Rtl_fm Guide: The long lost documentation

rtlsdr
Kyle Keen has written up documentation on his Rtl_fm utility, which enhances RTL-SDR operation on older PCs.

Rtl_fm is a little utility I wrote for the RTL-SDR project. The program was made to fill a gap in software defined radio: all the computers weaker than a Pentium 4. Basically, an Atom processor processor does not have enough oomph to demodulate something as simple as narrow band FM using the standard tools. (Recently a high performance FM demodulator was released, Simple FM but it works only passably on newer Atoms.) So rtl_fm was written with one goal, efficiency, in mind.

Rtl_fm is one of the user-level packages which comes as part of the rtl-sdr codebase.

Visit KK Blog for the documentation.

YALEDD! 16×16 LED display

IMAG0669[1]

Andrew Rossignol has written an article detailing his YALEDD – 16×16 LED display project:

The class was instructed to choose a simple circuit such as an LED flasher or a simple sequential state machine composed of discrete logic, capture the schematic, layout the PCB and have it made by the end of the term.
I decided that it would be boring to design a simple state machine. I also thought it might be pretty cool to have an electronic gizmo of my own design to show off on my desk at work.

Ambient Backscatter – Wireless power and communication with no batteries

ambient_backscatter

Ambient Backscatter – Wireless power and communication with no batteries

Ambient Backscatter transforms existing wireless signals into both a source of power and a communication medium. It enables two battery-free devices to communicate by backscattering existing wireless signals. Backscatter communication is orders of magnitude more power-efficient than traditional radio communication. Further, since it leverages the ambient RF signals that are already around us, it does not require a dedicated power infrastructure as in RFID.

Via Hacked Gadgets.

Check out the video after the break.

Continue reading “Ambient Backscatter – Wireless power and communication with no batteries”

Arduino 28BYJ-48 stepperbot

stepperbot

Bajdi’s another robotic vehicle with 4 28BYJ-48 stepper motors:

The Arduino IDE comes with a stepper library, but I decided to write my own stepper code. For 4 stepper motors I would have needed 16 digital pins and then another 4 pins for the servos. Controlling a stepper motor is not that difficult. It’s just a matter of setting the pins high/low in the right sequence at the right time. I thought why not try and use a couple of 74HC595 shift registers to control the stepper motors? I have controlled 16 leds with 2 shift registers in the past so why not 4 stepper motors? I soldered 2 shift registers to a piece of perfboard and tested the board with some leds. That worked

Free PCB Sunday: Pick your PCB

xQFP50 plus65 Protoboard-W800

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 two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB.

You get unlimited free PCBs now – finish one and we’ll send you another!

Don’t forget there’s free PCBs three times every week:

Continue reading “Free PCB Sunday: Pick your PCB”

App note: VCO enables a hands-free car kit for cell phones

ap_vco_handsfree_car_kit

Locally broadcast your cell phone through FM band using MAX2606 from Maxim. App note can be found here.

This design idea presents an integrated IF voltage-controlled oscillator (VCO) that can retransmit the audio signal from a cell phone to the FM broadcast band. By placing the cell phone’s speaker near the microphone, the user can use the phone as a hands-free device while driving.

App note: Biasing and decoupling op amps in single supply applications

biasing_op_amp_single_supply

Op amps needs dual supply in order to get a full output swing from its input fed signal, here’s a good app note from Analog Devices on powering op amps using only a single supply.

Battery-powered op amp applications such as those
found in automotive and marine equipment have only a
single available power source. Other applications, such
as computers, may operate from the ac power lines but
still have only a single polarity power source, such as
5 V or 12 V dc. Therefore, it is often a practical necessity
to power op amp circuits from a single polarity supply.
But single supply operation does have its drawbacks: it
requires additional passive components in each stage
and, if not properly executed, can lead to serious instability problems.

App note: Power supply layout and EMI

pwr_supply_layout_and_EMI

Reduce EMI by determining large alternating currents carrying areas and making them compact, this minimizes radiation and spilling of unwanted signal to other part of your PCB. More of these methods are shown from Linear Technology’s app note.

PC-board layout determines the success or failure of every power supply project. It sets functional, electromagnetic interference (EMI), and thermal behavior. Switching power supply layout is not black magic, but is often overlooked
until it is too late in the design process. Fortunately physics
is on your side. Functional and EMI requirements must
be met, and in a world of trade-offs in power supply unit
layout, what is good for functional stability is good for
EMI. Good layout from first prototyping on does not add
to cost, but actually saves significant resources in EMI
filters, mechanical shielding, EMI test time and PC board
runs. This application note focuses primarily on nonisolated
topologies, but will examine some isolated topologies as
well. You will learn to make the optimum choices regarding
PC-board layout for solid power supply designs.

App note: Measuring temperature with PIC16F84A WDT

temperature_sensing_wdt

Here’s an app note from Microchip on how you can use the watch dog timer of an old trusty PIC16F84A as temperature sensor.

Almost all temperature sensor circuits use some form of discrete component (such as a thermistor or a solid-state sensor) to actually measure the environment?s temperature. It is left to the microcontroller to interpret the reading into a human-friendly form for the user?s benefit. It is possible, however, to design a digital thermometer without an external sensor, by using a temperature sensitive property of the microcontroller itself. This Application Note shows how to use the Watchdog Timer (WDT) of a PICmicro ® microcontroller for temperature measurement.

Decoding radio-controlled bus stop displays

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Oona Räisänen (a/k/a Windytan) is a self-taught signals and electronics hacker from Helsinki, Finland, who is fascinated by mysteries, codes and ciphers, and vintage tech. She’s previously written regarding the use of digital transmissions carried on FM broadcast subcarriers as a means of supplying data to digital information signs used at bus stops. Continue reading “Decoding radio-controlled bus stop displays”

Rapid development board for PIC12F series microcontrollers

PIC12FDEVBOARD3

Here’s Embedded Lab’s new development board for PIC12F series microcontrollers:

The 12F series of PIC microcontrollers are handy little 8-pin devices designed for small embedded applications that do not require too many I/O resources, and where small size is advantageous. These applications include a wide range of everyday products such as hair dryers, electric toothbrushes, rice cookers, vacuum cleaners, coffee makers, and blenders. Despite their small size, the PIC12F series microcontrollers offer many advanced features including wide operating voltage, internal programmable oscillator, 4 channels of 10-bit ADC, on-board EEPROM memory, on-chip voltage reference, multiple communication peripherals (UART, SPI, and I2C), PWM, and more. Today we are introducing a new development board (rapidPIC-08 V1.0) for easy and rapid prototyping of standalone applications using PIC12F microcontrollers.

Purpleheart ornamental clock

Photons

Wardy wrote a post on his blog detailing his ornamental clock build:

I wanted to use my new Adafruit Neopixel Ring to build an ornamental clock, using this interesting woodworking technique. Plus I figured that my milling machine might make this a feasible prospect.

Milling, in my very limited self-taught experience, is best done using a material that is of a consistent density. Wood, (again in my very limited self-taught experience) isn’t consistent in it’s density. Softwood especially. So I turned to the densest wood I could get my hands on and assumed that it would simply behave like a very soft version of aluminium. Here’s the aggravatingly cursory build log…

Free PCB coupon via Facebook to 2 random commenters

XT IDE disk controller v1b - Click Image to Close

Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. More PCBs via Twitter on Tuesday and the blog every Sunday.

Don’t forget there’s free PCBs three times every week:

Continue reading “Free PCB coupon via Facebook to 2 random commenters”

Week in (p)review November 29, 2013

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Here’s a summary of major developments over the last week. Free PCB Friday is coming up soon.

Coming up:

  • Free PCBs via Facebook on Friday
  • App notes on the weekend
  • Free PCB Sunday
  • Free PCBs via Twitter on Tuesday
  • Weekly roundup and preview every Friday

OSUS – Open source USB Stack test board (Master)

SAMSUNG

Here’s another cool project by Mats the OSUS Master board:

A long while ago I wrote about that I might make a series of boards for easier testing of the open USB stacks. Testing all different version of mcu’s and crystal speeds to make the right #defines and linker maps for the firmwares can be a bit tedious.

OSUS will make life a bit easier by removing most of the parts required on the boards to be tested down to a master board. The test-boards basically only need a decoupling cap two and a 14 pin 0.1″ pin header – that’s it.

Files available on Github.

Via the project log forum.

Constant current circuit for IR LEDs

IRsignaltraceRectifierDiodeIN4148
The crew from AnalysIR reports they have written up an article on constant current circuit for Infrared LEDs – similar to that in the USB IR Toy. They compare the various methods of driving IR LEDs, including a series resistor and a circuit driven by an NPN transistor, and how to design your circuit for maximum brightness.

For details visit the AnalysIR blog.

Via the contact form.

STM32F4xx libraries

STM32 F4 Series

mux writes:

I wrote a tutorial before on how to setup a toolchain and build the STM32F4xx standard peripheral drivers into one convenient library, since then, a few people have asked me about the library, so to make life easier, I downloaded the latest StdPeriph/CMSIS, in addition to a few other libraries that I might need later, and shared everything in one repository, which currently has the following libraries…

Digitstump’s Black Friday sale

2013-11-28_2221

Ihsan informs us of Digitstump’s Black Friday sale:

We are pleased to announce that Digistump.com will be offering some amazing deals for Black Friday thru Cyber Monday – while we can’t compete with the big stores, because we don’t have 2-3x mark-up like they do, we hope these deals will help you buy engaging, educational, electronic gifts for your loved ones, or allow you to get yourself some kits to build while you hide from your relatives during the holiday season.

Micro Python: Python for microcontrollers

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Torsten came across an interesting project on Kickstarter called Micro Python by Damien George.  He writes:

It has some very nice new design ideas as well as a totally new way of dealing with uC. I often do prototyping of a certain algorithm in python because it is very easy to debug and test. After that, I go an implement it in the uC-architecture of choice.
Just think of that you could directly use the Python code.

In addition it is a very nice read about the internals of scripting
languages and what need to be considered to run them on a small architecture like a uC. The founder seems very knowledgeable about pythons internals. He rewrote many internals to optimize it for a uC environment. He managed to speed up the execution by tenfold and brings python execution time almost as close as its C equivalents!
Nonetheless, you can execute almost arbitrary python 3 code.

Via contact form. Thanks Torsten!