ESP8266 and Air Quality sensor

While exploring the world of connected things (a.k.a. #IoT) the ESP8266 popped up as an new platform for measuring and sensing data - making Things becoming more relevant. SENSable Things are starting to sense our environment, while feeding data to a cloud the question comes up: what should I read out of the values?

Did you know that VOCs (volatile organic compounds) are emitted by bread? Fresh bread smells not only to us - it has a meaning to VOC sensors, fresh bread smell like value 170! Or can you sense  the air in your house - when and how long you should open windows? ...

But let's first dig into the hardware part:

Not going to cover the ESP8266 wiring, there are tons of good tutorials out in the web

Installation of ESP8266 tool chain on Raspberry Pi

Besides the software installation of compiler and tools for flashing the ESP8266 there is also the demand of an appropriate FTDI 3.3V wiring to the ESP8266.

1. ESPtool – python base tool for flashing the ESP8266

wget --no-check-certificate https://github.com/themadinventor/esptool/archive/master.zip

unzip master.zip

cd esptool-master

sudo python setup.py install

2. LUAtool – libs and samples for coding in LUA language

wget --no-check-certificate https://github.com/4refr0nt/luatool/archive/master.zip

unzip master.zip

3. NODEmcu – firmware for the EPS8266 supporting LUA coding

wget --no-check-certificate https://github.com/nodemcu/nodemcu-firmware/archive/master.zip

unzip master.zip

Flash the NODEmcu firmware

Frist make sure the GPIO0 is wired to GND to allow acceptance of new firmware.

Flash the latest firmware to ESP8266:

pi@raspberrypi ~/esp/nodemcu-firmware-master/pre_build/latest $ python /home/pi/esp/esptool-master/esptool.py --port /dev/ttyUSB0 write_flash 0x00000 nodemcu_latest.bin

Connecting...

Erasing flash...

Writing at 0x00062000... (100 %)

Leaving...

Done - Unwire GPIO0 before the next step.

Now we download the auto startup LUA script to allow the ESP8266 connection to an access point:

pi@raspberrypi ~/esp/luatool-master/luatool $ python /home/pi/esp/luatool-master/luatool/luatool.py --port /dev/ttyUSB0 --src init.lua --dest init.lua --verbose

Set timeout None

Set interCharTimeout None

Upload starting

Stage 1. Deleting old file from flash memory

->file.open("init.lua", "w") -> ok

->file.close() -> ok

Stage 2. Creating file in flash memory and write first line->file.remove("init.lua") -> ok

Stage 3. Start writing data to flash memory...->file.open("init.lua", "w+") -> ok

->file.writeline([==[print('init.lua ver 1.2')]==]) -> ok

->file.writeline([==[wifi.setmode(wifi.STATION)]==]) -> ok

->file.writeline([==[print('set mode=STATION (mode='..wifi.getmode()..')')]==]) -> ok

->file.writeline([==[print('MAC: ',wifi.sta.getmac())]==]) -> ok

->file.writeline([==[print('chip: ',node.chipid())]==]) -> ok

->file.writeline([==[print('heap: ',node.heap())]==]) -> ok

->file.writeline([==[-- wifi config start]==]) -> ok

->file.writeline([==[wifi.sta.config("SSID","passkey")]==]) -> ok

->file.writeline([==[-- wifi config end]==]) -> ok

->file.writeline([==[wifi.sta.connect()]==]) -> ok

->file.writeline([==[tmr.alarm(1, 1000, 1, function()]==]) -> ok

->file.writeline([==[if wifi.sta.getip()== nil then]==]) -> ok

->file.writeline([==[print("IP unavaiable, Waiting...")]==]) -> ok

->file.writeline([==[else]==]) -> ok

->file.writeline([==[tmr.stop(1)]==]) -> ok

->file.writeline([==[print("ESP8266 mode is: " .. wifi.getmode())]==]) -> ok

->file.writeline([==[print("The module MAC address is: " .. wifi.ap.getmac())]==]) -> ok

->file.writeline([==[print("Config done, IP is "..wifi.sta.getip())]==]) -> ok

->file.writeline([==[-- dofile ("web.lua")]==]) -> ok

->file.writeline([==[end]==]) -> ok

Stage 4. Flush data and closing file->file.writeline([==[end)]==]) -> ok

->file.flush() -> ok

->file.close() -> ok

--->>> All done <<<---

Now we can monitor the NODEmcu console and see output of the LUA script:

pi@raspberrypi ~ $ screen /dev/ttyUSB0 9600

NodeMCU 0.9.5 build 20150214 powered by Lua 5.1.4

lua: cannot open init.lua

>

As the init.lua has not yet started either do an RESET, POWER ON/OFF, or enter dofile(“init.lua”) to execute the script.

NodeMCU 0.9.5 build 20150214 powered by Lua 5.1.4

init.lua ver 1.2

set mode=STATION (mode=1)

MAC: 18-FE-34-FE-34-0C

chip: 16659468

heap: 17184

> IP unavaiable, Waiting...

IP unavaiable, Waiting...

ESP8266 mode is: 1

The module MAC address is: 1A-FE-34-FE-34-0C

Config done, IP is 192.168.2.115

>

Done – ESP8266 is now connected to the access point showing its DHCP IP address.