Older blog entries for jkkroll (starting at number 14)

Steampunk PDA - Project planning

I decided to spend a little more time planning this project than I usually do (a stitch in time and all that…), so I started some design documents on Google docs:

Feature List


Hopefully this will help keep me on track a little better, and avoid scope creep.

Syndicated 2007-07-06 15:20:01 from robotguy.net/Blog

PDA, take two (or is it three?)

While I have been thrilled with the success of the 128×128 LCD, I happened upon an oLED display today that would allow the whole thing to be miniaturized to the point it would fit in a pocket watch:

Pocketwatch PDA

Syndicated 2007-07-04 04:24:08 from robotguy.net/Blog

And now for something a little different…

P.S. I have uploaded a bunch of robot pics to my new Picasa web album here.

Syndicated 2007-04-18 16:34:14 from robotguy.net/Blog

Let there be…. uh…. color

I am having so much fun with this PDA/Tricorder project! Although the 128 X 64 mono LCD is cool and all, I just had to buy the 128 X 128 color LCD from Sparkfun that I’ve had my eye on. I wired it to my ATmega128 breakout board and powered the whole thing with my STK500 set to 3.3V

Voila! I had a nifty color LCD for my project. Here are a few screenshots:

Icons Flower World Setup

I also picked up a few Hammond electronics enclosures ( I love electronics enclosures! I collect them…) from Allied. I get a great deal through work, plus free shipping. I got the 1553B and the 1455J1201. Of course I am also considering putting the electronics into an actual tricorder case. I bought a scratch-build kit from GMProps (look him up on the tricorder props forum), but it proved to be too much for me. Maybe I’ll try a Playmates Tric from Ebay.

Syndicated 2007-03-09 05:20:36 from robotguy.net/Blog

Useable accelerometer data

Here’s a few places I found good stuff about filtering…

  • http://lorien.ncl.ac.uk/ming/filter/filewma.htm
  • http://www.dsptutor.freeuk.com/dfilt1.htm

Syndicated 2007-02-28 00:55:35 from robotguy.net/Blog

Toward a Buttonless Interface

I have been struggling for a while with the lack of user input on the PDA project. I had considered adding an interface through the RF transceiver, but that would mean I would need to be near a PC. I have been unable to find any pushbuttons that I like to install on the face. So I did the next best thing. A sharp sideways tap on the right side of the enclosure brings up a menu, with a small circle next to the selected item:


Tilting the unit in the y direction moves the selection circle, and another tap selects the item. It still needs a bit of tweaking. It seems much easier to tilt in the x direction, because I tilt the unit towards my face when looking at the screen, and that makes the selection circle move down the llist.

Here are links to a few thing I found during my research into tiny user interfaces:

Syndicated 2007-02-27 19:56:00 from robotguy.net/Blog

From the “Because I can” Department…

While waiting for my RF boards to arrive from Sparkfun, I started another project (ooh, look! Something shiny!). I have always liked building things that I could carry around with me, so I decided to build my own PDA. I had the graphic LCD and plenty of processors laying around. I figured adding an RF link back to the PC would not only make it more functional but also help produce code that would be useful for the Spoka project. I also figured that I could combine it with my Tricorder project (notebook pages 3-12) and add as many sensors as I could fit in this little OKW enclosure.
Inside Size Comparison Screenshot PC RF Base

The processor is an ATMega32. I have added a 128 X 64 graphic LCD, a 2.4GHz RF Transceiver, battery-backed real time clock, 2 axis accelerometer, linear Hall effect sensor, and a white led flashlight. The IR receiver is not connected yet. I still plan to add an RGB color sensor and an IR transmitter.

The source code was compiled with WinAVR and is available here. The library for the graphic LCD is from Gregor Horvat (http://www.indata.si/grega/) for the compatible HD61202 controller. After updating a few deprecated commands, it worked first time! I can’t remember where I got the library for the DS1307 clock that I converted for the DS1305. If anyone recognizes it, please let me know. The defines for the NRF24L01 came from S. Brennen Ball.

As you might be able to see from the screenshot, I am currently reading the battery voltage (upper left), magnetic field strength (upper right), x and y acceleration (lower left), and the current time (lower right). The cross-hairs and “bubble” in the center of the screen form a 2-axis level. See the picture of it in my hand for an example with the unit tilted on one axis. The RF transceiver is working well and capable of exchanging data with a PC base unit that connects via serial at 115200 baud.

(BTW, my order arrived from Sparkfun, but I’m having so much fun with this project, I may not get back to Spoka)

Syndicated 2007-02-25 08:51:53 from robotguy.net/Blog

Spoka - Episode IV - A New Hope

OK, so there’s nothing here about hope. I just couldn’t resist the Star Wars reference.

I did however succeed in implementing PWM on the RGB LEDs last night, so I now have 24 bit color for each eye. It turned out to just be a simple interrupt routine. Of course this solution is brute force, and takes up a *!@$load of the processors time (it interrupts every 256 clock cycles). Oh, well. I’ll worry about optimizing it later if I need to. Here’s the interrupt routine if anyone is interested.

if(pwmCounter>rred) LEDPORT|=R_RED;
if(pwmCounter>rgreen) LEDPORT|=R_GREEN;
if(pwmCounter>rblue) LEDPORT|=R_BLUE;
if(pwmCounter>lred) LEDPORT|=L_RED;
if(pwmCounter>lgreen) LEDPORT|=L_GREEN;
if(pwmCounter>lblue) LEDPORT|=L_BLUE;
pwmCounter=1; //reset counter

After a tiny bit of playing around with the color scales, I ended up implementing the first one in the list in the previous post, simply because I could do it programmatically, rather than as a large lookup table. I’m not really happy with the map though. I’d bet the linear optimized map or rainbow looks better (check them out with this java applet). Here’s my colormap function:

void scale1(unsigned char value){
if(value SetRGB((255-(2*value)),2*value,0);

I also ordered a Mirf with a tiny ceramic chip antenna so that it would fit inside the light. Hopefully iy will be here before the weekend, since I’m taking a 4/5 day weekend to work on the project.

Syndicated 2007-02-14 06:04:43 from robotguy.net/Blog

Spoka Pt. III - Choosing current limit resistors & color mapping

I was just realizing that I didn’t put values in for the LED current limiting resistors on the schematic, so I thought I would add a little detail regarding their values and how I chose them. I decided from the start to limit the current through each LED to 15 mA. Each PIN on the AVR can source 40 mA so no problem there, but the entire chip can only source 200 mA total. 7 LEDs X 15 mA = 105 mA. Should be no problem. Plus room to spare when the device is AC powered.

First and easiest was the red. I placed my meter in diode check mode and measured the voltage drop across the LED (Vf) as 1.74V. Measuring the battery output as 3.8V, we get a margin of (3.8-1.74=2.06V) which must be limited to .015A. Dividing the two we get (2.06V/.015A=137Ohms). Putting a 220 and a 330 in parallel gives me (220*330)/(220+330)=132. Close enough.

The blue and green LEDs had too high of a Vf for my meter to read in diode check mode. I knew however that the blue LEDs in the original circuit had a 20 Ohm resistor, so I figured that anything larger should be OK, so I scrounged around and found some 47 Ohm resistors. I soldered these to the LEDs and applied the power, then used the meter to measure the voltage across them. I got 3.16V for the green and 3.07 for the blue.

Green: (3.8V-3.16V=0.64V) (0.64V/0.015A=42 Ohms) Just leave in the 47 Ohms.

Blue: (3.8V-3.07V=.73V) (.73V/.015A=49 Ohms) Again, just leave in the 47 Ohms.

Worst case voltage should be 4.8V when the AC is plugged in. This will give (4.8-1.74)/132= 23mA for the red, (4.8-3.16)/47=35mA for the green, and (4.8-3.07)/47=37mA for the blue. All within the per-pin limit of 40mA. Total output would be (3*23)+(2*35)+(2*37)=213mA. Hmmm, I wouldn’t put out a production unit with numbers like that, but for a hack, it’s not too far off.

I was explaining to my wife the kinds of things I could do with this when it is PC controlled, like changing color according to the speed of a download. This reminded me of an article I saw a while back, “Rainbow LED Indicates Voltage with Color.” This article gives a nice mapping of value to color for the range of 0-255, but it is centered around 128. In other words 128 gives black (all off), 128 gives reddish tints. This might be handy for some things, but not for others. So I did some research on “color scales” and here are a few interesting links:



Syndicated 2007-02-12 20:53:01 from robotguy.net/Blog

Spoka - Part II

(Continued from previous post..)

After removing the LEDs, I marked the outside of the shell to indicate where the eyes and nose were on the rubber cover. Then I modified a small prototyping board to fit into the space, aligning the eyes with the marks made previously. (Notice that the marks are on the same side of the shell as the hole for the plug. Whoops. I had to redo them on the other side)

Marking Open space inside PCB

Then wire the new pcb up, program it and install in the housing for a test (notice my chip-clip programming adapter. It’s handy)…
New Schematic Wired New PCB Step 2Red Green Blue White Mouth

Syndicated 2007-02-12 08:02:05 from robotguy.net/Blog

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