just got a cheap OLED (128x64) screen from eBay but it doesn't seem from a fly-by-night operator, it's got a proper website printed on the product.
the seller description (as well as the website) says 3-5V, but i have checked the datasheet of the SSD1306 driver chip which states logic levels are for 3.3V.
i understand these are probably copies of an Adafruit product which does state level-shifting circuits are added to their boards (picture also included below).
i have a level-shifting board (8-bit) and know that it (the circuit) involves a transistor (MOSFET) and two resistors that pull-up to the respective voltages on either side.
you can see the Adafruit board has 3-pin components, so i'm guessing these are the transistors and those are indeed level-shifting circuitry.
however, on the product i got, i only see resistors and capacitors, and one diode. (there is a voltage regulator, so that seemed to be a hint that there was some possible level-shifting.)
i guess i should "grow up" and try to trace out the circuit myself (!!) and see what it looks like, but without any schematic (didn't notice one on the adafruit product page either) i thought i'd first broach the issue here and get some feedback, maybe some tips.
The product i got;
The adafruit version for comparison; (different shape because i copied the 128x32 version) P.S. also just noticed the 6-pins, so i might have even clicked the SPI version (sorry!) - anyway, it was just to compare the level-shifting circuitry.