Python: Los Alamos Memo 10,742

Tonight at our local PYPTUG meeting (local Python User Group), I'll do a lightning talk on Los Alamos Memo 10.742.

I'll post the code and everything later and it will probably be of interest to anybody learning Python. I cant say much more than this (and, no, it's not a classified memo).

François
@f_dion

Wanted: speaker for PyCon Brython talk

Anybody going to PyCon 2013 and is available to give a lightning talk? Since there was no way for me to go this year due to scheduling conflict, I'm looking for someone to give a lightning talk on Brython.


www.brython.info

Contact me if you are interested in doing it, as I'll be doing a major revamp of the documentation in English in the next few days. The French documentation is quite a bit more up to date.

François
@f_dion

Your Python-Fu is Strong

PYPTUG

This coming monday, I'll be talking about Python-Fu, or "The Gimp: how to write a plugin in 10 minutes" at the next PYPTUG meeting:

PYPTUG meeting, Monday February 25th @ 5:30pm
Wake Forest University, Manchester 241

Graphical Apps Scripting

The Gimp is not the only graphical package to have support for Python. Blender, Dia, Scribus and Maya are a few of them. I will probably cover a few of those in the future.

François
@f_dion

Python in Europe

From:

Python trademark at risk in Europe

"For anyone who works in a company that has an office in a EU Community member state, we need your help."

So if you work for a company who uses Python, in Europe, do follow the link above and read up about how a company is trying to hijack the Python name, and what you can do to help.

François
@f_dion

Minecraft Pi Edition available

The RaspberryPi edition download

minecraft-pi-0.1.1.tar.gz

The install

fdion@raspberrypi ~ $ gunzip minecraft-pi-0.1.1.tar.gz
fdion@raspberrypi ~ $ tar -xvf minecraft-pi-0.1.1.tar

More detail

Mojang.com
pi.minecraft.net

Python

So, before we get started in writing some python (such as the code I put here: minecraft python ), let's check out block.py in the mcpi/api/python/mcpi directory. It contains the types of materials that can be used:

AIR                 = Block(0)
STONE               = Block(1)
GRASS               = Block(2)
DIRT                = Block(3)
COBBLESTONE         = Block(4)
WOOD_PLANKS         = Block(5)
SAPLING             = Block(6)
BEDROCK             = Block(7)
WATER_FLOWING       = Block(8)
WATER               = WATER_FLOWING
WATER_STATIONARY    = Block(9)
LAVA_FLOWING        = Block(10)
LAVA                = LAVA_FLOWING
LAVA_STATIONARY     = Block(11)
SAND                = Block(12)
GRAVEL              = Block(13)
GOLD_ORE            = Block(14)
IRON_ORE            = Block(15)
COAL_ORE            = Block(16)
WOOD                = Block(17)
LEAVES              = Block(18)
GLASS               = Block(20)
LAPIS_LAZULI_ORE    = Block(21)
LAPIS_LAZULI_BLOCK  = Block(22)
SANDSTONE           = Block(24)
BED                 = Block(26)
COBWEB              = Block(30)
GRASS_TALL          = Block(31)
WOOL                = Block(35)
FLOWER_YELLOW       = Block(37)
FLOWER_CYAN         = Block(38)
MUSHROOM_BROWN      = Block(39)
MUSHROOM_RED        = Block(40)
GOLD_BLOCK          = Block(41)
IRON_BLOCK          = Block(42)
STONE_SLAB_DOUBLE   = Block(43)
STONE_SLAB          = Block(44)
BRICK_BLOCK         = Block(45)
TNT                 = Block(46)
BOOKSHELF           = Block(47)
MOSS_STONE          = Block(48)
OBSIDIAN            = Block(49)
TORCH               = Block(50)
FIRE                = Block(51)
STAIRS_WOOD         = Block(53)
CHEST               = Block(54)
DIAMOND_ORE         = Block(56)
DIAMOND_BLOCK       = Block(57)
CRAFTING_TABLE      = Block(58)
FARMLAND            = Block(60)
FURNACE_INACTIVE    = Block(61)
FURNACE_ACTIVE      = Block(62)
DOOR_WOOD           = Block(64)
LADDER              = Block(65)
STAIRS_COBBLESTONE  = Block(67)
DOOR_IRON           = Block(71)
REDSTONE_ORE        = Block(73)
SNOW                = Block(78)
ICE                 = Block(79)
SNOW_BLOCK          = Block(80)
CACTUS              = Block(81)
CLAY                = Block(82)
SUGAR_CANE          = Block(83)
FENCE               = Block(85)
GLOWSTONE_BLOCK     = Block(89)
BEDROCK_INVISIBLE   = Block(95)
STONE_BRICK         = Block(98)
GLASS_PANE          = Block(102)
MELON               = Block(103)
FENCE_GATE          = Block(107)
GLOWING_OBSIDIAN    = Block(246)
NETHER_REACTOR_CORE = Block(247)

That's a lot. So, next post I'll try to build something using Python with all the materials, to get a feel for what they are.

François
@f_dion

Audio numerique sur RaspberryPi

Audiophile

Pour que le Raspberry Pi coute le moins possible, certaines décisions on du être prise. Par exemple, il n'y a pas de CODEC analogique - numérique. De sorte que l'audio se joue par soit:

1) le port HDMI - audio numérique passée directement au téléviseur ou a l'ampli intégré avec décodeur DTS, dolby digital, master audio etc... Si on utilise le Raspberry Pi comme serveur de media, c'est parfait. Mais si on ne peut utiliser le port HDMI?

2) le port 3.5mm analogique - l'audio est générée par PWM (Pulse Width Modulation). Avec une fréquence suffisamment élevée, on peut arriver a 16 bit de résolution, comme les convertisseurs plus conventionnels. Dans le cas du Raspberry Pi toutefois, la résolution est un peu moindre. En plus, il y a un problème avec le pilote ALSA, de sorte que le son n'est pas vraiment... a la hauteur.

USB

Tout n'est pas perdu. En effet, on peut se procurer une carte son sur USB:
Mini PCM2704 USB sur ebay (A noter que le prix est a la hausse, de $4.00 par rapport a ce que j'ai payé ...).

C'est géré par le Raspberry Pi: 

$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp.
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 001 Device 004: ID 08bb:2704 Texas Instruments Japan

Et ça donne une sortie analogique 3.5mm de qualité (super sur casque d’écoute), une sortie SPDIF rca numérique et une TOSLink optique numérique.

de USB a SPDIF, TOSLink et 3.5mm analogique

Illusion d'optique

Dans mon cas, je saute le DAC. J'utilise la carte son comme interface numérique optique, qui se relie a un processeur de son numérique Technics SH-AC500D (qui lui se branche a un ampli):

Le processeur de son est sur le dessus

La lumiere au bout ... de la fibre

On branche la fibre sur un des ports TOSlinks

Le soft

mpg123, aplay et d'autres lecteurs audio qui utilisent ALSA vont fonctionner avec la carte, mais il faut effectuer un changement a un fichier de configuration:

$ sudo vi /etc/modprobe.d/alsa-base.conf

et sur la derniere ligne, on change le -2 par un 1:

options snd-usb-audio index=-2
devient
options snd-usb-audio index=0 nrpacks=1
et on reboot.

François
@f_dion

sudo ./laserpulse.py

Tron, Laser, Lissajous, RaspberryPi

Am I throwing together random words for titles now, in a weird captcha induced moment? No,  just condensing my interest in lasers in a few words.

You might have seen the laser digitizer in Tron: Legacy

However, in my case, what triggered my interest in laser, was the original Tron laser digitizer

A few years later, I had the chance to play with a good old HeNe red laser, pumping a mighty 5mW (well, in the 80s, it was impressive) in the college lab. One of the things I did with it was to draw Lissajous figures (or curves) on a wall (a large wall outside, at night - even cooler), using two little speakers and mirrors I had brought (the lab was set up to only do prism and mirror experiments).

Googling, I see a nearby school (Appalachian State) has one such kit in their physics dept:
http://www1.appstate.edu/dept/physics/demos2/oscillations/3a80_40.html

Anyway, fun stuff, making math and physics a lot more interesting...

Electronica

There was the artistic connection that also further fueled my interest in lasers. There is a lot to talk about here, since I've composed and performed electronic music for many years (still write some) and hosted a radio show for about 10 years etc, so that'll be for another time.

I will bring up one point right now though: you cant talk about lasers in music shows, without mentioning Jean Michel Jarre.

Jean Michel Jarre, Houston TX 1986

From his incredible live outdoor shows with lasers, lights and fireworks (one, a tribute to oceanographer Cousteau, had an attendance of over 2 million people in France in 1990) to his laser harp. Jarre without lasers wouldn't be the same.

On the road

The Raspberry Pi has a lot of appeal by itself, but I figured that it would probably be a good idea to add a laser in the mix. Since I had a presentation at PyCarolinas, I figured I'd write a script with Python (laserpulse.py, hence the title of this article) and build a little rig to project interesting patterns on the wall behind me.

My 50mW laser rig (also 500mW for day use)

The code for the pulsing is basically what is found in the RPI.GPIO dot dash article, and for the motor, in the 2bit H bridge article and PWM article.

So, using a laser in presentations, does it work? Well, at PyCarolinas, I got a lot of feedback on this, both during the presentation, after the presentation and even during other talks (heard during another talk "so we've learned today that lasers are cool")

In the audience: "I just want to say that this is the coolest command, ever."

On twitter:

Calvin Spealman @ironfroggy

sudo laserpulse.py with actual lasers! #pycarolinas

08:45 PM - 21 Oct 12

And so on and so forth. The conclusion is this: Science needs some showmanship. But please, be careful when playing with lasers!

Video

So I'll leave you with a video of my little rig above controlled by the Raspberry Pi, going to the music of a very British band, doing a cover of the theme of a very British TV show. Very apropos, since the Raspberry Pi is a very British computer, afterall.





Youtube video (Music by Orbital, Doctor? live at BBC)

[edit] I fixed the youtube link



François
@f_dion