I was recently reading an article on signal processing and embedded systems (Linux Magazine France n°149, p32-50, sorry, nice magazine browsing with page flipping, but in French only!). Stated shortly, the article first provides some concepts on Fourier analysis before implementing a fixed point FFT on an STM32 microcontroller and applying it to a continuous Wave (CW) RADAR system.
This article is making reference to Maxim's AN3722 "Developing FFT Applications with Low-Power Microcontrollers" that turned very difficult to find, as Maxim apparently wiped it from its servers!
After some time googling around for it, I eventually found it as a 2005 design article in EETimes, later included in Maxim's EngineeringJournal #57 pp. 9-13. There is a corresponding "3722Firmware.zip" file that is also quite difficult to locate, but is eventually still hidden somewhere at Maxim's here!
Originally written for the MAXQ CPU, it can be ported easily to other CPUs, as it is written in pure C.
This is really great stuff if you want to do real-time FFT on a microcontroller.
On the same subject, a recent (October 2011) Application Note from NXP (AN11115 with source code) is using similar technique to perform a quite impressive real-time FFT on audio over an USB device link on a small Cortex-M0 LPC11U14 CPU: [attachment=0]
I found an easy way to create a 360° panorama/swivel (à la 3D Warehouse preview).
Just download the Google (now Trimble) SketchUp Web Exporter (Beta) plugin.
Run the installer and specify your Sketchup install directory (do not put the "/Plugins" at the end of the path, otherwise, you will get nested "Plugins/Plugins" directories).
Make sure everything is OK by looking into the Sketchup "Plugins" directory: you should get both a "swivelButtonPlugin.rb" script and a "swivelButtonPlugin" subdir.
Now launch Sketchup, you should get a small floating tool window with this icon: [attachment=0] Dock this tool into a convenient menu bar, open a model and click on the tool button. A dialog will pop up, allowing you to change the image size, the resolution in degrees and the output directory location:
[attachment=1] This tool will create in the given directory a collection of JPEG pictures and an HTML file containing the JavaScript code to animate the panorama, as well as a ZIP file containing the above files for convenient deployment on a website.
Getting a BP is always a good idea, it is very useful for experimenting!
But if you want a more permanent setup where you don't want to monpolize a BP, you can get a handful of cheap Nokia CA-42 USB data cables from eBay for $1.34/ea. + shipping.
The PCB is molded into plastic goo on the USB plug side. You don't have to, but if you remove it, here is what you will find: [attachment=1][attachment=0]
These are ultra-simple Prolific PL-2303-based converters, just cut on the other side the Nokia funky connector, here is the pinout:
Black =>GND
Red => TXD (out from PC)
White => RXD (in to PC)
Here are the drivers (you will get an error, just use "guest"/"guest" as login/password).
I'm really thinking of buying the MK802 for $65, and then picking up an APC when it becomes available.[/quote] Mine's already on the way from AliExpress :-) I will be using it primarily as an addition to my set top box. But I'm waiting for the VIA APC to release. That looks more hacker-type.[/quote] Sorry, It looks like I missed that one!
[quote author="IPenguin"]... and the MK802 has NO Ethernet and NO (accessible) GPIOs[/quote] Yes, but it has Wifi, so Ethernet is not so much important. Of course, no GPIO given the small size... I was planning to hook up an USB-enabled microcontroller to expand GPIOs!
[quote author="IPenguin"]The MK802 has been around for a few month.[/quote] From the video linked above featuring the developer, the first prototypes were finished in May! Preorders started June 7th. So I grant you one month, not a few ;)
[quote author="IPenguin"]Even Linux ports are available by now. [/quote] ... Since July 4th, so it's kinda hot from the oven!
To get an idea about the USBug cost, the total amount for my initial 4 part kits order from Digi-Key was 75.33€, shipped to my place (EEC). But it is kinda lottery with the customs, they may charge you additional 10~20€, depending on agent :)
Comparing this price to the other equivalent finished boards, it's not that bad:
Of course, you can find other cheaper/better board, like the RPi, the OLinuXino-Micro or the Chumby Hacker boards (or a few other Chinese boards from eBay, like the FriendlyARM), but if you want to learn small ARM embedded microcontroller CPU programming on bare metal (no Linux here!) with modern tools as well as SMT soldering, the USBug may be a project to consider.
Yeah, but I am sick of reading headlines describing how to make a cardboard case or a filmsy case for the RPi...
In the said video, Linus is stating that "I don't believe in a world where every child should be taught to program" and "not everyone has the ability to be a programmer, but if 1% of all Raspberry P.I. help these persons who has this ability to program to realize: Hey this is cool!, then great".
The perverse thing I foresee is that having almost disposable powerful computers, people will miss the uttermost important goal of efficiency, which makes a hack beautiful. As an example, you see more and more projects that use an RPi for "blinky" project, rather than trying to do the same thing with more adequate small microcontrollers. And in this sense, the RPi is distracting people from reality.
That said, the RPi is an interesting machine, despite its flaws: it is too slow for a desktop computer, has serious USB bugs and an inefficient linear power supply (not counting for the closed GPU/datasheet already mentioned above).
I agree with both arhi and ipenguin for the reason that you can roll your own iMX233- and A13-OLinuXino board if you wish, but no way for the RPi...
That being said, there is so much hype on the RPi... They are drawing so much attention on the Net among hackers that there is barely enough space left for other projects to exist.
As for me, I am ready to order asap the first free-GPU-based board around!
I have a few bare rev. A boards left (10 out of the initial 20 batch from SeeedStudio), so if someone is interested, please send me a PM.
I have been asked for part kits, which I don't supply at the moment. Unfortunately, there is not enough interest (yet!) to start a fulfillment @ SeedStudio Propagate service, as they charge $500 for setup fee and service, plus you have to advance the parts for 100 kits min...
However, this may be a good idea to start grouping part orders, as we can save on individual distributor shipping fees this way.
I put both a Digi-Key and Farnell basket on Github, so you may have an idea of how much it will cost if you order one by yourself, and how much we can save by grouping.
Let me know by PM if you are interested in such a grouped part order.
Still, the A13 datasheet isn't complete: for each IP block, it only gives the corresponding pinout, no details on the registers. Nothing on GPU either...
I think when RPi or Olimex is designing a board with "community" in mind, they shouldn't use a part that has some kind of restricted access to specification.
The point is: I don't care about getting the cheapest or most powerful board around, I want it to be completely FREE (as in "speech"), so as triden above, I could just build it myself if I want to. THIS IS where the hacker fun (and true knowledge!) is.
