Review on 🔹 MakerFocus 6pcs I2C OLED Display Module 0.91 Inch Blue SSD1306 OLED Screen Driver 3.3V~5V for Arduino by Charles Adelaja

Update 1: I'm about to find out why I'm still having problems with this device. After posting, I found that at least for the NodeMCU8266, contrary to my original assessment, pull-up resistors might not be needed. (In fact, the schematic diagram in the image listing shows that they are built in.) I have confirmed that the device can also work with the Arduino Uno, so as described it is both 3v3 and 5v compatible. However, Uno only works when the 4.7 kΩ resistor pulls the SCL line high. Strange. On the other hand, I can't get it to work reliably and I'm not sure if this display module is defective. It's time to pull out the logic analyzer and see what's going on. I'm temporarily changing my rating to 4 stars because a) it can work as expected and b) the supplier was extremely helpful in resolving the issue amicably. They are good, reliable people. (Also they stated that they asked their supplier to insert the headers but to no avail. It's not critical anyway.) *** I give 2.4 stars here. I received two devices - both work. 1) I understand the dissatisfaction with R. Arnold's review. However, the Adafruit library works in the sample code ( ssd1306_128x32_i2c ). However, good I2C knowledge is required. I learned it the hard way. There was an 8266 (3.3V) as the MCU plus an Adafruit temp/humidity sensor and this display on the I2C bus. I knew that I2C needed pull-up resistors on the SDA/SCL, but the sensor has pull-up resistors built in and theoretically you only need one set. The sensor communicated normally and I was able to detect both devices using the I2C scanner code in the Adafruit library examples. No sign of life from the display until I added 2 resistors of 3.3V to SDA and SCL - one each of course. Aha! (I used 4.7 kOhm - YMMV.) Don't understand why the display's I2C address was recognized on the bus, but nothing was displayed without additional resistors. However, including a rough diagram in the package will help speed up debugging, especially for those new to I2C. (By the way, the reset pin listed in the Adafruit library seems to be optional and can be changed in the source code from "4" to "LED_BUILTIN.", at least 8266.) 2) I don't think the text is very good readable without strong readers It's sharp but very very small 3) There are sound economic (seller) and expedient (buyer) reasons not to solder connectors, but would it be too expensive to throw in a pair of 4 pins? 4) No mounting holes!