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

January 18, 2011

FlashDevelop IDE under Linux

POC screenshot of FD running on my Ubuntu. The Flash Player i... on TwitpicJust a quick post to note that apparantly you can now run the Flash development IDE FlashDevelop under Linux via Wine with minimal issues. This is great because IMO it’s the best free environment for writing Flash apps, and until now, it was really only usable on Windows.

Forum post with more details

Filed under: Flash,Software — davr @ 8:15 am

July 8, 2010

Reverse Engineering Obfuscated Javascript

I keep getting these spam emails which are making it past Gmail’s spam filter. Basically, it looks like a ‘delivery failed’ notification, with an HTML attachment which you are supposed to think is the original email. So you click on the attachment and open it, to find out which email you sent failed to go through. I finally got curious enough to see what exactly was going on. Here’s how the email looks like in Gmail:

Spam email screenshot

Here’s the actual full contents of the email (some ip / email addresses removed to protect the innocent)

Filed under: Software — davr @ 9:22 am

July 7, 2010

Inexpensive PCB manufacturing for hobbyists

I just found this service which provides very inexpensive PCB’s for hobbyists. His pricing structure is very simple: $5 per sq inch, you get three copies of the PCB, and there’s no setup fees and free shipping. He’s doing kind of a BatchPCB thing, but somehow has made the cost less expensive. (BatchPCB is $2.5 per sq inch, you get one copy of the PCB, and there’s a $10 setup/shipping fee). I haven’t tried it yet, but he says he needs more people to use his service, otherwise he loses lots of money, so I think I’ll give it a go.

Oh, and did I mention, it’s with 6 mil minimum trace/spacing?

Filed under: Hardware — davr @ 4:25 pm

May 30, 2010

Nintendo Wii only $160!

At Amazon. Free shipping & no sales tax for most people, it’s a pretty good deal. Back when I bought mine in Jan 08, they would routinely sell out within 15 minutes of getting more stock on Amazon. I guess now that most everyone in the universe has one, the price is getting reduced

Excellent games I’ve played and can recommend: Super Mario Galaxy 1 or 2, Mario Kart Wii, Rock Band 2, and Dokapon Kingdom

Filed under: Uncategorized — davr @ 8:12 am

April 18, 2010

“The selected volume is offline”

Got this error message when trying to delete a partition / volume in Windows 7 Disk Management. Zero hits on google for the error message, so in case anyone ever gets this again, what I had to do was first assign a drive letter to the partition. For some strange reason, on a dynamic disk, windows wont let you delete a volume if it doesn’t have a drive letter.

Filed under: Uncategorized — davr @ 3:49 pm

March 16, 2010

Comparison of PC-based logic analyzers

Here’s a comparison chart I’ve been working on that compares various PC-based logic analyzers. I made this mostly for myself because I’ve been wanting to buy a logic analyzer, but most of them are very expensive for a hobbyist’s budget. PC-based ones are a good compromise…they can be cheaper than standalone units since they don’t need all the processing and display hardware. I’m currently leaning towards the $120 Zeroplus unit, it seems to provide the best bang/buck. There is the $50 open source one, but I think I’d wait a bit for more reviews of it, to see how good it really works.

View Chart Full-Screen

I’ll write a review when I do decide on one. Also I know someone designing his own Logic Analyzer, if/when he finishes, I’ll give a link to that too.


Filed under: FPGA,Hardware — davr @ 8:50 pm

May 18, 2009

Comparison of Entry-Level (aka cheap) FPGA boards

A while ago I decided I wanted to play around with a FPGA – Field-Programmable Gate Array, basically it lets you design new hardware ICs (Integrated Circuits), without needing a multi-billion dollar chip fabrication plant. So I set out to research the available pre-made development kits I could play around with. They’re quite a bit more expensive to get into than microcontrollers (where you can buy a $3 chip and build a programming cable out of some old scraps of wire), so I looked for the least expensive boards that still had a decent set of features.

I ended up making a comparison chart of FPGA development kits, like I said this was over a year ago, so it may be a bit out of date, but the low-end of FPGA’s doesn’t move all that fast. Most of the information is still valid, but you might be best to do some research yourself before you take the plunge. I only considered boards that featured FPGAs from Xilinx and Altera, since I found other vendors are not competitive in the low-cost arena (low-cost was the most important feature to me at the time, I didn’t want to spend $5000 just to play around. And yes, there are $5000 development boards).

View Chart Full-Screen

If you’re curious, I ended up getting the DE2 (with the educational discount). It costs a bit more, but it has significantly more features, such that I’ll probably never run out of stuff to play with.

The ones highlighted in green are the ones I feel provide the best value, and just coincidentally fall at the $50, $100, and $150 price points.

Filed under: FPGA,Hardware — davr @ 3:26 pm

March 18, 2009

True AdBlock for Chrome browser

I’ve just discovered a true adblock plugin for Google’s Chrome web browser. What these guys have done, is taken the Chrome sourcecode (aka Chromium), stripped out Google’s tracking features, and added in a clone of AdBlock Plus. There’s no fancy UI for it yet, but it supports real regex ad-blocking, unlike those other hacks that either require you setting your hosts file with a million lines, or some annoying proxy you have to configure, or a silly bookmark you have to click on every page.

Check it out here: SRWare’s Iron. As mentioned in the news, make sure to download adblock.ini and place it into the program directory after downloading.

Enjoy the power of Chrome, with the convenience of adblock!

Filed under: Software — davr @ 7:52 am

September 3, 2008

HDR-like photo fun

I’ve been playing around with making HDR photos from only hand-held shots. Mainly because I’m too lazy to always go and get my tripod, set it up, attach the camera, etc etc. It’s a lot easier to just stand there & take a few shots at different exposures while holding the camera as steady as possible.

In the past, all the HDR processing tools required that your images were taken on a tripod and perfectly aligned, or if they weren’t aligned, it could do some simple corrections, but anything too complex would mess it up.

I’ve tried several applications, including Photomatix Pro, PTGui Pro, and Autopano Pro. I know what you’re thinking, two of those three applications are mainly for automatically stitching panoramas…but it turns out automatically aligning images for panoramas is also very useful for creating HDR images.

My very quick comparison of these HDR / panoramic image apps: Photomatix Pro appears to give the most control over the HDR generation process, and with tweaking, gives the nicest output…HOWEVER it’s not very good at handling images which are not perfectly aligned. Autopano Pro is the best at correctly aligning the images, and for creating panoramas in general, but it sucks at HDR tone mapping, having two sliders with obscure labels, that don’t really make it look very nice.
Finally, there’s PTGui Pro — it’s not the best at aligning, and it’s not the best at the HDR generation, but it’s pretty good at both, so in most cases it gives the best overall results.

Below, you can see an example of a shot I took, that would be impossible without some sort of HDR effect:

Filed under: Photography,Software — davr @ 1:49 pm
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