Wednesday, 22 July 2015

My adventure with ESP8266 (2/2): flash it!

The first part is here and it is about:
  • hardware
  • software
  • firmwares
  • nodemcu
It contains important information to understand this part.

This table show how to connect the hardware together:

Pay attention to GPIO0, you need it connected only for flashing.

It's time to flash the device with a new firmware using esptool.
I decided to flash a nodemcu firmware.
Connect the GPIO0 to GND and than power on the device.
On my installation on OSX I did this command to flash the device:

python -p /dev/tty.usbserial write_flash 0x00000 nodemcu_21072015.bin

If everything is ok, you should see this message:

Power off the esp8266 than remove the GPIO0 connection and than power on the chip again.

Talk with ESP8266
Now, it's time to talk with the chip.
I use kermit with this .kermrc configuration:

set carrier-watch off
set line /dev/tty.usbserial
set speed 9600

than you can press "c" to connect and typing print ("hello"); you should see the device responding hello back.
Now you can test some commands.

If you have downloaded the luatool, you can write your programs in a text file with lua extension and upload on the board with

python --port /dev/tty.usbserial --src main.lua --dest main.lua --baud 9600

Lua files
Now, you can connect to the esp8266 and type dofile("main.lua"); to run the program.

If the file you are loading on the device, it is called init.lua the esp8266 at every boot will load it: pay attention, a bad init script can block the device forever... The only solution in this case is a re-flash of the device.

If you have any question, feel free to ask in the comments section.
If you like the article please share it! :)

my wirings :)

Tuesday, 21 July 2015

My adventure with ESP8266 (1/2)

This article will explain all the steps I did to succesfully use the ESP8266 chip.
The ESP8266 is a an incredible low cost chip (< 5$!) to enable wifi communication for your project.
It is capable of:
  • create a wifi network: a wifi hotspot
  • connect to existing wifi hotspot
  • programmable digital pins: with I2C or SPI support!
I think this is ideal for many IOT project, at least in a prototype stage.
The chip is pretty new but thanks to its "open" nature and its cost, there are already some alternative firmware available.
This guide is tested for OSX Yosemite, but you can find similar tools also for Linux and Windows.
You can find different variants of ESP8266, but I think this tutorial will work equally with all the versions.

My version is the "04":
isn't it too cute ??? :D

My Hardware
  • CH340G USB to Serial (TTL) converter
  • ESP8266: I have the version 04
  • A stable 3.3v power with enough ampere to power the chip: I used a step down converter from 5V to 3.3V, the LM2596 calibrated with a multimeter and connected to a 5V/2A phone charger
  • a computer
  • driver for CH340G here
  • kermit-c or any serial terminal software (minicom for example). For OSX
  • a firmware to flash: read below
  • here
  • luatool here: valid only with nodemcu firwmare
The default firmware of the chip can be outdated.
This firmware exchange data with AT command on serial line.
A list of commands is here, but commands can change in every firmware.
This firmware is good if you need to connect the ESP8266 to other components (for example an arduino).
My esp8266 comes with a firmware not capable of talk with AT commands in any f*****g way, it started as an hotspot (see image) but I was not able to talk with at any serial speed.

BTW, the hotspot check is a good way to control if the ESP8266 is correctly connected

I flashed a new updated version of the official firmware.
The default firmware is splitted in 4 .bin files: I have to power off and than power on the chip after each flash.
I than tested the AT command with kermit-c, pressing CTRL+J in the terminal after every typed command.
As far as I know, It is possible to create custom programs using the EspressIf SDK and C++.

I decided to test another firmware and the choice was the nodemcu firmware.
This firmware lets you write scripts in LUA language; it's a new language for me, but the syntax is pretty simple.
The advantage here are:
  • upload scripts, without reflashing the firmware
  • the availability of a powerful and simple API with a good documentation

[the second part is available here]