Convert the Chumby serial port into two PWM outputs

Osman Eralp of Ozbots writes:

When I was building my latest Chumby-based robot, I didn’t need the serial port, but I did want PWM signals to control the robot’s wheel motors. Fortunately, the processor pins that are used for the serial (UART) TX and RX pins are multiplexed with PWM outputs. With the proper commands, you can tell the processor to output PWM signals instead of serial TX and RX.

His process involves four steps which may be accomplished through one of two methods: either running regutil (a command line utility), or adding C code to your robot program. When completed you will have changed the function of the serial TX and RX signals to PWM outputs.

Operational Amplifier howtos

The operational amplifier is one of the most useful analog ICs available, and one of the most daunting for beginners and experienced engineers.

Above is a diagram of an op-amp in a closed loop non inverting configuration. Probably the most used configuration. Lets assume this is an ideal amplifier. R1 is the input and R2 is the feedback. When R1 = R2 the circuit is in unity(meaning input = output).

To calculate output use the following formula.

– Closedloop1.jpg

R3 can be calculated by the following.

Closedloop2.jpg

learn more about operational amplifiers in the docs

Arduino based interactive punching bag

In an effort to enhance his workout, Lior Elazary designed an Arduino enhanced punching bag. The bag is outfitted with sensors made from aluminum foil and conductive foam, which are interfaced with the Arduino analog inputs via resistors. Bright LEDs are implanted in the bag near the sensors, and the Arduino flashes the LEDs in a programmed sequence. The user must strike the bag sequentially in the areas corresponding to the LED pattern.

The source code is provided, however since it was written using a makefile and vi editor you would need to make changes in order to use it with the Arduino IDE.

Handheld RF spectrum analyzer now available

Seeed has a new handheld RF Spectrum Analyzer designed by Arocholl:

As wireless communication devices grows in use everywhere, so it does the need to monitor, test and diagnose them.

RF Explorer is an extremely affordable Handheld Spectrum Analyzer designed from scratch to be a sort of Swiss Army Knife for the specific needs of ISM band digital communication.

FTDI VNC2 Vinculum II toolchain issues

Lots of people have been experimenting with the new FTDI Vinculum II USB host chip. We covered the Vinculum II board here and here.

It looks like the hardware and firmware are still a little rough. jpieper has documented a number of bugs, including issues with interrupts and the compiler. If you’re starting a new project with this chip you might be well served to check this errata before getting too far.

Via the forum.

Serial port only Bus Pirate v3b update

schazamp has another update on the serial port only Bus Pirate.

I have released BusPirate-v3b-FTDI-0.3, which has:

* room for a shrouded I/O header
* Sparkfun’s locking header rows
* more clearance around voltage regulators, for easier assembly
* improved label size and positioning

You can find the zip distribution here
Or check here for the source

Via the forum.

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.
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Parallax Propeller/WiiMote white board

In this project, Gareth from Let’s Make Robots demonstrates how to interface a Parallax Propeller with the WiiMote and LCD display to form a white board. Inspired by the work of Johnnie Chung Lee with the WiiMote, Gareth uses the Propeller chip programmed in the Spin language to process data and interface with the display. The key to the whole idea is a simple hacked WiiMote camera tracking an infrared blob of light produced by a light pen consisting of an LED, resistor, switch and 3.3V battery. We’d like to see the schematic and source code!

Via Hack a Day.

Arduino varies LCD contrast using PWM

We’ve seen a number of tutorials explaining the use of LCD displays with Arduino. In most the display contrast is varied by use of a potentionmeter. Here’s a tutorial from Hobbytronics which varies the contrast using PWM. A 100uF capacitor is connected between the PWM output and ground to smooth the signal. Using this technique allows you to code contrast changes into your sketch, such as allowing contrast to automatically vary based upon the value read from a LDR. Sample Arduino sketch included.

ITead Studio Colorduino preview

lincomatic wrote a review of ITead’s Colorduino, and also released an Arduino library that works with both the Colorduino and Itead’s Arduino RGB Matrix driver shield.

ITead Studio kindly sent me a Colorduino for beta testing. The Colorduino was inspired by SeeedStudio’s Rainbowduino LED Driver Platform. Its form factor is very similar to that of the Rainbowduino, and the layout of the connectors was intentionally designed to mimic the latter. Both boards are based on the ATmega368 MCU, and are Arduino compatible.

Thanks lincomatic! Via the contact form.

Logic Sniffer: 3.07 Demon core release

There’s a new one-stop shop for the Logic Sniffer at Gadget Factory, with Linux and Windows update packages containing the latest 3.07 releases:

OpenBench Logic Sniffer Version 3.07 is now available for download at the new Logic Sniffer information portal.

For more information take a look at the Release Notes.

This release was generated with the new cross platform build system located at Github. There are full and partial releases for both Windows and Linux. Mac OS X is soon to follow.

Please note that the information portal is still a work in progress. If you have any ideas or suggestions please respond here or drop by the Gadget Factory IRC channel.

Via the forum.

Get a Logic Sniffer for $50, with free worldwide shipping.

GSM SIM emulator using PIC Microcontroller

Here’s a project from EHobbyProjects which demonstrates their hack for emulating a GSM SIM card using a microcontroller, EEPROM and SIM card adapter. Their instructions include reading the IMSI and KI data from the original SIM, and then using their Configurator program and hex programming files in conjunction with a PIC16F877 and 24C64 EEPROM to modify and load the desired SIM data into the PIC. Once programmed, the PIC/EEPROM SIM emulation device is connected to the GSM phone via a SIM card adapter.

This is not a hack we tested, and is presented for educational purposes only.

Here’s a tutorial on using the Bus Pirate to interface with a SLE4442 card, which may give some ideas on reading data from the original SIM card.

Seeed Studio Arduino ProtoShield kit remixed v1.0

Seeed Studio has their Arduino ProtoShield kit remixed V1.0 selling today for $12.90. The shield kit features 100mil grid, full pinout of the Arduino, USB B type connector, free drill hole matrix of 32/50/80mil, breadboard style strip, UART and I2C pinout sets, 5V/GND/3V3 power rails, a free button as well as reset button pinout, Pin13 LED pinout, power jack pinout, potentiometer, switch, LEDs and resistors and all necessary headers.

Check out the Logic Sniffer, Bus Pirate and full line of Dangerous Prototypes products also available at Seeed Studio.

Free PCB Sunday: Bus Blaster v1

We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service.

This week we’re giving away only one PCB for the new Bus Blaster v1, it’s all we have left. Read about the design on the wiki.

Bus Blaster v1 is sold out, sorry. More Bus Blasters will be available in about a month.
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Week in (p)review: March 06, 2011

Don’t forget to share your current project in the comments or the forum. This week our favorite project gets a free SOIC protoboard.

Here’s a summary of major developments over the last week:

This week we’ll have new stuff in the Seeed shop, and continue evaluating some new ideas:

  • New v2 dangerous protoboards
  • Can we fit a simple logic analyzer into a 72 macrocell CPLD?  Our Verilog adventure continues
  • We’re looking into the May Maker Faire

What are you hacking this week?

Openstack: open source, open standards cloud

Openstack is celebrating its six month anniversary! OpenStack is a collection of open source technologies delivering a massively scalable cloud operating system. OpenStack is currently developing two interrelated projects: OpenStack Compute and OpenStack Object Storage.

OpenStack Compute is the underlying cloud computing fabric controller for the OpenStack cloud. This means that all activities within the OpenStack cloud (such as starting and stopping virtual machines) are handled by this product. In effect, OpenStack Compute is the “operating system” for the OpenStack cloud and manages all resources, networking, authorization, and scalability needs for the cloud. OpenStack Object Storage is software for creating redundant, scalable object storage using clusters of commodity servers to store terabytes or even petabytes of data.

Openstack is backed by Rackspace, NASA, Dell, Citrix, Cisco, Canonical and over 50 other organizations. All of the code for OpenStack is freely available under the Apache 2.0 license. Anyone can run it, build on it, or submit changes back to the project

QUISK software defined radio

QUISK is open source software defined radio (SDR) platform by James Ahlstrom. QUISK can interface with certain radio receivers or amateur radio transceivers, and essentially takes over control of the rig’s operation including changing mode, frequency, transmit/receive switching, demodulation, etc. It’s written in Python and C, and all source is included.

QUISK runs under Linux using ALSA sound drivers or PortAudio. As a receiver it can use the SDR-IQ by RfSpace as a sample source. There are several decimation rates available. The QUISK receiver will read the sample data, tune it, filter it, demodulate it, and send the audio to the sound card for output to external headphones or speakers. It can also use your soundcard as a sample source. You supply a complex (I/Q) mixer to convert radio spectrum to a low IF, and send that IF to the left and right inputs of the sound card in your computer. The demodulated audio goes to the same soundcard for output.
QUICK can also control SoftRock hardware for both receive and transmit.

To install QUISK, download it here (search for QUISK). Then read the documentation and the help file for further instructions.

While it lacks many of the more complex functions of the GNU Radio/USRP SDRs, QUISK gives the hobbyist a relatively inexpensive, open source way to experiment with software defined radio.

App note: High-quality white noise generator

A white noise circuit could be interesting part of a modular synthesizer. This design has no 1/f component, meaning no annoying repeating sounds in the white noise.

In this noise-generator circuit, the amplifier (MAX4238) has no 1/f component in its input voltage noise. It amplifies its own input-voltage noise with a feedback network made with low-value resistors, to avoid adding noticeable 1/f noise either from the resistors or from the amplifier’s input noise current.

Thanks rsdio!

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