This project is a simple MicroPython program for Itead S20 Wifi Smart Socket. It replaces the default firmware. It allows remote control by using MQTT broker. For example Node-red with embedded MQTT broker node-red-contrib-mqtt-broker can be used as a controller to build automation flows for the device.
The program registers with MQTT broker, subscribes topic and waits for
message with on or off payload. When message is received, the state
of relay switch is set to on or off.
If button is pressed on S20 Wifi Smart Socket, the program will publish
on or off message to the broker.
First, the default firmware on S20 Wifi Smart Socket needs to be replaced with MicroPython firmware. In order to flash MicroPython you'll need USB UART with 3.3V option. Ebay sellers have various options. Check that yours also provide 3.3V TTL level and not just 3.3V output voltage.
Download MicroPython firmware image for ESP8266 from http://micropython.org/download#esp8266
Install esptool flasher into a Python virtualenv
virtualenv esptool-virtualenv
. esptool-virtualenv/bin/activate
pip install esptool
To open S20 Wifi Smart Socket you'll find one screw under the red sticker at the back of the device. After unscrewing it, pry the cover open carefully from the sides. There is only single clip holding the cover at the bottom, so it is easiest to start there.
When the cover is open locate the pads marked in the figure as GND, TX, RX and 3.3V:
To program the microcontroller you can either solder pin header to the PCB or just solder wires directly. Yet another alternative is to build a cable with pogo pins to create temporary connection:
Connect USB UART to the 3.3V, GND, TX and RX pins:
Keep reset button (the button in the middle of the PCB) pushed to enter programming mode while connecting USB UART to the device to enter the programming mode. You can release the button after the device has been powered. Then execute:
$ esptool.py --port /dev/ttyUSB0 erase_flash
esptool.py v2.1
Connecting....
Detecting chip type... ESP8266
Chip is ESP8266
Uploading stub...
Running stub...
Stub running...
Erasing flash (this may take a while)...
Chip erase completed successfully in 2.4s
Hard resetting...
Disconnect the programmer and connect it again while again pushing the reset button to enter programming mode. To flash micropython image run:
$ esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect 0 ~/Downloads/esp8266-20170823-v1.9.2.bin
esptool.py v2.1
Connecting....
Detecting chip type... ESP8266
Chip is ESP8266
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 460800
Changed.
Configuring flash size...
Auto-detected Flash size: 1MB
Flash params set to 0x0020
Compressed 601136 bytes to 392067...
Wrote 601136 bytes (392067 compressed) at 0x00000000 in 8.8 seconds (effective 546.4 kbit/s)...
Hash of data verified.
Leaving...
Hard resetting...
Disconnect the programmer and connect it again but do NOT push the
reset putton this time. Use serial terminal emulator program such as
miniterm which you should have now installed in esptool-virtualenv
(part of pyserial which was installed as dependency of esptool).
After launching terminal emulator press enter to get python prompt >>>.
$ miniterm.py --raw /dev/ttyUSB0 115200
--- Miniterm on /dev/ttyUSB0 115200,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
#5 ets_task(4020edc0, 29, 3fff9150, 10)
OSError: [Errno 2] ENOENT
MicroPython v1.9.2-8-gbf8f45cf on 2017-08-23; ESP module with ESP8266
Type "help()" for more information.
>>>
To get S20 Wifi Smart Socket to join to your Wifi network at boot you must connect wifi network at least once. ESP8266 will store the connection information into EEPROM and use it each time when rebooting to reconnect.
Enter paste mode by pressing CTRL+E in MicroPython prompt and copy & paste following code:
import network
sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)
sta_if.connect('MYSSID', 'MYPASSWORD')
Change MYSSID to your wifi network name and MYPASSWORD to your wifi password. Print the IP address your device got from your network by running:
sta_if.ifconfig()[0]
WebREPL is a method to use the Python prompt remotely via a web socket. This is much more convenient way for trials and development than using serial console, especially if you did not solder header pins to the S20 Wifi Smart Socket to get permanent USB UART connection.
To set WebREPL password, execute following in Python promopt while still being connected with serial console:
>>> import webrepl_setup
WebREPL daemon auto-start status: disabled
Would you like to (E)nable or (D)isable it running on boot?
(Empty line to quit)
> e
To enable WebREPL, you must set password for it
New password: NNNNNN
Confirm password: NNNNNN
Changes will be activated after reboot
Would you like to reboot now? (y/n) y
This password will be prompted from clients who connect WebREPL server via network.
To connect your device over the network you can use WebREPL client in
web browser. You can access it here http://micropython.org/webrepl/.
It requires the IP address and port of the WebREPL server running in
S20 Wifi Smart Socket ws://YOUR_IP:8266/ where YOUR_IP is the
address that the if_config() call returned.
Alternative method for the browser based WebREPL client is mpfshell. Install by running:
pip install mpfshell
Then connect to the WebREPL server by running:
mpfshell ws:YOUR_IP,password
Connect to the webrepl and write following code to the Python prompt:
from machine import Pin
relay = Pin(12, Pin.OUT)
relay.on() # turn power on
relay.off() # turn power off
If the device is only powered by USB UART you will not hear the relay click, but you will see the LED lit.
First modify the configuration in config.json with your MQTT broker
address, username, password and topic. Next upload the program and the
config file:
mpfshell "ws:YOUR_IP,password"
put main.py
put config.json
After rebooting the device, the program will establish connection to MQTT broker. The connection between device and broker is not secured by TLS and the intention is to use the program with broker in trusted network only.
[1] S20 Wifi Smart Socket Schematic https://www.itead.cc/wiki/S20_Smart_Socket