in Applications

Playing With A Mini Led Panel

During one of my trips to China I found some Mini Led Panel in a shop.

They are mini led displays that are able to scroll up to 5 five 250 characters messages. They come with a USB cable and some Windows software that allows you to program them. I actually bought two of them for something like 15 USD. 

I was quite intrigued by the concept of using them to display alerts on my personal computer or show direct messages coming from Twitter.

Unfortunately the application that comes with the device will only run on Windows and it actually does not allow me to use them as i would like.

In the first place I tried to understand how these devices were built. 

I found that they are based on the Prolific PL2303 USB to Serial Bridge controller. This is quite famous for these kind of device. You can find the datasheet here. Luckily enough there is a Mac OS X device driver than you can use to drive this device.

The next step was to reverse engineer the protocol used to program the device. Actually there is no documentation at all coming with the product. Since it is basically a serial device it had not to be that hard to understand the protocol doing some traces. Unfortunately on a Mac there are no free application to trace communication over serial interface/ Actually the Mac does not have any serial interface at all. Moreover the application to program the device only works in Windows.

I have a Windows XP virtual machine running on Parallels on my Mac so I decided to trace the protocol in that environment. From the long past I remember that I used a great utility from Sysinternals, now Microsoft, called portmon.exe. This is  a fantastic small utility that you can use to trace and debug serial communications on a Windows box. That was just what I needed.

After a couple of hours of debugging and a few traces I came out with a good understanding of the protocol. There are still some unknowns that I was not yet able to decode from the protocol (e.g. how to send bitmap images) but that was not critical for the realization of my idea.

The next step was to write a Max OS X application to program the device. I just wanted to write a very simple command line utility that I could user from any shell script on the system. So I did. I started from the Serial Port example in the Apple SDK and wrote some very basic utility implementing the protocol.

Finally I decided to use the mini led panel to display mentions coming from Twitter. I just modified a bash shell script to do just that at 15 minutes intervals. I remember I had seen a very simple shell script on Linux Journal so I used that as a starting point.

So, after four hours of work I had my hardware and application up and running.

I have noticed that a lot of similar devices share the very same protocol so you may use the same code to drive them.

If you wish here is a link to the complete Xcode project where you will find the source code of the command line utility and a copy of the shell script. I am putting these files in the public domain so do whatever you want with them. Download mlpupdate Xcode project here.

Finally, here is a photo of the device working:

mlpupdate

  • http://www.freemicrosoftpointscodes.com/ Free Microsoft Point

    Wow, that is an awesome project. Not if you could get a hold of the manufacturer of the product you could probably make a pretty good profit off of something like that.

  • http://midnightwriter.net Andrea

    That's great!! I agree with the other comment that you could make a good profit off of that!!!

  • http://www.wheyproteinsupplements.com Whey Team

    That's most definitely a fascinating concept. I've got no idea of the ins and outs, but, it's definitely interesting!

  • http://oowwl.com/ anna

    So interesting in enjoying.
    Simplicity that does not make so many difficulties.
    Yep, it is right.
    Thanks for good info.

  • http://techbostonworks.com/ henrie

    Well-well-well-….
    It is good practice for sharing.
    I like it so much for getting it in the future.
    Good job.
    Thanks.

  • http://the-finance-online.info Pamela

    Amazing gadget, I would love such a panel in my room, could you tell me where I can get it from, I mean a webstore.

  • http://www.guidehut.com johnny

    Well done. I Have a similar thing hooked up to my PC but i used an off the self interface board.
    great work on the reverse engineering.

  • http://www.ocgames.com Gamerooms

    Thanks for sharing the Xcode project. I am done taking a look at it and I have to say that you have some talent man.

  • http://www.xamres.com/ xamres

    That's great!! Iam searching for like this projects.Thanks for sharing dude

  • http://www.cheapwirelessinternet.org Mark

    These LED panels are totally cool. Do you know if they make anything like this in the US? Would love to get one for my sons room to fit with the theme we designed the room with. Thanks!

  • http://1stblogger.com/ 1stblogger

    Amaz­ing gad­get, I would love such a panel in my room, could you tell me where I can get it from, I mean a webstore.

    • Alessandro

      I have never been able to find one of these online yet.

      I used to buy a bunch of them each time I was in Shanghai for business trips.

      Maube some chines online gadget store may carry them.

  • day

    Pls email me your Xcode , i am unable to download ,the link dosent have the project code.

    • Alessandro

      The link to the source code is now working. It was my fault when migrating the blog. Have fun!

  • day

    Hi Alessandro
    Thank you very much , i am able to download now

    Thanks again
    Dayal

  • day

    HI Alessan­dro
    the Photo of the working device is not working ,i wiould like to take a look at it

    Thank you again.