Jul 21, 2014

New ledRing controller


Some of you may have seen a project I wrote about on instructables. http://www.instructables.com/id/Rainbow-Ring-Wall-Clock/

Well there were a few problems I faced with it:
  • Underpowered micro-controller
  • Incorrect mixing of resin
  • Broken led after resin had set 
 (I do intend to do a failure analysis on that LED at some point. When I get the time)

So it was definitely time to do a second revision.




After a few solid hours in altium I came up with this:

 The controller is still a TI MSP430 part. This time the pinnacle (as of jul-2014) of the value line series. MSP430G2955.

Some notable features:
  • 56kb FLASH
  • upto 16MHz CPU speed.
  • 4kb RAM
  • Comes in a slim 40 pin 6x6mm QFN package.
  • Upto 32 capacitive touch sensor pins.
After ordering the board for my usual supplier, elecrow's 5x10cm PCB service. I got to sit around for around 2 weeks until I had the board in my hands.





Before soldering up a board to test and ensure everything was working as it should I had to write some code. The last version of the clock was compiled with the opensource msp430gcc which although very stable is no longer maintained, and sometimes difficult to get installed.

I opted to run with the new and shiny RedHat/TI driven msp430gcc-elf compiler set. After downloading TI's CCS from their website you are given the option to install this open source compiler. Although it is still in beta it offers no code-size restrictions unlike the MSP430's other compilers.

The board soldered up beautifully, unfortunately there were a few small flaws. As always.
  • I designed the board to take 0603 components, but only had 0402 on hand.
  • Footprint for the level shift is too big, as seen on the left of the photo.
  • Footprint of the voltage regulator is too small, not seen in this photo.
Other than those small issues, the board works perfectly.



I plan on selling kits/assembled boards for those who would like. If you cannot wait then you can build your own! This project is open source. All the files are available for download.

Here are the PCB board files in Altium format:
http://forum.43oh.com/topic/4920-120-led-ring-clock/page-7#entry48125

I am running another board to correct those small errors, and adding an easier to use debug connector.
During the fabrication time I will be writing code, which will all be released when I make up my first batch of ~5 to sell. Depending how they sell, I will probably make batches of 10 depending on demand. The interest check is located here on tindie.
https://www.tindie.com/products/Greeeg/ledring-clock/

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