The ssd13306 library I’m using for the SSD1331 OLED Screen introduced weird behavior with displaying text on screen. I later found out that the issue was in the inputs to the functions. The function which displays text on the screen asks for a character array, instead of the usual string. Apparently, the function expects the character array to be 1 character longer than the amount of characters needed to write which should contain the null terminator.

As I dug deeper into this ssd1306 library, I realized just how unfinished and unpolished it is compared to something like from Adafruit. Even though I couldn’t get other more popular libraries to work with ESP’s hardware SPI (Like Adafruit SSD1331 library or SSD_13XX library), I’m starting to reconsider and I’m thinking of giving them another chance.

Fig. 19 - The libraries available for the SSD1331 in the Arduino library manager.

Other than that, I was able to capture temperature and humidity values from a DHT11 sensor, send it from one ESP to another and display it on an OLED:

Fig. 20 - DHT11 sensor data from one ESP displayed on a screen on another ESP.