Thursday, July 17, 2014

New kit in store: simple clock with HDSP-2534 display

Update July 31, 2020: See the latest revision here.

The centerpiece of this clock kit is the vintage-style 8-character display HDSP-2534 originally from HP, currently manufactured by Avago. The assembled clock looks like in the photo below. The dock, not included in the kit, is a miniB USB phone charger; it can be easily sourced from ebay, if you don't already have one. (You can even get a fancy one, e.g. custom-made exotic wood, on

The kit includes the following components:

  • PCB;
  • ATmega328P, with bootloader and fuses for 8MHz internal clock, and the sketch preloaded (also downloadable from here);
  • HDSP-2534 display;
  • 595 shift register;
  • DS1307 real time clock;
  • 32kHz crystal
  • CR1220 battery;
  • battery holder;
  • push buttons (x2);
  • capacitor 100nF (x3);
  • 10k resistor (x3);
  • 28-pin socket;
  • 16-pin socket;
  • 8-pin socket;
  • 6-pin machined female header (x4).

   $40, free shipping to North America

Note: The kit is currently out of stock. Please send me an email (my address is in the top right corner of the page) if you want one. I will put together only a small number of kits at this price, since the display itself is sold by digikey for about $40.

Schematic and board layout are shown below. Preliminary Eagle files can be found here.

The kit is super easy to assemble. It is really impossible to misplace components on the board.
Still, here is some advice:
  • pay attention to the orientation of each of the three integrated circuits, when you insert them in their respective sockets;
  • before soldering the battery holder, put some solder on the big center pad;
  • avoid solder bridges between the USB miniB connector's terminals by wetting their pads (on the bottom side) with a flux pen;
  • it is recommended, for aesthetic purpose, not to solder the FTDI connector to the board; if you need to upgrade the existing software (download from here), you can just hold the 6-pin make header tightly in place while uploading the sketch;

Thursday, July 10, 2014

bGeigie Nano PCB remixed

As I pointed out in my review on Safecast bGeigie Nano kit, the size of the current software already reached the limit of processor's program memory of 30KB or so. From this point on, it is difficult (if not impossible) to add new code features, and that may require drastic code optimization or even disabling existing features.

I thought that the easiest solution to keep this project up-to-date is by upgrading the processor, by entirely replacing the Fio board with an ATmega 644P plus a few extra components (e.g. LiPo charger). This makes the kit a bit more challenging to build, since it requires soldering SMD components, but could also save a few bucks. The device is still Arduino-compatible and programmable, like to Fio, using the FTDI breakout.

Updated Jul 11, 2014: As Rob suggested, I added the XBee module as well. New Eagle files are here.
This is how the bGeigie Nano Plus PCB looks now. (I also added an option for the Fastrax UP501 module, a bit cheaper then the Ultimate GPS breakout, but still a great GPS module (if you can find it on ebay or other sellers)).

The Eagle files for the upgraded bGeigie Nano can be found here.
On the board, the positioning of the modules, switches, headers etc. is the same (except for the Fio, which is now gone).

A few more points:
  • The LiPo charger follows Fio's schematic, using the exact same components.
  • The ATmega644P processor will require burning the bootloader (board has ICSP header).
  • To compile and upload sketches, the Sanguino core files need to be added to the Arduino IDE (as detailed in this post).
  • ATmega1284P, with double the program memory, could be used instead of the 644P, since it has the exact same footprint (and it is pin compatible).

Unfortunately I am short on cash these days, so I hope someone could order the PCB with oshpark (the set of 3 original PCBs was $52 when I ordered them a while ago) and prove the design. I could help with the IDE setup and probably with some software development as well (the first thing that comes to mind is using the whole 128x64 OLED screen, and not just half).

As always, any feedback is appreciated.

Sunday, July 6, 2014

July 2014 release of Wise Clock 4 software

This latest code release includes:
  1. introduction of the two-faced (Kandinsky) feature, on 2 or 4 displays;
  2. fixes related to screen centering for 3 or 4 displays (Big, Stopwatch etc);
  3. fix for Pacman app on 3/4 displays;
  4. fix for Words app on 3/4 displays (so the text does not start scrolling in the middle of the screen);
  5. improved the font definition for digits (effectively making them 5x7 pixels; see photo below);
  6. fix for Score app (swapped button functions);

I am sure that there are still a few bugs to fix.
As well, some improvements would be nice, the most notable being the better use of a screen with 3 or 4 displays, especially for the Big mode, where the time is still shown on the (center) 2 displays. (This would call for spreading out of the digits, or even the definition of a wider font.)

(One of the displays in the 3-display clock is faulty, hence the missing pixel in the bottom 1.)