difference between insmod and modprobe

Time to refresh memory:

modprobe reads the modules and its dependencies from /lib/modules/$(uname -r)/modules.dep or modules.dep.bin.  modprobe is a smarter tool which will also load the dependent modules.

modprobe accepts the name of a .ko file in /lib/modules/$(uname -r) and aliases (modules.alias.bin).

insmod takes file name or the exact paths to files. The module does not have to reside in /lib/modules/$(uname -r), but dependencies are not automatically loaded. This is the lower program used by modprobe to load modules.

rmmod removes a kernel name based on the name from /proc/modules. This name does not necessarily have to be the same as the one passed to modprobe (for the nvidia-current file, this is nvidia for example).

modinfo accepts a filename, or the filename without .ko suffix in /lib/modules/$(uname -r).

guake - a cool top down terminal for Gnome

http://guake.org/

It's just cool....
try it:

# sudo aptitude install guake

nohup - run a command immune to hangups (terminal close)

Say you're on business trip, ssh to a remote server, run a command to compile some huge source code which take hours, or process date which takes days, but then you need to close your laptop and run the next site.  Closing the terminal will also kill all the process you started.  What should you do?

nohup is is there to help you.:

NAME
       nohup - run a command immune to hangups, with output to a non-tty

SYNOPSIS
       nohup COMMAND [ARG]...
       nohup OPTION

DESCRIPTION
       Run COMMAND, ignoring hangup signals.

Take an example of compiling a fresh configured buildroot, depends on the packages selected it takes hours/days to download the sources and compile:

EXAMPLE
       $ nohup make buildroot &

Then the buildroot compilation will continue after you close your terminal/laptop.

Audacious Headless and Keyboard Shortucts

Audacious is an open source audio player, a descendant of XMMS, light-weighted and very similar to MS Windows winamp.

However, by default it does not recognize keyboard shortcuts play/pause/prev/next.

In Audacious preferences (right click on the the right lower corner "a" logo, in the pop-up menu choose preference), -->plugins  --> general tab --> check the "Global Hotkey" plugin, then it would recognize those shortcut keys.  I would prefer Audacious to enable this by default..

Gaming mouse too fast (sensitive) under Ubuntu Linux

I've got a set of RAPOO keyboard and mouse.  I bought it just because it's a set of really compact and quiet keyboard and mouse, but after I got it I figured it's for gaming so the speed is crazily fast when I use it under Linux.  I went to the "Mouse and Touchpad" to turn Acceleration and Sensitivity to the minimum value but it doesn't work.  Finally I've done the following to slow it down.

gideon@gideon-desktop-i5:~$ xinput --list --short
⎡ Virtual core pointer                     id=2 [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer               id=4 [slave  pointer  (2)]
⎜   ↳ RAPOO RAPOO 5G Wireless Device           id=9 [slave  pointer  (2)]
⎜   ↳ MemsArt MA144 RF Controller              id=11 [slave  pointer  (2)]
⎜   ↳ MemsArt MA144 RF Controller              id=12 [slave  pointer  (2)]
⎣ Virtual core keyboard                    id=3 [master keyboard (2)]
    ↳ Virtual core XTEST keyboard              id=5 [slave  keyboard (3)]
    ↳ Power Button                             id=6 [slave  keyboard (3)]
    ↳ Power Button                             id=7 [slave  keyboard (3)]
    ↳ RAPOO RAPOO 5G Wireless Device           id=8 [slave  keyboard (3)]
    ↳ MemsArt MA144 RF Controller              id=10 [slave  keyboard (3)]
    ↳ MemsArt MA144 RF Controller              id=13 [slave  keyboard (3)]
gideon@gideon-desktop-i5:~$ xinput --set-prop 9 "Device Accel Velocity Scaling" 1
gideon@gideon-desktop-i5:~$ xinput --set-prop 9 "Device Accel Constant Deceleration" 2

For your mouse, the last 2 commands you may need to play around with the numbers to find the optimum value.

DS89C450 SDCC getchar() function

After the putchar() function you probably need the getchar() function.  The function is also quite simple. Just check the Receive Interrupt flag instead of Transmit Interrupt in the putchar().  I'm using mode 0 for the serial port, the RI_0 is set at the end of the 8th bit. When the flag is set, clear it then read and return the data:

char getchar(void) {
        char c;
        while (!RI_0)
        ;
        RI_0 = 0;
        c = SBUF0;
        return c;
}

If you want to read a line input you can use gets():

char line[100];

gets(line);

DS89C450 SDCC serial init and printf putchar functions

sdcc is a very handy tool but it isn't magic.  For embedded system even a "hello world" printf function isn't easy. If you just put printf in your code and ask sdcc to compile, it will complain because it doesn't know how the system connects to the serial port:

?ASlink-Warning-Undefined Global '_putchar' referenced by module 'hello'
make: *** [hello] Error 1

You get the same error for similar printf stdio.h functions (e.g. vprintf, sprintf, vsprintf, puts etc...)

The solution is easy; just define the putchar() function to describe which buffer (e.g. UART0 or UART1) the characters should go to.  Here is my example code of "Hello World" and blinking some LED on the DS89C450 evaluation kit:

#include <stdio.h>
#include "sdcc_reg420.h"

void delay(void)
{
 unsigned int i, j;

 for(j=0; j<12; j++)
 {
  for(i=0; i<3000; i++)
  {
  }
 }
}

void serialInit()
{
 TMOD = 0x21;    // Timer 1: 8-bit autoreload from TH1
 TH1 = 220;      // 14400 baud rate
 CKMOD = 0x38;   // Use system clock for timer inputs
 T2CON = 0x00;   // Serial 0 runs off timer 1 overflow
 TCON = 0x50;    // Enable timers 0 and 1
 SCON0 = 0x50;   // Enable serial port 0
 SBUF0 = ' ';
}

void putchar (char c) {
 while (!TI_0) /* assumes UART is initialized */
 ;
 TI_0 = 0;
 SBUF0 = c;
}

void main(void)
{
 serialInit(); // Initialize serial port 0

 printf("\rHello World!!\n");

 while(1)
 {
  P1 = 0x01;
  delay();
  P1 = 0x02;
  delay();
  P1 = 0x04;
  delay();
  P1 = 0x08;
  delay();
 }
}

Then it works! Download your firmware to the evKit and then you can see the "Hello World" displaying on your terminal! If nothing comes up then check if the LED are blinking. If LED are not blinking then the firmware is not running.. something is probably really wrong. I set 14400 as baudrate because the evKit uses the same baudrate for the in-system programming. I just don't want the hassles of changing the baudrate of my terminal all the time. If you need the register file sdcc_reg420.h of the above example code, you can get it in the following link:

http://www.maximintegrated.com/app-notes/index.mvp/id/3477

Only this document was written some time ago and now sdcc will warn it uses some deprecated macros. But the file still works fine and updating the keywords are trivial task.

git clone --mirror and update

To create a git repository mirror is fairly easy:

$ git clone --mirror ssh://user@example.com/path/to/repo

To update the mirror from the original source:

$ git remote update

ssh-add "Could not open a connection to your authentication agent"

I came accross some occurence when I use ssh-add to add a ssh key it gives me the following error:

Could not open a connection to your authentication agent.



and the following command did the trick sometimes...

$ exec ssh-agent bash

but I still have the problem when I use ssh-add under Cygwin in Windows system.... couldn't find a solution :(

Linux serial baud 14400 and DS89C450 development

For some freaking reason Linux couldn't support 14400 baud rate on it's serial connection.  I was doing some development based on Maxim's DS89C450 , as it is one of the highest performance 8051 compatible microcontrollers in the market. The nice thing of this DS89C450 is that it has a boot ROM which allows me to program the chip using serial port (instead of an expensive programmer).  However, the boot ROM only allows COM port connections at 14400 and Linux doesn't support this baud rate. (dear Maxim friends, can you change the baud rate to a standard one?)

I was desperate and trying through different bauds, surprisingly I found that it can work under 2400bps instead of 14400. (Anyone can explain to me why?)

If you are interested, there are a few more further readings of development using DS89C450 under Linux:

• In-System programming of Maxim 8051-based Microncontrollers
• SDCC C Compiler is free and also available under Linux
• My favorite FTDI USB to serial converter cable - it works perfectly under Mac, Win and Linux, don't use the Polific it's a waste of time....

Ben Krasnow - Nice tutorial on transistor circuits

http://www.youtube.com/watch?v=8DMZSxS-xVc

Arch Linux: systemctl dhcpcd netcfg problem

I think the Arch Linux dhcpd / dhcpcd thing is kinda broke...
I read many installation guide which says to start dhcp use the following command but it NEVER works for me:

# systemctl enable dhcpcd@.service 

eth0 or enp2s1 whatever won't work.  I don't know what the heck is enp2s1 in my system...

Anyway, this is what I do to fix it(mine is just VMware NAT network):

1. cp /etc/network.d/examples/ethernet-dhcp /etc/network.d/mynetwork
2. vi /etc/network.d/mynetwork  , modified line INTERFACE='enp2s1'
3. try in root, netcfg mymetwork, see if it can fetch IP properly
4. if everything looks good, # systemctl enable netcfg@mynetwork

It should create the symbolic link.  Then reboot to see if it works properly...

VirtualBox UUID already registered

Stupid VirtualBox after you copied it and use it again it will complain the UUID already registered. Use the below Linux command to assign it a new random UUID:

$ vboxmanage internalcommands sethduuid arch.vdi

BloggerPaste: convert your code to HTML

For many times the blogger editor messed up my code when I paste it here.  Obviously blogger is not intended for programmer.

I found an excellent tool to convert my code into HTML so that I can put it correctly here.

http://francois.schnell.free.fr/tools/BloggerPaste/BloggerPaste.html

Linux Mint 14 and Ubuntu 12.10 Chinese fonts Blur problem

Wenq.org offered an excellent tool to generate the .fonts.conf

http://wenq.org/cloud/fcdesigner_local.html

And also for the Chinese fonts packages

# aptitude install ttf-wqy-microhei ttf-wqy-zenhei xfonts-wqy

e.g. I used the tool to generate the below config file, save to ~/.fonts.conf and now the Chinese fonts looks much clear to me.

To download my file https://docs.google.com/file/d/0B7j0X0cOW5wTWnV2N3Y3NS1FeVE/edit

Or copy and paste here (Hope blogger won't do weird thing to mess up my code):

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<!-- created by WenQuanYi FcDesigner v0.5 -->
<match>
 <test name="family"><string>sans-serif</string></test>
 <edit name="family" mode="prepend" binding="strong">
  <string>DejaVu Sans</string>
  <string>WenQuanYi Bitmap Song</string>
  <string>WenQuanYi Micro Hei</string>
  <string>WenQuanYi Zen Hei</string>
  <string>Liberation Sans</string>
  <string>Droid Sans</string>
   <!-- Please install WenQuanYi Bitmap Song first -->
 </edit>
</match>
<match>
 <test name="family"><string>serif</string></test>
 <edit name="family" mode="prepend" binding="strong">
  <string>DejaVu Serif</string>
  <string>WenQuanYi Bitmap Song</string>
   <!-- Please install WenQuanYi Bitmap Song first -->
  <string>AR PL UMing CN</string>
  <string>AR PL SungtiL GB</string>
  <string>WenQuanYi Zen Hei Sharp</string>
  <string>AR PL UMing TW</string>
  <string>Liberation Serif</string>
  <string>Bitstream Charter</string>
  <string>Droid Serif</string>
 </edit>
</match>
<match>
 <test name="family"><string>monospace</string></test>
 <edit name="family" mode="prepend" binding="strong">
  <string>WenQuanYi Zen Hei Sharp</string>
  <string>WenQuanYi Zen Hei Mono</string>
  <string>WenQuanYi Micro Hei Mono</string>
  <string>DejaVu Sans Mono</string>
  <string>Droid Sans Mono</string>
  <string>Liberation Sans Mono</string>
   <!-- Please install Liberation Sans Mono first -->
  <string>AR PL UMing TW</string>
 </edit>
</match>
</fontconfig>

Viewnior fast image viewer

Just found Viewnior a pretty good image viewer, much faster image loading than the Ubuntu default image viewer. It doesn't need to import images like shotwell, and it allows left and right button to scroll to the next image.

so much to ask for a simple image viewer huh?

http://xsisqox.github.com/Viewnior/index.html