I added WiFi to my coffee machine, and I control it with my home automation server, this part is about how I attached the esp8266 module to it.

In part 1 I talked about the idea and how I was planning to do it.

In this part I will describe how I attached the esp8266 WiFi module to my coffee machine.

Hardware

Schematic

 

Buttons

As you can see, in this schematic there are only four buttons connected, instead of 7. This is because the esp8266 module requires GPIO0, GPIO2 and GPIO15 to be connected either to VCC or GND in order to work. This sucked as I already soldered everything when I realized that. I decided to keep the following four buttons:

• Power (top right)
• Small coffee (top left)
• Large coffee (middle left)
• Coffee Strength (middle right)

Power module

In the schematics, I put a regular AMS1117 component to convert the 5V from the coffee machine to 3.3V required by the esp8266, but in fact I use a small module that includes caps and a status LED. The module uses an AMS1117.

Soldering and installation

Board

Most of the components I will be using (from left to right) :

• Power module (5V > 3.3V)
• esp8266 chip (esp-12) and breakout board
• prototype board
• 9x 2n2222a transistors
• 9x 1k resistors

Missing components on the picture:

• 2x 10K resistors
• 11 lines ribbon cable
• ribbon cable connector
• reset button and it’s resistor

You’ll notice that there’s too many transistors on the picture, it should be 4 but there’s 9:

• I originally thought about using a transistor for detecting the LED state on the input pin of the esp8266 but realized a resistor was enough
• there are 7 transistors, one for each button, but I only used 4 at the end. The 7 are soldered though.

Wiring up buttons, power and LED lines

 

On the front panel, I soldered thin wire on one pad of each button (GND is on the bottom pads) then some more wires to the LEDs and power (not visible on the picture), then I routed all these wires on the top left of the PCB. I finally glued the ribbon cable on the top left of the PCB and made the connections.

Now that everything is wired, it is time to start testing the connections and start coding!

Software

Testing connections and functionality

If you hold the top left button and the bottom right button and plug-in the coffee machine, you get into it’s debug menu – this is very useful as it allows me to not only test each button (see picture, if the button is pressed the N turns to Y) but also the LEDs (as the screen color changes when you press buttons)

Manual testing

I’m first testing the buttons without the esp8266 plugged in its socket, just by shorting the different pins to VCC, to check that the transistors circuit are working properly.

Preparing the esp8266 module

Next step is to flash the NodeMCU firmware on the esp8266, then connect a USB-Serial adapter to the module (the yellow and orange cables on the pictures, you see the serial adapter on the top picture).

Using ESPlorer, I can now start creating LUA scripts to control the esp8266.

First thing is to make sure all pins of the esp8266 are correctly configured as output/inputs and set the outputs to low.

For that I wrote the init.lua script as follows (the init.lua script is executed as soon as the esp8266 module starts):

 

This script simply defines the correct direction for each pin and sets all output to low.

Test buttons

Once the init script is in place, I start testing clicking on the buttons via the serial communication in ESPlorer:

 

Test LEDs

A small script to determine the current color of the screen: function redON() return gpio.read(5) == 1 end function greenON() return gpio.read(0) == 1 end — return screen’s backlight based on the LEDs status. function color() if greenON() and redON() then return “yellow” elseif greenON() then return “green” elseif redON() then return “red” else return “off” end end print(“color: “..color()) it simply returns the current screen color every time it is executed. At this point, everything is in place, I am able to control each button separately from the esp8266 serial interface, and retrieve the machine status. Next step is to create a LUA script that contains a bunch of functions to control the machine and get it’s status back.

Make the machine actually smart

Being a C++ developper, I really like modularity, so let’s put all the functions to control the machine in a script called CoffeeMachine.lua – this module will be be called from another LUA file and we won’t have to think about GPIO or how long a button needs to be pushed:

 

This module can now be accessed from another script, in a very easy to read manner:

 

That’s it for part 2, the next part will be about adding the WIFI connectivity and link the coffee machine to Domoticz. See you in part 3!