Actions
Forum Thread Details
  • State Suggested Answer
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 418 subscribers
  • Views 663 views
  • Users 0 members are here
Related

OLED help

funinalaska

Ok, so again, I didn't pay thorough enough attention to the item I was purchasing when I ordered something from ebay.

I ordered this:

http://www.ebay.com/itm/301129164770?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Thinking it was this:

https://www.adafruit.com/products/326

Both units use the SSD1306 IC driver

But the one from Ada has more connection pins.

I am confused because all of the examples and instructables I can find that connect these using I2C use an additional pin for reset.

This unit does not have the reset pin only VCC, GND, SCL and SDA

The other thing is in the description it states that the screen is compatible with 3-5V

Should I assume that it is ready for 5v for VCC as well as signal or should I plan on using a logic level converter?

I bought this as a simple and cheap solution to a small display for network of temperature sensors that are going around an RV.

I am not looking to be able to display graphics only text. I would like to be able to get 3-4 lines of text on this little screen if I can.

It's funny how what you think will be the simple solution never really is.

  • 0

    you don't say what your going to connect this to but from what I can see there should be no problems with not having the reset pin available, it should be performing a power on reset anyway

     

    the supply should not be more than 3.3V, if your only supply is 5V then I would suggest firstly a LDO 3.3V regulator or two diodes in series to drop the volts for you.

     

    if your micro-controller is outputting logic levels at 5V then i would place series resistors of about 2K in the data and clock lines to limit the voltage to the display, this along with its own internal protection should work well enough. If you don't feel comfortable with that then by all means use a logic level shifter

     

    of course if your controller is running at 3.3v anyway then you can simply connect it directly.

  • 0 in reply to Robert Peter Oakes

    Yes, I realized now I did not way what I was connecting it too.

    I am using an Arduino.

    I would like to develop the project using my Uno but then when I am pleased with it I would like to be able to make it permanent on a 5v pro mini

    The other things I am connecting (mostly temp sensors) are all both 5v and 3.3v compliant.

    This project is for an RV and will plan to have indoor and outdoor temperature sensors as well as a temperature sensor in the generator compartment and the engine compartment.

    SO using a pair of diodes between the 5v source on the Pro Mini and a 2kR resistor on each of the data lines should protect it and allow adequate communication?

    I have not done any testing whatsoever yet with the display as I did not want to risk frying it.

  • 0 in reply to funinalaska

    I'd recommend either using a level shifter or switching to a 3.3v pro mini; you really can't assume that the data lines are 5v tolerant on these cheaper displays.  Some of the OLED displays I've picked up on EBay are 5v tolerant, but most are not, and you can't really trust that the seller has any clue regarding voltage requirements.  A 74LVC245 IC costs about 60 cents (USD) from Mouser, which is a lot cheaper than the display (this seems to be Adafruit's go-to solution for level shifting, it's cheap and reliable).  You may also discover that the device is extremely flaky without pull-up resistors on SDA and SCL, especially if you have long leads (over an inch or so) between MCU and display.