Robots w/Lasers

August 19, 2011


Well, not completely DIY, I’m not making the OLEDs from scratch in a chemistry lab. But instead of buying an OLED from sparkfun for $37, or the OLED with a breakout board for $60, I found taobao, essentially a chinese version of ebay. Some seller was selling a very similar display for only ¥20.80 ($3.25). Below is a google-translated screenshot. Automated translation for chinese-to-english still has a way to go unfortunately.

Anyway, you can’t order directly from, they only ship to people living in China. However a whole cottage industry has sprung up around exporting from taobao to USA, there are dozens and dozens of sites with poor english on them, who will buy from taobao, and then re-ship the package to you, for a nice fee of course. I went this route, choosing (after seeing a review saying someone else used them successfully). I ended up paying all told $5 per OLED display.

Now the product page had zero technical info on the displays, and contacting the seller (in Chinese of course), they didn’t have any further information either. However I was able to track down the datasheet for both the display itself and the controller chip, which I’ve uploaded here:

OLED: UG-2828GDEAF02.pdf

Controller chip: SEPS225.pdf

The whole reason I started on this oled ordeal, is after reading this article on driving OLEDs via an AVR microcontroller by rossum. He gets pretty good results out of them, and I wanted to try something similar. I couldn’t find any US source of cheap OLEDs that fit the bill, after scouring ebay and so on. I did find which has a couple cheap oleds, but unfortunately the 1.5″ color display could NOT be driven by SPI, instead requiring a more complicated 8 bit parallel interface, that I didn’t want to have to fool with. SPI is ideal for AVRs since it can output data up to (Clock Speed/2) bits per second, meaning an AVR running at top speed of 20MHz could output at 10Mbit/sec (assuming you do nothing but output data, which means in practice it’s a bit lower). Rossum was able to output pixels fast enough to refresh the entire display at 30fps, which is great (check out the video on his page).

Speaking of rossum, he has some nice little breakout boards using a FAN5331 boost converter to generate the driving voltage for the OLEDs (which generally need 12-15V to drive the display), along with a buffer chip to allow you to interface 5V logic to the 3.3V OLED if you wish. Unfortunately the pinout and such of my OLED is different from his, including different connector size, so I couldn’t use it unchanged. Luckily he provides the source to his boards, so taking those as a starting point I’ve designed my own breakout boards:

Source: pdf, sch, brd (WARNING! These are a work in progress, have not been tested yet. It may short VCC to GND and set your cat on fire!)

I’ve sent away to have them made by laen’s pcb service, they should be back any day now, and I can start putting them together and see what happens! Watch this space for updates.



Filed under: AVR,Hardware — davr @ 4:56 pm

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