These are my notes for flashing and programming the LoLin V3 ESP8266 ESP-12E CH340G WIFI Network Development Board. This may work on other ESP8266 based boards as well. This is for Linux only and specifically on Ubuntu 18.04 x84-64. I suspect it will work on other Linux distributions.

I bought 5 on ebay with shipping they were about $3.59 US each. They come from China at that price, so you are going to wait a few weeks to reach the US. Search EBay for "NodeMcu Lua ESP8266 ESP-12E" The LoLin ones I bought came with 4 MB flash. This particular board is too wide for a standard breadboard, but you can attach 2 mini breadboards together.

You want to make sure Ubuntu discovers your device. I just plugged it in without any additional drivers and it showed up. I used a standard micro USB cable to connect to PC.

• lsusb
• Bus 006 Device 002: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
• Device should show up as serial port /dev/ttyUSB0 if something doesn't already occupy that port.

This will bring your device up to the latest NodeMCU release. I used the dev branch with floating point. I had to use master branch to get u8g module working, so build to suite your needs.

• Use NodeMCU custom builds to create a NodeMCU image.
  • I selected dev branch and used pre-selected defaults.
• Make sure you can do serial communications without root access
  • sudo usermod -a -G dialout username (Use a non-root username)
  • You will have to log out or reboot for this to take effect.
• Install esptool.py
  • sudo -H pip install esptool
• Verify esptool can communicate with device.
  • esptool.py chip_id

  Connecting....
  Detecting chip type... ESP8266
  Chip is ESP8266EX
  Features: WiFi
  Uploading stub...
  Running stub...
  Stub running...
  Chip ID: 0x00000000
  Hard resetting via RTS pin...

• Check flash size.
  • esptool.py flash_id
  • Detected flash size: 4MB
• Blow away flash.
  • esptool.py erase_flash
• Flash image with file you downloaded. Replace file name at end of command.
  • esptool.py write_flash --flash_mode dio 0x00000 nodemcu-dev-7-modules-2018-03-10-17-09-58-float.bin

I had an instance where my code was supposed to put the NodeMCU in deep sleep, but crashed instead. Since I used a init.lua I was unable to flash, erase flash, etc. A lot of the solutions you'll find out there do not work. The only thing that worked for me was to:

• Run wire from RST to GND
• Plug in NodeMCU to computer
• Remove wire from GND
• Flash or erase as normal

I'm using ESPlorer, but Arduino IDE could probably be used as well.

• Install Java 8 JDK if you do not have Java installed.
• Download latest ESPlorer.zip
• Extract to ~/
• Run ESPlorer
  • cd ~/ESPlorer
  • java -jar "ESPlorer.jar"
  • NodeMCU dev branch uses 115200 baud, not 9600. It should auto detect the port.
  • Click on Open, click RTS twice and device should auto detect

  
     Communication with MCU..Got answer! Communication with MCU established.
     AutoDetect firmware...
  
     Can't autodetect firmware, because proper answer not received (may be unknown firmware). 
     Please, reset module or continue.
  
     NodeMCU custom build by frightanic.com
         branch: dev
         commit: 5c8af3c452574448d471e271231b36ac3fff6b1b
         SSL: false
         modules: file,gpio,net,node,tmr,uart,wifi
      build 	built on: 2018-03-10 17:08
      powered by Lua 5.1.4 on SDK 2.1.0(116b762)
     lua: cannot open init.lua
     > 
  

Let's try a simple function to list WIFI APs.

• Copy code to the editor on the left side of ESPlorer.

function listap(t) -- (SSID : Authmode, RSSI, BSSID, Channel)
    print("\n"..string.format("%32s","SSID").."\tBSSID\t\t\t\t  RSSI\t\tAUTHMODE\tCHANNEL")
    for ssid,v in pairs(t) do
        local authmode, rssi, bssid, channel = string.match(v, "([^,]+),([^,]+),([^,]+),([^,]+)")
        print(string.format("%32s",ssid).."\t"..bssid.."\t  "..rssi.."\t\t"..authmode.."\t\t\t"..channel)
    end
end

• Select all the code in the editor.
• Click Block button and code should upload to ESP.
• Clear editor and paste wifi.sta.getap(listap)
• Put cursor on line and click Line button

> wifi.sta.getap(listap)
> 
                            SSID	BSSID				  RSSI		AUTHMODE	CHANNEL
                            test	e7:98:f1:45:36:b8	  -47		3			3
                        SXE465TF	21:e7:1a:88:9b:c5	  -65		3			11
                            xyz1	49:e1:1c:52:65:c6	  -64		4			11

This uses a init.lua and blink.lua script to flash an LED on boot. Change pin number in blink.lua as needed. Just create files in ESPlorer (blink.lua first) and click on Run. init.lua sets up wifi to use a static address and runs blink.lua.