As you may know, one of the projects in the pipeline here at NBitWonder is a software-defined radio receiver, loosely modeled after Jeri Ellsworth’s receiver published earlier this year.  As of this past weekend, NBW-SDR (as we call the project) is operational!

The video features a live reception of WWV, one of the United States’ atomic clock stations (much more information here).  The station is located near Fort Collins, Colorado, some 2000 miles from the receiver’s location in Virginia.

There is much more work to be done on the software, as you can tell from watching the video.  For instance, only AM reception is implemented right now.  The signal processing functions still need some work, and more appropriate gains should be chosen for the entire signal chain.  Still, it is rewarding and reassuring to see the project working at some level.

Be sure to watch the github repository and the forum for much more information as project development proceeds.

I took a couple of hours tonight to put together the Software Defined Radio PCB, as the parts arrived a couple of nights ago.  Software development has already started — check out the git repository for the progress so far.  Be sure to watch the project in the forum to stay abreast of project progress!

The latest revision of our Software Defined Radio project PCBs arrived the other day.  While we wait for parts to arrive, be sure to check out the progress over in the forum!

Over in the forum, we’re designing a software-defined radio modeled after Jeri Ellsworth’s Hackaday post from earlier in the summer.  We ordered PCBs for the first revision perhaps a bit too hastily, as some forum members with valuable experience in the area found a number of shortcomings in our design.  Those have been corrected (we hope!) with this latest round of updates.

Changes that have been made include moving to a better oscillator module (wider frequency range, better stability, less phase noise) and to an external 24-bit ADC (for higher dynamic range).  We have a few boards of the old design already fabbed, but things like work and school keep getting in the way of building up a prototype or two to start coding.

Check out the schematic and layout over on github (or just grab the latest NBitWonder Eagle Library update), and let us know what you think in the forum!  We might not always respond right away, but we value your input.

(Via IEEE Spectrum)

Do you want to learn more about Artificial Intelligence?  From Stanford?  …for free?!  If so, then today is your lucky day!

IEEE Spectrum, a publication of the Institute of Electrical and Electronics Engineers, reports that Stanford will let you do just that this fall.  Two 75-minute lectures per week will be videotaped and split up into 15-minute chunks for easy streaming.  Three days into registration, there are over 10,000 students signed up.

Check out the original article for the full story, or head over to the class website and sign up!

After much time spent writing code today, the lwIP stack is functional at some minimal level.  The board responds to ARP and ICMP (“ping”) requests.  As you can see in the screenshot above, 1280-byte packets are echoed in an average of 0.924 milliseconds.  As a point of comparison, the original VoIP32 hardware achieves a round-trip time of 1.47 milliseconds for the same packet size, and VoIP8, lacking sufficient memory for large packet sizes, weighs in at 6.27 milliseconds for 1024-byte packets.  This gives a (very) rough idea of the speeds at which each device can interface with the network.

There is still a lot of work to do to finish this project up.  To add in various servers, applications that interface to the lwIP stack will have to be written.  We will then be in need of an open-source USB stack and some sort of audio library for streaming media playback.  The code so far can be found in the github repository for this project.

After the tragic and unexplained death of VoIP32v2, a few changes were made to the PCB and another attempt was made to bring this project into the land of the living.

So far, I am pleased to report success!

As I write this, an interrupt-driven LCD driver is in place, the FAT12/16/32 file system library works splendidly, and the microcontroller is able to program the CPLD with a bitstream it pulls from the SD card.  The TCP/IP stack compiles into the project, though no attempt has yet been made to run its code.

I hope to write the low-level Ethernet functions soon, bringing network connectivity to the board.  Until then, be sure to check out the github repository for progress on the project.

As we prepare for Maker Faire North Carolina in a few short weeks, much project work has been happening here at NBitWonder.

• After the tragic death of VoIP32v2, a number of small hardware changes were made and a new PCB ordered. With luck, it will arrive in time to populate before the trip to North Carolina.
• A number of small changes were made to component values on the Class-D Amplifier to improve response at low frequencies and to potentially boost power output.
• Testing continues on the DC motor driver project.
• The very first NBitWonder T-shirt order has been placed.  Watch for the stylish fashion accessory to appear in a few weeks!

Every semester, a new batch of Purdue electrical and computer engineers work their way through ECE477, a project-based senior design course. As the NBitWonder staff are Purdue ECE alums ourselves, we have a strong connection to Purdue and its ECE program. Without further ado, here are the senior design projects from ECE477 this semester.

Quick links:
Team1 Team2 Team3 Team4 Team5 Team6 Team7 Team8 Team9 Team10 Team11 Team12 Team13 Team14 Team15
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The single-supply bridged version of the Class-D amplifier has been assembled, and I am most pleased to report that it works beautifully!

Input side of the amp

Output side of the amp

For those new to the project, a Class-D amplifier is a highly efficient amplifier that operates its output devices as switches instead of as variable resistors.  We posted a highly experimental version of this project last November, and it met with a surprising amount of positive feedback from the DIY community.  Therefore, we developed it as a formal project.

The amplifier has been converted into a single-supply version, which removes quite a bit of complexity from its power supply.  The ideal power supply used to be a custom-built bipolar supply capable of high currents, but now, an old laptop power brick that supplies 20V at a few amps is perfect.

A short demonstration video follows.  For more technical information, be sure to check out the github repository that contains a wealth of information on the development of this project.

Still remaining:  packaging the project.  I wanted to verify that everything worked before taking the time to stuff everything into a box.