N Bit Wonder

VoIP32 Progress

Ben — Fri, 16 Jul 2010 05:17:42 +0000

Over the last couple of weeks, I’ve spent some time working on the TCP/IP stack used by VoIP32 to handle all its network connections. It only recently gained the ability to properly manage a relatively large number of concurrent connections, limited by available RAM. The firmware is currently set to allow 10 simultaneous connections. The PIC32MX340F512H has 32kB of RAM, which should be enough to support some 25 simultaneous clients. The ~380kBps of available bandwidth is shared among all connections.

The total available bandwidth is a bit lower than expected, but is still nearly 60% higher than the available bandwidth on VoIP8. As I write this, I am downloading a file from VoIP32 at a sustained rate of 375kB/s. When compared with large commercial Web servers, this isn’t impressive at all; however, we must keep in mind that this server is running on an 80MHz processor with limited RAM instead of a quad-core Intel chip with gigabytes of memory.

Other tweaks added recently (but not yet fully debugged) are case corrections in filenames to support non-standard Microsoft extensions (this mostly works) and automatic TCP packet retransmission (this still needs some work).

The next steps planned are to start working on a Telnet UI for administrative purposes, a pushbutton-and-LCD-based local UI, and possibly integration with services like Pandora and Twitter.

Other things that I would eventually like to add include a bootloader for remote programming, a Unix-like Telnet or SSH interface, and the ability to execute small programs from the SD card.

End of the school year, and some news

Ben — Sat, 15 May 2010 22:17:08 +0000

First, let’s congratulate George. He has graduated from Purdue University as of this morning, so he is now qualified to go forth to solve the world’s engineering problems. Congrats, George!

With the end of the school year comes moving to new places, and as such, the 8-bit Web server has come out of storage. What’s different than last time is that it now has the LED array hooked up and playing the messages that Internet users send to it. To give it a try (and send stuff to the LED array), simply visit http://benlaskowski.is-a-geek.net:8000/.

As I will have a little more free time this summer, I intend to get the 32-bit VoIP board up and running. I have so far made it send dummy ARP packets over the network correctly. Complete implementations of TCP/IP and the like are a long way off, but hopefully everything will come together this summer.

Edit: VoIP32 now supports ARP and ICMP. Yes, these are small steps, but it shows that different buffers work properly and that I actually can correctly compute checksums in software. In preliminary testing, the board can echo 1kB of ping data in one millisecond. Not too shabby…

NBitWonder Tutorial: PWM Operating Theory

George — Fri, 19 Mar 2010 17:51:06 +0000

Tuorial Number 2 was posted today, covering Pulse Width Modulation (PWM) operating theory and the differences between hardware and software implementations. Check it out here!

NBitWonder’s First Tutorial: An Introduction to the mbed

George — Thu, 18 Mar 2010 21:40:54 +0000

The mbed is a prototyping platform that came out late last year. Featuring a cloud-based compiler, intuitive development environment, and powerful 32-bit ARM processor, the mbed is designed to help expedite prototyping of electronics concepts. With this in mind, the folks here at NBitWonder created a tutorial that serves as an introduction to the mbed platform. Check it out here.

Website Updates

George — Mon, 15 Mar 2010 16:14:58 +0000

We’ve been hard at work here at NBitWonder the last few days implementing some updates to the site, and work will undoubtedly continue throughout the course of the week. While this work goes on, you may consider checking out the new ‘Resources’ tab, which links to all sorts of interesting sites to help quench your thirst for electronics and making things in general.

Browse Science Over the Ages

George — Thu, 04 Mar 2010 22:06:30 +0000

via adafruit

Here at NBitWonder we try to keep the blog focused on electronics projects, but this was just too good to pass up. Popsci writes:

We’ve partnered with Google to offer our entire 137-year archive for free browsing. Each issue appears just as it did at its original time of publication, complete with period advertisements. It’s an amazing resource that beautifully encapsulates our ongoing fascination with the future, and science and technology’s incredible potential to improve our lives. We hope you enjoy it as much as we do.

So get to it! Check out the PopSci archives today! And if you find something cool, share it with us!

VoIP32 Plays Audio

Ben — Fri, 19 Feb 2010 04:31:31 +0000

The 32-bit VoIP board can, as of tonight, play media from a microSD card inserted into the onboard socket. This has the added bonus of demonstrating that the code segments for fragmented file handling, file name caching, SD card file searches, and cooperative multitasking all work as they should.

Right now, the handler for audio playback is the SD card filesystem reading layer. It’s specific to audio tasks, but a bit of rewriting should make it much more general so that every task needing SD card access will be able to use it.

This means it’s time to start working on the Ethernet capabilities of the server. This comes at a time when the semester is starting to pick up, so we’ll see how quickly this is accomplished.

CardPOV Progress

George — Wed, 17 Feb 2010 03:36:48 +0000

It’s been a little while since I posted the state of the CardPOV project, but after some trials and tribulations version 1 of the CardPOV device is finished. I went ahead and laid out a board in Eagle for the device, creating a much improved POV.

Particular improvements on the POV device over it’s protoboard predecessor include the migration from the 5V PIC18F2550 to the lower power 3.3V PIC18F25J50. This has allowed me to power the entire system off of a single CR2032 coin cell battery instead of bulkier AA batteries and also eliminates the need for a voltage regulator. All parts (except the leds, for the moment at least), have been switched to surface mount components, which has made the device considerably more compact. Finally, in the latest version of the software, multiple string support has been added. This feature allows the user to store multiple POV strings into the device memory and toggle between them using a pushbutton. The current code configuration allows for a maximum of 255 unique strings to be stored on device. A video of the device in action is included below.

More updates on the CardPOV device as they become available, so stay tuned!

32-bit VoIP Update

Ben — Tue, 16 Feb 2010 06:47:05 +0000

I’ve spent a few hours (okay, okay, more like 20 hours) over the last two weeks working on implementing SD card support in MIPS assembler. As of approximately 15 minutes ago, the code successfully implements some subset of the SD SPI protocol as well as FAT32.

Three unique features as compared to commercial implementations are long file name support, (mostly) unlimited nested sub-directory support, and FAT32 support. The sub-directory support is a direct consequence of the PIC32′s large RAM and stack mechanism, providing an easy way to implement context saves when changing directories. Long file name support makes it such that the firmware can break past the “8.3″ filename barrier, however (and this is a BIG however), this code will NOT be publicly released due to Microsoft’s restrictions on the algorithm the code uses to implement LFN support. TomTom has been taken to court over similar issues, and I’d rather cripple my code than go up against Microsoft in court. Lastly, FAT32 support enables support for large files and large SD cards (the firmware should support up to 4GB cards).

Still to come, hopefully in the next week or two:

Efficient SD card search algorithm
File system access layer for opening, reading, writing, and closing files
Media playback from SD card
Ethernet MAC/PHY initialization code
Begin work on IP stack

To round things out (and prove it works!!), here’s a screenshot of a terminal session with the board, showing the last few directory entries on the card and a debugging menu:

RGB Lightsaber Reliability Testing

George — Tue, 19 Jan 2010 22:42:16 +0000

The RGB Lightsaber prototype is nearing preparations for production. The board faithfully performs correctly under 4.5-5.5V, the voltage range one generally expects from 4 rechargeable NIMH batteries. Still, in order to verify that that claim is indeed the case, I performed a round of power tests today. The tests consisted of testing each of the single colors (red, green, and blue), followed by testing all of the 2 color combinations (red green, red blue, and blue green), and then a 3 color test (red green blue). A “test” consisted of turning up the selected color (or colors) all the way, and then leaving em on full bore for 10 minutes. In summary, the tests were very successful, the saber having passed all of them. Photos from the testing process found below.