Linux VNC and Mac OS X Screen Sharing

I’ve found that in order to get x11vnc to work with the Mac OS X built-in VNC client (“Screen Sharing Application”), there options are required when starting the VNC server:

$ x11vnc -display :0 -rfbauth /home/pi/.vnc/passwd -shared -rfbversion 3.3 -forever -bg

The -shared option is key here. Judging by the log on the VNC server, I think Mac OS X will attempt multiple connections.

For what it’s worth, here’s also how to auto-start the VNC server when the user logs into the LXDE desktop. Copy and paste this to ~/.config/autostart/x11vnc.desktop:

[Desktop Entry]
Exec=x11vnc -display :0 -rfbauth /home/pi/.vnc/passwd -shared -rfbversion 3.3 -forever -bg

Working around KiCAD Printing Issues

I’m having issues printing from KiCAD, specifically Pcbnew, on Ubuntu 15.04. I’ve seen similar things on earlier versions, and also found this bug report. Even though the bug report is closed and I’m using the right wx version, the problem persists for me. So I’ve searched for a workaround.

Luckily, “plotting” from KiCAD works which makes it generate a PostScript file for each layer.

However, I need the “Edge Cuts” layer and the bottom copper layer printed on a single page. The reason is that I’m printing my layouts on transparent film, and I’m using alignment marks on the edge cuts layer to help me tape two prints on top of each other. This increases the opaqueness of my print to a point where it’s usable for me.

So here’s the steps it takes to get my PCB layout to a decent print:

  1. “Plot” the required layers from Pcbnew, leaving a bunch of PostScript files on disk.
  2. Convert the PostScript files to PDF:
    $ for ps in *.ps ; do ps2pdf $ps ; done
  3. Use pdftk to generate a single PDF from the relevant layers like this:
    $ pdftk layout-B_Cu.pdf background layout-Edge_Cuts.pdf output layout.pdf

Update: There’s an option to include the “Edge Cuts” layer when plotting. Simply uncheck the “Exclude PCB edge layer from other layers” option as highlighted in the screenshot below.

Ubuntu 14.04, ThinkPad W520 and multiple Monitors

Here’s a quick reminder of the commands that I use to switch between a single monitor setup (internal laptop screen) and two external, DVI-attached monitors on my ThinkPad W520 running Ubuntu 14.04 (x86_64).

In order to switch to single-screen setup:

phs@W520:~$ disper -s -d DP-2 -r auto
phs@W520:~$ disper -s -d LVDS-1 -r auto

Switching to the two external monitors:

phs@W520:~$ disper -s -d DP-2 -r auto
phs@W520:~$ disper -e -d DP-2,DP-3 -r auto

All of this uses the stock, Ubuntu-provided driver. Didn’t have much success with the nVidia drivers (from the repositories) on this laptop.

Programming Avnet Spartan 3A FPGA Eval Board with Linux

I own a small FPGA Board by Avnet with a Spartan 3A FPGA on it. The board is nice, but unfortunately, the flash chips on the board aren’t on the JTAG chain. Instead, there is a small PSoC microcontroller that lets you programm the flashes via UART. There is a Windows tool to perform that programming which is shipped with the board. Here’s what I did to program the SPI configuration flash on Linux.

Via the FPGALibre site, I found a link to a tool called ASTriAEKiPro, which allows me to write to the FPGA SPI Configuration flash via UART and the PSoC microcontroller.

Compiling the tool is as simple as running this command:

$ make

To erase the SPI configuration flash, I used this command:

$ ./astriaekipro -p /dev/ttyACM0 -e
Avnet Spartan 3A Eval Kit Programmer v1.2.1
Copyright (c) 2009 Salvador E. Tropea 
Copyright (c) 2009 Instituto Nacional de Tecnolog�a Industrial
Embedded BPI server provided by Avnet Inc.

Erasing the memory, be patient (>1 minute) ...

To write a configuration to the SPI flash:

$ ./astriaekipro -p /dev/ttyACM0 -w 
  -b ~/sandbox/avnet_lpc/projects/13.3/avnet_lpc/avnet_i2c.bit 
Avnet Spartan 3A Eval Kit Programmer v1.2.1
Copyright (c) 2009 Salvador E. Tropea 
Copyright (c) 2009 Instituto Nacional de Tecnolog�a Industrial
Embedded BPI server provided by Avnet Inc.

Writing 235820 bytes to the serial flash, offset 0x0000000
Erasing: sector   3 (100.00 %)
Bytes written:   235820 (100.00 %)
All written!

Edit Samsung TV Channel List on Linux

Samsung TVs suck when it comes to sorting the channel list. The work-around is to transfer the channel list to a PC and edit/sort it there. To edit the channel list on Linux, I found a tool called "SamyGO ChanEdit" quite useful. Downloadable via this link.

The tool requires SWT which is installed in /usr/lib/java on my system. To start the tool, used the following command:

java -classpath .:/usr/lib/java/swt-gtk-3.8.2.jar:SamyGO-ChanEdit-v54cd.jar gui.Main

Ubuntu 11.10 on Lenovo W520

At work, I got a new laptop — a Lenovo W520. It came with Ubuntu 11.10 ("Oneiric Ocelot") pre-installed by the support team. My first impression was that it worked pretty well, but I quickly discovered that I couldn’t change the brightness of the display through the Fn+Home/End keys.

The W520 uses this “Optimus” technology with an integrated on-board graphics card plus a separate NVIDIA card, where both cards can be switched on-the-fly — on Windows. The default installation used the high performance card and I suspected that the video card driver was keeping me from adjusting the brightness. As it turns out, after switching to the on-board Intel card, things worked fine. Here’s what I needed to do:

First, I needed to disable the NVIDIA card in “the BIOS” and switch to the on-board card. There’s an option somewhere under “Setup”, then “Display”, if I recall correctly.

Next, I changed the video card section in my /etc/X11/xorg.conf to read this:

Section "Device"
  Identifier "Device0"
  Driver "intel"
  Option "Shadow" "True"
  Option "DRI" "True"

In fact, I added the two Option lines later on and only changed the Driver line at first. I then discovered that most of the little try icons in the upper right corner of the Gnome desktop wouldn’t show anymore. A look at /var/log/Xorg.0.log turned up some errors and running glxinfo yielded lines like these:

Xlib:  extension "GLX" missing on display ":0.0".

Luckily, someone else ran into the same issues over at As indicated there, I also ran these commands:

$ sudo apt-get purge nvidia*
$ sudo apt-get install --reinstall xserver-xorg-video-intel 
    libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core
$ sudo dpkg-reconfigure xserver-xorg
$ sudo update-alternatives --remove gl_conf /usr/lib/nvidia-current/

The first command hinted that some "ubuntu-desktop" package would also be removed. I don’t know what that is, but I don’t miss it, yet. Anyways, after a final reboot, the brightness adjustment now works and all my tray icons are back in place.