adapter connected to one Sonoff S26.
ESP8266 Chip in the Sonoff S26
Flash adapter with side open, header pinout.
Flash adapter pinout.

How to use the flash adapter:


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