Easily connect an SSD1306 OLED display (or two) to ESPEasy

Let's see, step by step, how to adding a display to your project with NodeMCU or Wemos D1 Mini and ESP Easy.

In this case, I will take the example of the CO2 meterbut it can be done with any other type of project.

One of the advantages of ESP Easy (and my favouriteis that it enables us to connect to our project many different accessories without having to program or complicate our lives. with firmware modifications or adaptations. One of the most interesting elements are the displays, or "screens".displays".

And it's not just that it allows us to connect very easily "a screen"is that they are many different screens that we can connect almost effortlessly.

In this case I have decided to add a SSD1306 type display to the CO2 meter. OLED monochrome (blue characters on black background) of 0.96 inches (0.96″).

I have opted for this display because of these two advantages, but they are not the only ones:

• Use only two cables data (plus the two power supply pins). This makes it extremely easy to connect and, by using only two pins, leaves plenty of free pins for connecting other sensors and accessories.
• OLED technology has very low consumption. Important for those who want to use the display in a portable project with batteries.
• Looks pretty good outdoors. This is very important on certain occasions.
• Low price. These screens can be obtained for around €3 with shipping from China or around €7 from Spain.

Connecting the SSD1306 display to the NodeMCU

The connection couldn't be easier. You have to make four connections. Two for power and two for data.

All you have to do is connect:

• VDD from SSD1306 to Vin of NodeMCU
• GND from SSD1306 to GND of NodeMCU
• SCL from SSD1306 to D1 of NodeMCU
• SDA from SSD1306 to D2 of NodeMCU

If your NodeMCU board has a VU pin, connect VDD to that pin. instead of Vin. Not all NodeMCU boards have this pin.

IMPORTANTDon't rely on the order of the connections and double check them on your board. Sometimes different manufacturers make such changes that can make your day if you are not careful.

IMPORTANTThese instructions are for screens operating with 5V power supply. Make sure your display is powered at 5V. If your display is powered at 3.3V you will need to connect the VDD pin of the display to one of the pins marked 3.3V on your NodeMCU or Wemos D1 Mini (on some boards the silkscreen on this pin may be "3V" or "3V3").

The connection to another board, different from the NodeMCU based on ESP8266, or another one based on ESP32, will be very similar. We will only have to pay attention to the change in the pins. Here is the connection diagram with the Wemos D1 Mini, for example:

Configuration

The configuration is also very simple.

You have to follow the steps below (click on each image to see it bigger):

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Displaying text on the display SSD1306

The SSD1306 allows you to display, in the configuration you have seen above, eight lines of text.

These eight lines of text may contain the following types of data:

• A fixed text
• The value of a sensor
• An ESP Easy variable such as the current time or your IP address.

Showing fixed text

As you have seen in the previous point, you have eight lines of text in which you can display either fixed text (in the example above, line 1 shows the fixed text "CO2 METER" with two spaces in front of it so that it appears centred on the screen).

To display fixed text, simply type the text you want to display on the corresponding line.

You can add uppercase, lowercase and some special characters by adding certain codes (note that it is not possible to write accented vowels):

Name	Character	Code
Grados	˚	{D}
Degrees Celsius	˚C	degreeC degree_C
French inverted commas	" "	{<<} {>>}
Greek letter Micro	µ	{u}
Currency	€ ¥ £ ¢	{E} {Y} {P} {c}
Mathematical symbols	x¹ x² x³ ¼ ½ ¾ ± × ÷	{^1} {^2} {^3} {1_4} {1_2} {3_4} {+-} {x} {..}

Showing the value of devices

To display the value of a device (a temperature, humidity, CO2 or any other sensor) you only have to include the device name and the value you want to be displayed in the format [DEVICE#VALOR].

In the example I have shown the PPM value of the CO2 device.

If you look at the configuration of that device (from the Devices tab and selecting the device you want to see):

You can see that the name of the device is "CO2"and the value we want to display on the screen is "PPM"Therefore, we will have to put in the line where we want to show it [CO2#PPM].

Note that you have a column for indicating the number of decimals that you want to be displayed. If the value must be an integer without decimals you can set it to 0.

Displaying system variables

There are a number of variables updated by ESP Easy itself that you can display.

These variables are as follows:

• %sysname% - Replaced by the name of the ESP Easy unit (defined on the Config tab).
• %ip% - Replaced by the ESP Easy IP
• %systime% - Replaced by current time

Combining the three

You can combine fixed text, sensor values and ESP Easy variables on the same line, allowing you for example to put in one line "CO2: [CO2#PPM] ppm" so that you can include a title before the sensor value and the units after it.

You could also type "TIME: %systime%" or "IP: %ip%".

NTP configuration in ESP Easy, or "setting the ESP8266 to time".

If you want to display the current time on the screen, using %systime%", or need it for some other reason, you have to take into account that the ESP8266 has no internal clock so you need to check the internet time.

It does this by means of the NTP protocol (Network Time Protocol), which is a very commonly used system in computers (your computer probably uses it, even if you don't know it, as is the case with Windows and Mac OS) and ESP Easy is prepared to use it very easily.

To set it up, you will have to follow a series of steps:

1. Go to the "Tools" tab.
2. Select the "Advanced Settings" option.
3. Activate the use of the NTP protocol and assign europe.pool.ntp.org (or the one you prefer) as time server.
4. Activate the DST option so that ESP Easy automatically switches between summer and winter time.
5. Enter the corresponding time difference. In Spain 60 minutes, except for the Canary Islands, where it is 0.

Step-by-step video instructions

Although the process is simple, and should not give anyone too much trouble, I have recorded a video with step-by-step instructions on how to add the screen.

Even more options "Display - OLED SSD1306/SH1106 Framed"

If you want to, you can still more viewing optionsI recommend that when selecting the display in the ESP Easy drop-down menu you try the "Display - OLED SSD1306/SH1106 Framed"(instead of the "Display - OLED SSD1306"(see above).

Please note that "Display - OLED SSD1306/SH1106 Framed"consumes some more memory ESP8266 that the "Display - OLED SSD1306"so that in devices with many sensors connected o many rules extensive, it could lead to memory problems (normally it should not cause any problems).

I used it to write the article CO2 Sensors MH-Z19B FALSE and in the accompanying video, with two MH-Z19B sensors connected (one original and one fake), the SSD1306 display and three WS2812B LEDs without any problems, and there is still free memory for more.

The set-up is pretty much the same. This is how I have it set up:

And so the content (in this case I tell it to hide the header (where the SSID of the wifi network could be displayed, among other data), I tell it to scroll if there is a line that is too long, to turn on the display when new text arrives - in case it has been turned off by some rule -, and Line 1 and Line 2 I tell it to show me the data of the two sensors I have connected.

Write to the "Display - OLED SSD1306/SH1106 Framed"by means of rules:

In the above example the display is updated every 60 seconds, so any text or value displayed will only be updated every 60 seconds.

If you want you can write directly on the screen from the rules via the command oledframedcmd,,. (the command has to be a single parameter so if it includes spaces or commas you will have to write it in brackets, as in the following example), which gives you much more control.

In the following example rule, the value CO2#PPM is updated instantly on the display each time it changes. In addition, if CO2#PPM is less than 400, it displays the message "Initialising...", instead of its value.

On CO2#PPM do
  If [CO2#PPM] > 399
    oledframedcmd,1,"[CO2#PPM] ppm"
  Else
    oledframedcmd,1, "Initializing..."
  Endif
Endon

Of course, you can combine it in the rules as you like. For example, in the following example I use an ESP Easy timer to update in the same rule the value shown on the display and the colour of a flashing "traffic light" LED depending on the CO2 level.

On Rules#Timer=1 do
  if [CM1106#PPM]>1500
    NeoPixelAll,32,0,0,0 // LED red
    oledframedcmd,1,"[CM1106#PPM] ppm"
  Elseif [CM1106#PPM] > 1000
    NeoPixelAll,16,9,0 // LED orange
    oledframedcmd,1,"[CM1106#PPM] ppm"
  Elseif [CM1106#PPM] > 399
    NeoPixelAll,0,32,0 // LED green
    oledframedcmd,1,"[CM1106#PPM] ppm"
  Else
    NeoPixelAll,0,0,0,0 // LED off
    oledframedcmd,1, "Initializing..."
  Endif
  looptimerset_ms,2,100
Endon

On Rules#Timer=2 do
  NeoPixelAll,0,0,0,0 // LEDS OFF
  looptimerset_ms,2,0
  timerSet,1,2
endon


On System#Boot do
  NeoPixelAll,0,0,0,0 // LEDS OFF
  timerSet,1,2
EndOn

The size of the texts on the screen

The display will automatically adjust the size of the texts. to the number of lines you configure. Just select the number of lines you want to display, in the "Lines per Frame" option.

If you put more lines than the screen is capable of displaying, it will display the different lines in different screens that will pass by one after the other (you can change the time between screen jumps).

You can also make the screens scroll by at the push of a button and even change the display of the screen shown from the rules.

As you can see, the display options are many and, as always, no programming required. Just make the changes you want from one convenient web page.

Connecting two OLED displays

In some projects it can be interesting to connect two OLED displays (or more than two) simultaneously.

There is no problem to do so and is very easy.

Here you can see a prototype CO2 meter with two 1.3″ OLED displaysThe two displays, one shows the CO2 concentration permanently and the other can display different data, such as temperature, humidity, etc.

As we have seen above, the OLED display has an I2C address that the ESP8266, ESP32 or other microcontroller uses to communicate with it. What we need to connect two displays to a single microcontroller is each display has its own I2C address and, quite simply, connect them in parallel and use them as if they were two completely independent screens.

Changing the I2C address of the OLED screen

IMPORTANT: It is very important to make sure that you use OLED displays that allow changing the I2C address. (many don't), otherwise you won't be able to do it this way (you would need an I2C multiplexer, which complicates things a bit). Below are the links to the screens I use that allow I2C address change.

For example, this 1.3″ OLED screen (a little larger than the normal ones, which are 0.96″) allows for change the I2C addressbetween 0x78 and 0x7A, relocating a resistor:

You can find this 1.3″ SSD1306 display on AliExpress by clicking here. If you prefer a screen 0.96″ SSD1306 that allows to change the I2C address, I bought this one. Both allow the I2C address to be changed.

Connection of two OLED I2C displays

If you are using a ModeMCU board to connect the two SSD1306 OLED displays in parallel would look like this:

If you are going to connect the SSD1306 OLED displays to a Wemos D1 Mini board the connections would be as follows:

All that remains is to configure ESP Easy to use the two OLED displays.

Configure ESP Easy to use two I2C OLED displays SSD1306

You simply have to add in the configuration (Devices tab) two devices "Display - OLED SSD1306/SH1106 Framed". (exactly as we have seen before with a single screen) and configure each one independently, with the data we want:

In some cases, the I2C addresses may not match what is displayed on the screen. (For example, on this screen I used, the silkscreen says that the addresses are 0x78 and 0x7A but the real addresses are 0x3C and 0x3D.

Remember that you can find out the addresses of the devices connected via I2C with the "I2C Scanner" in the "Tools" tab).