Wednesday, February 27, 2013

3D printed passive amplifiers for the SGS3

My first print!

3D printers had been on my radar for some time, but last year my good buddy Ben reminded me of their existence. At that point the 3D printer bug came up and bit me... hard. I became quite obsessed with the whole scene reading about RepRaps, watching various printer videos (to someone uninterested they must seem like watching paint dry) and such.

There were a few events in down town Raleigh that had printers to show off, but it was not until I went to Splat Space in Durham that I got to use one. This really awesome guy Bill went over the 3D printing ins and outs with me, convinced me that the printer I was looking at purchasing was a good choice, and let me print on his Ultimaker.

My first print was something practical that I had worked designed and - after showing Bill - revised a few times. The object was/is a megaphone of sorts for a Samsung Galaxy SIII. The idea is to collect all the sound as it exits the rear of the phone, and redirect it forward using a cone shaped cavity. Amplification without power by means of focusing energy in one direction.

Here is a 3D rendering of the first printed design (on the phone) and the latest design (the two not on a phone):

Here are some pictures of the actual printed pieces:

Much to my surprise the print came out great on the first try. I figured the first design I tried would not work at all, but the passive booster worked so well that at full volume it was painful to listen to!

For the non believers here is a video demonstration (this was probably a poor song choice, quite input still the change is noticeable).

Here are the "source" files for the objects

Note:  The files are licensed under the GPLv3. Feel free to post them and reuse them wherever, but it is probably in violation of the GPL to post them (or derivatives) to a site that does not maintain the GPL license.

Monday, February 25, 2013

Meltdown (Markdown Extra Live Toolbox)

Monday, February 18, 2013

3D printing WiFi antenna enhancers

I used to build parabolic dishes for WiFi out of cardboard, soda cans, and hot glue. They worked rather well too. This is the template I used.

That was then. Nowadays when I tinker I get to tinker with a cool Mosaic M2 so when the WiFi connection to my xbmc machine felt a little weak (in a closet a few rooms away from the router) I decided to break out that trusty old template and get to modeling.

Here are the "source" files used to create the dishes:
Note:  The files are GPLv3 licensed. Feel free to post them wherever, but it is probably in violation of the GPL to post them (or derivatives) to a site that does not maintain the GPL license.

The results are great. I went from 1200-1500KBps (~12mbps) to 2000-2500KBps (~20mbps) on an old WRT54G.

Wednesday, March 23, 2011

More laziness with the XBMC Remote Android App

The XBMC android app is great. I mean really really great. It might just be the best android app on my shiny new Atrix. There is/was one problem though. While the wake on LAN properly wakes my box up, the app has no suspend feature.

Hmm... eerily similar to the situation I ran into a few weeks ago. Luckily the app is GPL and I can have a go at fixing things.

XBMC has a secure auth http port exposed and a second unauthed raw command port for LAN only use. The patch below adds a suspend function that sends json to the raw port, and adds a button on the home screen to call the new function. For now this is just a simple get it done hack (hardcoded hostname/port, not following the code style/convention), but it would be cool to build a nice full featured "Shutdown" menu that enables exit, shutdown, suspend, etc. functionality.

Maybe later. Need sleep now... Self.Suspend()

$ svn di src/org/xbmc/android/remote/presentation/controller/
Index: src/org/xbmc/android/remote/presentation/controller/
--- src/org/xbmc/android/remote/presentation/controller/ (revision 759)
+++ src/org/xbmc/android/remote/presentation/controller/ (working copy)
@@ -21,6 +21,11 @@


import java.util.ArrayList;
import java.util.HashMap;
import java.util.Observable;
@@ -103,8 +108,8 @@
private static final int HOME_ACTION_RECONNECT = 5;
private static final int HOME_ACTION_WOL = 6;
private static final int HOME_ACTION_TVSHOWS = 7;
+ private static final int HOME_ACTION_SUSPEND = 8;

private IInfoManager mInfoManager;

private static final String TAG = "HomeController";
@@ -229,6 +234,7 @@
homeItems.add(new HomeItem(HOME_ACTION_NOWPLAYING, R.drawable.icon_home_playing, "Now Playing", "See what's"));
+ homeItems.add(new HomeItem(HOME_ACTION_SUSPEND, R.drawable.icon_home_power, "Suspend", "Invoke"));

final ArrayList offlineItems = new ArrayList();
@@ -310,6 +316,9 @@
+ doSuspend();
+ break;
if (intent != null) {
@@ -318,6 +327,18 @@

+ private void doSuspend() {
+ try {
+ final Socket mySocket = new Socket("myth.lan", 9090);
+ final PrintWriter out = new PrintWriter(mySocket.getOutputStream(), true);
+ out.println("{\"jsonrpc\": \"2.0\", \"method\": \"System.Suspend\", \"id\": \"1\"}'jsonrpc': \"2.0\", 'method': \"VideoLibrary.ScanForContent\", 'id': \"1\"");
+ out.close();
+ mySocket.close();
+ } catch (IOException e) {
+ }
public void update(Observable observable, Object data) {
if (data instanceof BroadcastListener.Event) {
BroadcastListener.Event event = (BroadcastListener.Event)data;

Wednesday, March 9, 2011

XBMC, /proc/acpi/wakeup, and instant resume

I got one of these guys to control my Fedora XBMC HTPC without wires and without having a large keyboard on the coffee table.

There was one nagging issue though. To be completely lazy I needed a remote power switch. Specifically I needed a way to wakeup the box from suspend.

/proc/acpi/wakeup to the rescue! I quickly found that USB2 was the bus (terminology?) that my wireless keyboards dongle was attached to. Great! But do to the way /proc/acpi/wakeup and the wireless dongle work I was left with a problem... as soon as the computer suspended it resumed. No amount of acpi conflict resolution seemed to work for me (as discussed here

Whats a hacker to do? Hack of course :-D

I patched the XBMC code a few times to provide a delay when the suspend function was called (I figured the remote needed to be fully powered off). No good. So I patched XBMC again to not use its built in suspend functionality, but instead call out to an external shell script. No more compiling/test/compiling/etc. Yay!

--- xbmc-10.0-Dharma/xbmc/utils/Builtins.cpp 2010-12-17 01:17:41.000000000 -0500
+++ xbmc-10.0-Dharma-delay/xbmc/utils/Builtins.cpp 2011-03-06 14:05:57.747094861 -0500
@@ -84,6 +84,10 @@


using namespace std;
using namespace XFILE;
@@ -254,7 +258,16 @@
else if (execute.Equals("suspend"))
- g_application.getApplicationMessenger().Suspend();
+ pid_t child_pid = fork();
+ if (child_pid == 0) {
+ char *args[] = {"/usr/bin/xbmc-delay", (char *) 0};
+ execvp (args[0], args);
+ return(0);
+ } else {
+ wait(NULL);
+ }
+ kill(child_pid, SIGKILL);
+ //g_application.getApplicationMessenger().Suspend();
else if (execute.Equals("quit"))

Now I could edit the shell script and test rather quickly (no need to rebuild and install). I found that with one suspend the dongle was still active enough to wake the box. Even large delays (so I could turn the remote off before the box was going down) did not help.

What works? Two back to back suspends. Why? I think it has to do with the way that usb subsystems come back online after a suspend. The dongle needs to stop mucking around on the usb bus to stop waking the machine up. While suspended the dongle certainly quits doing stuff. Thus when the second suspend occurs the dongle has settled down, and it does not wake the box up until I power the remote on.

The bash script is stupid simple
sleep 1
sudo pm-suspend
sudo pm-suspend

Fun stuff...