Tasmota: Sonoff Slampher WiFi Bulb Holder Local Control

This guide is a part of Domoticz Tasmota: Control Sonoff without Internet and Yeti Tasmota: Control Sonoff without Internet Instantly which require firmware modification by upgrading official Sonoff firmware to opensource Sonoff Tasmota firmware. By installing Tasmota firmware, We’ll be able to achieve local control of our WiFi Bulb Holder without internet.

Let’s have a look on the whole process briefly. First We’ll prepare our Sonoff Slampher to make it ready for connecting it to our computer. Secondly, We’ll back the original firmware up and upload Sonoff Tasmota firmware using our computer and serial adapter. In last, We’ll configure our new firmware a little bit and our WiFi bulb holder will be ready to be hooked to it’s final place.


Sonoff Slampher Firmware Modification:

Note: Always unplug the Sonoff device from AC Power Source before start working with it.

Step A – Dissembling:

Unscrew the two screws found on the rear side of Sonoff Slampher using screw driver and lift the upper lid. Take the PCB out carefully without pulling the wires connected to it.

Sonoff Slampher Dissembling

Step B – Programming Mode:

Install a male or female header on holes given for programming the device by soldering it permanently for a firm connection. Header without soldering will result in loose connection and uploading may fail.

The Sonoff Slampher have an 8bit EFM8BB10F2G-A-QFN20 microcontroller that listens to the radio module messages and handles the on-board button tied to GPIO-0. However, it can not be used to enter Sonoff Slampher into programming mode. For starting Sonoff Slampher in programming mode GPIO-0 should be tied to ground. For this purpose, solder a small piece of wire to ESP8285 side of resistor R9 which is directly connected to GPIO-0.


Sonoff Slampher Modification to start in Programming Mode


Let’s have a look onto programming header pinout. First pin which is near the 3V3 printed on PCB, is VCC followed by RX, TX and GND. Connect FTDI according to the following combinations.


FTDI Sonoff Slampher
3.3V VCC


Sonoff Slampher Programming Pinout


Connect the wire solder on resistor R9, to GND and Plug the FTDI in to PC. Now micro-controller present in our Sonoff Slampher i.e. ESP8285 will start in programming mode.


Sonoff Slampher FTDI

Step C – Upload Firmware:

Backup official firmware by following our guide Backup & Restore Official Firmware of Sonoff WiFi Smart Switches  under Backup / Download Official Firmware section. After backup, download Sonoff-Tasmota Firmware and upload it according to Upload Official / Third Party Firmware.

Step D – Firmware Configuration:

By short pressing on board button four times, Sonoff Tasmota Firmware allows booting up Sonoff Smart Switches into Wifi Manager Mode providing an Access Point with IP address to configure WiFi credentials. However, the case is different with Sonoff Slampher. As we already know that 8bit EFM8BB10F2G-A-QFN20 microcontroller handles the on-board button tied to GPIO-0, so we cannot start Sonoff Slampher into pairing mode by pressing on board button.

Note: Do not plug Sonoff Device to AC Power Source

During firmware upgrade, we started Sonoff Slampher into programming mode using a short wire connecting resistor R9 and GND. The very same procedure will be followed here to boot the slampher in to WiFi Manager Mode. Touch the wire to GND four times quickly and repeatedly and Sonoff Slampher will boot into Wifi Manager Mode.

Now a new Access Point will pop up under available WiFi networks with the name of sonoff-XXXX (Where XXXX is any number). Connect to this new sonoff-XXXX network and configuration page will open in your browser. If it does not open into your browser automatically, open to into your favourite browser.

Connect Sonoff Slampher to your WiFi network according to Configure WiFi Network Settings under Sonoff Tasmota Firmware and configure MQTT parameters by following the instructions given under Configure MQTT Settings under Sonoff Tasmota Firmware. Now Sonoff Slampher can be accessed by visiting the IP address assigned to it by your WiFi router. Consult your router documentation on how to find the IP address of connected devices. You can also assign a static IP address to your Sonoff device by following instruction given under Set Static IP Address under Sonoff Tasmota Firmware section. By default web page access to Sonoff Tasmota Firmware is open and anyone connected to WiFi network can access to it. Let’s secure web access page by setting up Web Admin Password according to Configure Web Admin Password under Sonoff Tasmota Firmware. Change the module type according to Configure Module Type under Sonoff Tasmota Firmware otherwise Sonoff Slampher may not work as expected.

Now You have completed almost all necessary configuration of Sonoff Tasmota. You can also set default Power on State which will be followed on Sonoff device restart, among ON, OFF and KEEP according to Configure Power On State After Boot Up. Correct Timezone and NTP Server configurations are necessary for timer related functions. However, It is recommended to configure NTP Server and Timezone according to instructions given in Configure NTP Server and Timezone.

Step E – Reassembling:

Now our Sonoff Slampher is ready for the work. Desolder the wire connected to resistor R9 carefully. Reassemble Sonoff Slampher by sliding the PCB inside the enclosure taking care of push button correctly placing in it’s hole. Now put on the lid and tighten the screws back. Plug the Sonoff Slampher into socket and voila!!. You can toggle the light ON & OFF by visiting the IP address assigned to Sonoff Slampher by router. But the smarter way to toggle a switch is discussed in our guide Domoticz Tasmota: Control Sonoff without Internet. Navigate to Step E – Connect & Control the devices to proceed further if you are already following the steps in our guide Domoticz Tasmota: Control Sonoff without Internet.

Step F – RF Remote:


Quickly press the Sonoff Slampher button twice. Red LED will blink once which means Sonoff Slampher is ready for pairing RF Remote. Press and hold desired RF Remote button for couple of seconds and particular RF Remote button will be paired with Sonoff Slampher. Now you can use the RF remote to switch the Slampher ON and OFF as desired.

Erase all Paired Buttons:

Quickly press the Sonoff Slampher button thrice. Red LED will be turned ON for few seconds and known RF code will be erased.

Now you can also control your Sonoff S20 directly using Yeti Smart Phone app. There is no need to establish your own Raspberry Pi server as Yeti connects to your Sonoff S20 directly using WiFi network. Follow our guide Yeti Tasmota: Control Sonoff without Internet Instantly for step by step procedure.

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Do you know if it is possible to decouple relay operation from RF signal. I think in tasmota for exmaple in a configuration with a button you can have two toppics realy and button so pressing button does not switch the realy. Do you know if such a thing would be possible with this device?


@chuck, you say you have a soldered connection between R9 and gnd. Do you separate R9 from Gnd after the reboot?

Chuck Connors
Chuck Connors

Hi. Thanks for posting this. I put this together yesterday and could not get esptool to connect. I’m guessing that it was not seeing GPIO-0 tied to ground. I made the connection you illustrated with R9 on the chip side and tied to ground at the header pins I soldered on. I test continuity from the other side of the resistor and the header ground and it indeed was connected. I checked voltage at the header pins and had about 3.2V . I double check TX->RX and RX->TX and even reversed them to be safe and it still did not… Read more »


I’d like to ask where is the other end of soldered wire from R9 going to? Is it going to the GND of FTDI, GND of the four flashing pins (VCC, RX, TX, GND), or is it going to GND near C20 / R22 ? Thank you very much!