Simplyduino SPI 32×8 led matrix

I was using LedControl library but I found it horribly slow. It took almost 100 msecs to refresh the display. So I’ve bypassed the library, used my own frame buffer and switched to hardware SPI.The current sketch (you see in the movie) makes use of the buffer shift to update all four displays at once, instead of shifting every row/display separately I’m now pushing screens so fast I needed to introduce a delay(25) between the screen updates (The screen scrolls 1 pixel every redraw).


Arduino LT8900 / LT8910 library

Without much ado i present you my public 1.0 version of a library for the low cost LT8900 and LT8910 2.4Ghz tranceiver module for Arduino and Simplyduino.

From the readme:

This is driver library for use with the low cost LT8900 and LT8910 2.4Ghz transceiver modules as found on ebay.

This library was written because I could not found one, and the chips are incompatible with the NRF24L01(+) modules, even though they look very similar.

The library currently supports:

  • setting channel
  • selection of 1Mbps, 250Kbps, 125Kbps and 62Kbps on lt8910 chips.
  • setting syncword
  • setting lt8900 clock speed
  • settings power and gain
  • sending/receiving dynamic sized packets
  • does not use interrupts
  • hardware SPI

Free binary conversion utility for OS X

Did you ever wanted to quickly analyse the binary value of 0x43? There’s an App for that right on your mac.

Either use the menu or press CMD+3 to switch the calculator from Basic to Programmer and a new box of tools opens up. There’s tools for ASCII, shifting, byte flipping (MSB->LSB!!!) and boolean operators. Very nice indeed!




Happy binarying! (can you even use that as a verb?)

DIY Solder Paste Stencils with a Lasercutter

I recently joined a hackerspace and they have some awesome equipment. One of the machines is a 40W laser cutter. I thought it was time for some experimentation!

For my Simplyduino project I needed a new solder paste stencil because the previous one I ordered at OSH Stencils (these guys offer excellent service!)  is missing a few holes for the components I added with PCB version 1.07. While those 3 extra components are very easy to solder by hand I didn’t want to spend any more more on a stencil. I read quite a few articles on the net on the subject of laser cutting your stencils and here’s my formula.

After a few experimental runs, this is my end result, and I am very happy with it:


There are a little burning marks on the stencil, that’s all!

Configure the cream layer in eagle


Export as DXF

First go to layer settings and disable all but the tCream layer. Then go to file > export > DXF..



The important setting is ‘Fill Area’ which automatically forces the ‘Use line widths’.


Opening the file in VisiCut

Our lasercutter uses VisiCut as a printer software and I figure out that tool allows me to open .DXF files directly without the fuzz of converting it to PDF or SVG first. Another advantage is that the dimensions of the pcb are not lost, saving me a lot of time aligning the stencil.


After positioning, go to Mapping en select ‘Engrave All‘. Edit the details of the mapping and change the resolution to 1200 DPI.  Finally, go to Laser Settings and select power 30 and speed 100. These settings work perfectly for me. I used 125micron Mylar sheets available from


Commercial (zooming in on the 8 pins of a ATMega328p-au)


My results


With some minor tweaking thing may get even better.


Check the photo below for solder paste applied to the board with the above DIY stencil. I shot the photo at an angle so you can see the height of the paste applied.  This close up I notice a tiny alignment shift which is entirely my fault, not the stencil!


After assembly, this looks like this:

IMG_1364(I needed a little rework on the ATMega pins near C2, that kind of messed up the shot )




How to monitor your Synology NAS Health DIY-Style

While working on my Sensorium monitoring website for the Sensoduino, it occurred to me that i can monitor much more than just the plant moisture level. Why not (ab)use the system for monitoring the server health?