The Espressif Systems ESP8266 is used in cheap WiFi modules. It embeds an Xtensa LX3 CPU. ESP8266 boards named ESP-XX come with at least 1/2 megabyte of SPI flash for program storage.

ESP-01

U0TXD    2 1 GND
CHIP_EN  4 3 GPIO2
EXT_RSTB 6 5 GPIO0
VDD      8 7 U0RXD

Component side with antenna to right

A well regulated power supply is suggested. An LD1117 3V3 has been tested and works well.

3V3 ---------- VDD
3V3 ---10K---- CHIP_EN
GND ---------- GND

The default AT firmware can be updated using ESPTool.

To program the chip, keep GPIO0 low and reset the device on EXT_RSTB.

wget "https://wiki.kewl.org/downloads/v0.9.2.2 AT Firmware.bin"
esptool.py --port /dev/ttyUSB0 write_flash 0x000000 "v0.9.2.2 AT Firmware.bin"
Connecting...
Erasing flash...
Writing at 0x0007ef00... (100 %)

Leaving...

The updated AT firmware uses 9600 baud by default, the original is 115200.

3V3 UART       ESP-XX
========       ======
RX  -- 470R -- U0TXD
TX  -- 470R -- U0RXD
GND ---------- GND

picocom -b 9600 --omap crcrlf /dev/ttyUSB0
AT+RST
...
[System Ready, Vendor:www.ai-thinker.com]
AT+GMR
0018000902
OK
AT+CWMODE=1
OK
AT+CWLAP
+CWLAP ...

The commands above reset the device, set its mode of operation and scan for access points.

NodeMcu is a LUA interpreter than runs on the ESP-XX chip. It can be used to communicate over the network and control the GPIOs.

We will use ESPTool to install NodeMcu for esp8266.

git clone https://github.com/nodemcu/nodemcu-firmware
git reset --hard fb967dd8a2c8282e146626642bf24e8c90cdbcd0
cd nodemcu-firmware/pre_build/0.9.5
esptool.py --port /dev/ttyUSB0 write_flash 0x000000 nodemcu_20150127.bin
esptool.py v2.0-beta2
Connecting....
Detecting chip type... ESP8266
Uploading stub...
Running stub...
Stub running...
Attaching SPI flash...
Configuring flash size...
Auto-detected Flash size: 512KB
Flash params set to 0x0000
Compressed 395836 bytes to 267867...
Wrote 395836 bytes (267867 compressed) at 0x00000000 in 23.5 seconds (effective 134.7 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting...

Build 20150212 firmware can be found in pre_build/latest/nodemcu_latest.bin

A regular console at 9600 baud is used to communicate with NodeMcu. The same connection scheme as per the AT console (above) is used.

picocom -b 9600 /dev/ttyUSB0
NodeMCU 0.9.5 build 20150127  powered by Lua 5.1.4
lua: cannot open init.lua
> gpio.mode(3, gpio.OUTPUT)
> gpio.write(3, gpio.HIGH)
> gpio.write(3, gpio.LOW)

In the above we set GPIO0 to an output, set it high, then set it low.

Although the ESP-01 only has 2 GPIOs, NodeMcu has I2C support and a circuit such as this can extend its capabilities.

Tasmota is firmware providing support for various devices attached to an ESP8266. It has both and HTTP (web) and MQTT interface.

It was primarily designed for SONOFF power switches but can be used with any device to give an MQTT enabled WIFI temperature monitor, for example.

Here is an example seession for a SONOFF basic switch.

Backup factory firmware.

esptool.py --port /dev/ttyUSB0 read_flash 0x00000 0x100000 image1M.bin

Write tasmota firmware.

esptool.py --port /dev/ttyUSB0 write_flash -fs detect -fm dout 0x0 sonoff-basic.bin

Now an example session with the D1 Mini Lite.

Read MAC address.

esptool.py -p /dev/ttyUSB0 read_mac

esptool.py v2.6-beta1
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... ESP8266
Chip is ESP8285
Features: WiFi, Embedded Flash
MAC: xx:xx:xx:xx:xx:xx
Uploading stub...
Running stub...
Stub running...
MAC: xx:xx:xx:xx:xx:xx
Hard resetting via RTS pin...

Backup flash.

esptool.py -p /dev/ttyUSB0 -b 115200 read_flash 0 0x100000 FIRMWARE.BIN

esptool.py v2.6-beta1
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... ESP8266
Chip is ESP8285
Features: WiFi, Embedded Flash
MAC: xx:xx:xx:xx:xx:xx
Uploading stub...
Running stub...
Stub running...
1048576 (100 %)
1048576 (100 %)
Read 1048576 bytes at 0x0 in 92.8 seconds (90.4 kbit/s)...
Hard resetting via RTS pin...

Erase flash.

esptool.py --port /dev/ttyUSB0 erase_flash

esptool.py v2.6-beta1
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... ESP8266
Chip is ESP8285
Features: WiFi, Embedded Flash
MAC: xx:xx:xx:xx:xx:xx
Uploading stub...
Running stub...
Stub running...
Erasing flash (this may take a while)...
Chip erase completed successfully in 4.1s
Hard resetting via RTS pin...

Write tasmota firmware.

esptool.py --port /dev/ttyUSB0 write_flash -fs detect -fm dout 0x0 sonoff.bin

esptool.py v2.6-beta1
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... ESP8266
Chip is ESP8285
Features: WiFi, Embedded Flash
MAC: 60:01:94:b1:1b:ea
Uploading stub...
Running stub...
Stub running...
Configuring flash size...
Auto-detected Flash size: 1MB
Compressed 501424 bytes to 343631...
Wrote 501424 bytes (343631 compressed) at 0x00000000 in 30.3 seconds (effective 132.5 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting via RTS pin...

wget "https://ota.tasmota.com/tasmota/release/tasmota.bin.gz"
gunzip tasmota.bin.gz

esptool.py --port /dev/ttyUSB0 write_flash -fs detect -fm dout 0x0 tasmota.bin
esptool.py v4.6.2
Serial port /dev/ttyUSB0
Connecting....
Detecting chip type... Unsupported detection protocol, switching and trying again...
Connecting....
Detecting chip type... ESP8266
Chip is ESP8285N08
Features: WiFi, Embedded Flash
Crystal is 26MHz
MAC: 60:01:94:b1:1b:ea
Uploading stub...
Running stub...
Stub running...
Configuring flash size...
Auto-detected Flash size: 1MB
Flash will be erased from 0x00000000 to 0x0009efff...
Compressed 649888 bytes to 463643...
Wrote 649888 bytes (463643 compressed) at 0x00000000 in 41.8 seconds (effective 124.4 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting via RTS pin...

After target reboots connect to the tasmota Wifi AP to access the network configuration page.

Enter your SSID and password and the target will reboot.

Once rebooted visit the target device again to perform device setup.

Change the device type, Eg. Generic and save settings. It will reboot.

NodeMcu home page

Tasmota