http://www.xargs.com/pic/c-faq.html

Cheers!

Part of the problem is Microchip’s documentation.  The C18 libraries were supposed to streamline a lot of programming for the PIC… and for the most part, it did; Microchip just hasn’t done a good job of making sure to completely document it all.

Anyway, below follows a pure-C18 example of an echo server, operating on a PIC18, with a MAX232 serial converter in between the PIC and my PC.  First the code, and then some discussion.

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#include <p18cxxx.h>
#include <usart.h>
 
void main(void)
{
	char test = 't';
	TRISCbits.RC7 = 1;
	TRISCbits.RC6 = 0;
	OSCCON = 0b11100010;
	OSCTUNEbits.PLLEN = 0;
 
        while (!OSCCONbits.IOFS);
 
	baudUSART(BAUD_IDLE_CLK_LOW & 
         	  BAUD_AUTO_OFF & 
         	  BAUD_8_BIT_RATE & 
         	  BAUD_IDLE_RX_PIN_STATE_HIGH &
	          BAUD_IDLE_TX_PIN_STATE_HIGH);
 
	OpenUSART(USART_TX_INT_OFF &
          	  USART_RX_INT_OFF &
        	  USART_ASYNCH_MODE &
        	  USART_EIGHT_BIT &
        	  USART_CONT_RX &
        	  USART_ADDEN_OFF &
        	  USART_BRGH_HIGH, 207);
    while (1) {
        WriteUSART(test);
	while(!DataRdyUSART());
        test = ReadUSART();
        Nop();
    }
}

If you were to try and copy/paste this code, there is a chance that it would work, out-of-the-box.  If it doesn’t work, presuming your hardware & MAX232 circuits are correct, the most likely culprit is the OSCON configuration.

As with all forms of communication, analog or digital, timing is the key.  There are two important timing lines in the above code; first, when we configure the oscillator inside of the PIC:

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OSCCON = 0b11100010;

And when we tell the USART module how fast we are operating:

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.... USART_BRGH_HIGH, 207);

The first bit, the OSCCON register setting, is configuring my PIC’s clock to operate at 8 Mhz.  This may be different for you, depending on what model PIC you are using – make sure to check your datasheet! The second bit includes the number ’207′ – this is the number that the PIC uses to calculate how fast you expect it to operate on the RS232 line – i.e., your baud rate.

The datasheet for your PIC should have a formula to help you calculate that number, probably in a section titled something like ‘Baud Rate Generator’.  Figure out what baud rate you want to operate at, and use the appropriate number for it!

This is a very brief and not a very in-depth discussion of this topic, but I had trouble finding a decent example online to use as a starting place; I’m hoping this post serves that role for some other poor hacker fighting with the C18 docs =)

Cheers!

Now that my defense is all said and done, I created an ETD template / example file for theses and dissertations for modern LaTeX distributions.  It contains all of the necessary ETD formatting guidelines, as well as many of the packages that a technical thesis / dissertation may require and some good default settings.

You can see the template here:

http://git.hokietux.net/?p=latex.git&a=blob&f=etd_template/etd_template.tex

And the Git source tree summary is here:

http://git.hokietux.net/?p=latex.git&a=summary

If you find this useful, or if you have any comments / suggestions, please let me know!

Here are some of the changes made since the last post:

• The background canvas is now a lighter color, and the navigation bar is now darker.
• Bullets fade from maroon to orange depending on the indent level.
• The source code now includes two logos, the VT logo and the Wireless@VT logo, for anyone that wants to use them.
• Updated the example presentation file.
• Added a README for people who want to tweak it.
• Changed the color of the block example backgrounds.

Here are a few pictures that illustrate what it looks like:

Title Slide

Table of Contents

Basic Slide

Bullet Points

The example presentation in the beamer-example/ directory of the source tree has more slides, including a table, figure, and equation, but the above should be enough to give you an idea of the theme’s general appearance.

The source code is available here: http://git.hokietux.net/?p=latex.git&a=summary

Let me know if you have any comments / suggestions, and enjoy! =)

I grabbed an example presentation from Jean-Etienne, and compiled it using the Hokie theme.  The four images below show what some of the basic slides look like:

The title slide of the default layout.

The outline slide of the default layout.

An example basic slide using the default layout.

An beamer example block in a slide.

Using the theme is pretty simple – grab the files from my Git repository, put them in your project directory, and then simply use the command:

usetheme{Hokie}


…in your *.tex file.  You can see all of this in the beamer-example directory, as well.

There are three available layouts that I have tested the theme with, and they all work well.  If you look inside of ‘beamerthemeHokie.sty’, you will see three theme lines, only one of which isn’t commented out.  Try each of them, and choose the one you like the most!  I’ll post pictures of the rest as soon as I have time.

Head here for the code!

If you have any bug reports, suggestions, or comments, please let me know!

1. Getting it to let me insert breaks into paragraphs.
2. Writing code in blog posts. Not writing HTML code to create the blog post, but actually writing code that is meant to be displayed in the blog post.  This blog is supposed to be about technology, after all.

Just searching around reveals that I am not alone in either point.  I have pretty much given up on the first one, and occasionally just have to manually insert “<br />”.  There are currently over 1,150 posts on the WordPress forums related to this, and it’s mind-blowing that this is still so freaking difficult.  It’s been a long, long time, though, and it still hasn’t been changed, so I’m pretty sure it won’t ever be.  Why not, I know not.

In terms of #2, I have finally found a semblance of a solution, using a combination of three plugins, and some special rules.  I installed all three of the following plugins:

• WP-Syntax
• WP-Syntax Editor Integration Plugin (Warnung: Seite in Deutsch)
• Visual Code Editor

When I want to paste code into a blog post, I do it in the HTML editor (this part is critical), paste the code, then highlight the code and click the little button that one of those plugins adds.  Now then, DON’T FREAKING TOUCH IT.

I’ve tried to paste in code not following that exact procedure, and once it actually inserted PHP comment tags around my entire code block.  Also, if you try to paste in code while in the visual editor, it adds all kinds of ridiculous ‘div’ and ‘p’ blocks around the text, and totally mucks up the code block displays.

Anyways, I hope this helps someone else that is suffering while trying to post code.

Please note that this is _not_ the git-php located on Google code.  That is a different project, and appears to be abandoned.

As the GitPHP homepage states, GitPHP looks almost exactly like Gitweb, but has a few extras (most noticeably in the form of a little balloon that comes up showing more information about commits on mouse-hover).

GitPHP works with Gitosis in the same way the Gitweb does.  In your Gitosis configuration, you can manually delegate which repositories to publish to the web, or just have GitPHP publish all of them.  If you want to only publish select repositories (which is what I do – I actually only have one public repository), then you need to configure Gitosis appropriately.  For example, to publish the repository ‘configs’, then you must define ‘gitweb = yes’ in your Gitosis configuration file:

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[configs]
members = HokieTux
writeable = admin
gitweb = yes

You can download GitPHP either via the tarball published on the homepage, or via the author’s own GitPHP page!  There is no build process – just unpack the source to the directory from which your web server will serve the content.  For me, (<3 ArchLinux), that’s /srv/http/gitphp/.  Now, we need to make sure that the user/group of your webserver process can access the GitPHP directory.  This is easy.  If your web server user name and group is apache:apache, then:

$ sudo chown -R apache:apache /srv/http/gitphp

Done!  Now, let’s make your configuration file.  Head into gitphp/config/, copy gitphp.conf.php.example to gitphp.conf.php.  The list of options that are available to you are described pretty clearly in gitphp.conf.defaults.php, if you are curious.  For most people, a pretty bare configuration file will work fine.  I added some things to mine, which you can see below:

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<?php
/**
 * GitPHP Config file
 *
 * Copy this example file to config/gitphp.conf.php
 *
 * @author Christopher Han <xiphux@gmail.com>
 * @copyright Copyright (c) 2010 Christopher Han
 * @package GitPHP
 * @subpackage Config
 */
 
/*
 * projectroot
 * Full directory on server where projects are located
 */
$gitphp_conf['projectroot'] = '/srv/git/repositories/';
 
/*
 * exportedonly
 * When listing all projects in the project root,
 * (not specifying any projects manually or using a project list file)
 * set this to true to only allow repositories with the
 * special file git-daemon-export-ok (see the git-daemon man page)
 */
$gitphp_conf['exportedonly'] = true;
 
 
/*
 * cache
 * Turns on template caching. If in doubt, leave it off
 * You will need to create a directory 'cache' and make it
 * writable by the server
 */
$gitphp_conf['cache'] = true;
 
/*
 * objectcache
 * Turns on object caching.  This caches immutable pieces of
 * data from the git repository.  You will need to create a
 * directory 'cache' and make it writable by the server.
 * This can be used in place of the template cache, or
 * in addition to it for the maximum benefit.
 */
$gitphp_conf['objectcache'] = true;
 
/*
 * cacheexpire
 * Attempts to automatically expire cache when a new commit renders
 * it out of date.
 * This is a good option for most users because it ensures the cache
 * is always up to date and users are seeing correct information,
 * although it is a slight performance hit.
 * However, if your commits are coming in so quickly that the cache
 * is constantly being expired, turn this off.
 */
$gitphp_conf['cacheexpire'] = true;
 
/*
 * cachelifetime
 * Sets how long a page will be cached, in seconds
 * If you are automatically expiring the cache
 * (see the 'cacheexpire' option above), then this can be set
 * relatively high - 3600 seconds (1 hour) or even longer.
 * -1 means no timeout.
 * If you have turned cacheexpire off because of too many
 * cache expirations, set this low (5-10 seconds).
 */
$gitphp_conf['cachelifetime'] = 3600;
 
/*
 * objectcachelifetime
 * Sets how long git objects will be cached, in seconds
 * The object cache only stores immutable objects from
 * the git repository, so there's no harm in setting
 * this to a high number.  Set to -1 to never expire.
 */
$gitphp_conf['objectcachelifetime'] = 86400;
 
 
/*******************************************************
 * Paths to php libraries
 */
 
/*
 * smarty_prefix
 * This is the prefix where smarty is installed.
 * If an absolute (starts with /) path is given,
 * Smarty.class.php will be searched for in that directory.
 * If a relative (doesn't start with /) path is given,
 * that subdirectory inside the php include dirs will be
 * searched.  So, for example, if you specify the path as
 * "/usr/share/Smarty/" then the script will look for
 * /usr/share/Smarty/Smarty.class.php.
 * If you specify the path as "smarty/" then it will search
 * the include directories in php.ini's include_path directive,
 * so it would search in places like /usr/share/php and /usr/lib/php:
 * /usr/share/php/smarty/Smarty.class.php,
 * /usr/lib/php/smarty/Smarty.class.php, etc.
 * Leave blank to just search in the root of the php include directories
 * like /usr/share/php/Smarty.class.php, /usr/lib/php/Smarty.class.php, etc.
 */
$gitphp_conf['smarty_prefix'] = '/srv/http/gitphp/lib/smarty/libs/';
 
/*
 * geshiroot
 * Directory where geshi is installed, only applies if geshi is enabled
 * NOTE: this is the path to the base geshi.php file to include,
 * NOT the various other geshi php source files!
 * Leave blank if geshi.php is in the gitphp root
 */
$gitphp_conf['geshiroot'] = '/srv/http/gitphp/lib/geshi/';

The most important options, in terms of just getting up and running, are the first two options: ‘projectroot‘ and ‘exportedonly‘.  Set those properly, and you should be all done!

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server {
    listen               80;
    server_name     git.hokietux.net;
    root                /srv/http/gitphp;
    index               index.php;
 
    # This is some magic to try to serve a php file without rewriting anything. It makes
    serving some content much faster.
    location / {
        try_files $uri $uri/ /index.php?q=$uri&$args;
    }
 
    location ~ .php$ {
        fastcgi_split_path_info ^(.+.php)(/.+)$;
        include        fastcgi.conf;
        fastcgi_pass   unix:/var/run/php-fpm/php-fpm.sock;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME  /srv/http/gitphp/$fastcgi_script_name;
        fastcgi_cache_valid any 1m;
        fastcgi_intercept_errors on;
}

There is one last thing we need to do: make sure that the ‘posix.so‘ extension is loaded into PHP!  Open up your php.ini – for me, it’s located at /etc/php/php.ini. Head to your ‘Dynamic Extensions’ section, and make sure that

1	extension=posix.so

is uncommented/enabled.  If you don’t see it there, then add it!

Error Establishing a Database Connection

WordPress issue.  After migrating to Nginx, my WordPress MySQL database was totally hosed.  Running the fix that posted in that previous post didn’t help – I couldn’t figure out what was happening.

After digging around in MySQL, it almost seems like my WordPress MySQL user had dropped all of it’s privileges on the WordPress MySQL database.  I’m really not sure how this might have happened, and I don’t know enough about MySQL to be 100% sure of this, but this seems to be the case.

I tried a new fix, based on the WordPress Installation Instructions (specifically, the “Using the MySQL Client” section), and so far, everything seems great.

First, open up the MySQL shell:

$ su

# mysql -u root -p

Now, we want to operate on your WordPress MySQL table. If you don’t remember the name, you can have MySQL tell you all of the databases you have.  Once you figure out what it is, select it with the ‘use’ command:

mysql> show databases;

mysql> use wordpress;

Finally, it’s time to update your WordPress password, and re-grant privileges.  There are two lines of ‘privilege granting’ below.  The first is for your WordPress user on a certain host. For most people, “host” should just be “localhost”.  If you aren’t sure, look in your wordpress/wp-config.php file – it should be there under the HOST variable.  The next one uses the “%” wildcard in place of “host”.  I’m honestly not 100% sure if this is required, but my stuff works now, and it didn’t before, so take it for what you will.

mysql> UPDATE wp-users SET user_pass = MD5(‘password’) WHERE user_login = ‘login’;

mysql> GRANT ALL PRIVILEGES ON wordpress.* TO “login”@”host”;

mysql> GRANT ALL PRIVILEGES ON wordpress.* TO “login”@”%”;

Huzzah!  From here, you should be all set.  Again, I don’t know squat about MySQL (or any database software, really) – this fix worked for me.  If you have comments, suggestions, or other fixes, please share them below.

To get your Adobe PDF reader back, simply head to

about:plugins

in the address bar, and click ‘Enable’ under the Adobe plugin.   You should be all set.

ArchLinux VM Crashing at Startup

It turns out the fix for this is simple, but obnoxious: close any program (including Windows Explorer) that is using any part of a shared directory that the VM uses.  You could also just remove the shared directory from the VM, but then there isn’t much point in having the shared directory to begin with.

I’m really not all that sure how this bug made it into a release, but hopefully they patch it soon!