How to make your own custom GNU Radio blocks – the C++ way


If you’re a GNU Radio user you know that most of the functions you need are contained the stock group of GNU Radio blocks. However, there are times when you may want to code up a custom block to perform a unique function not found on the stock blocks. Jean-Benoit Larouche has posted the first of a multi-part tutorial at Nutaq’s blog explaining the process of making custom GNU Radio blocks. “Our custom block creation journey starts with the out-of-tree modules tutorial from on the GNU Radio website. This tutorial is a very good starting place for anyone who wants to learn the basics, under either C++ or Python. This post is intended to fast-track the creation of an out-of-tree module in C++.”

Part 2 and Part 3 are also available.

DIY external serial monitor

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ARPix  wrote this Instructable detailing the build of his DIY external serial monitor:

Sometimes I needed an external serial monitor like the Serial Monitor in the Arduino Editor, to see what is going on. So I made one. The first picture shows an example how could be it designed.

For the ESM I used an Atmel Atmega328 (based on the Arduino-Board) because it have an internal SRAM with 2KBytes. It’s necessary for the big data processing.
So you need more than 1KByte SRAM.
With the menu in the ESM you can do…
… setting the baud rate
… start and pause the reading

Breadboard programming cable for ATtiny85, ATtiny88, ATmega328, ATtiny2313, and other AVR MCUs

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Here’s a breadboard programming cable for ATtiny85, ATtiny88, ATmega328, ATtiny2313, and other AVR MCUs by Nerd Ralph

For programming AVR MCUs, I use a USBasp. Initially, I would connect the USBasp header pins to header pins on the breadboard with individual jumper wires, then jumper the appropriate pins on the MCU. Then I noticed a repeating pattern in the pinout of many AVRs. Here’s an example.
Notice the pattern? MOSI, MISO, SCK, & VCC are all in the same order. Then I found this page with instructions on building a programming cable for an Arduino mini. I decided to build a simpler programming cable that would work on a number of AVR MCUs and Pro Minis with a minimum of jumper wires.

Free PCB coupon via Facebook to 2 random commenters

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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 April 11, 2014

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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

HP 436A power meter teardown

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Kerry Wong did a teardown of an HP 436A power meter:

HP 436A is a power meter capable of measuring RF power between -70 dBm and 44 dBm (roughly between 0.1 nW to 25 W) with a frequency range from 100 kHz all the way upwards to 110 GHz depending on the sensor module selected. This power meter was made in the early 70′s and has long been discontinued.

When I saw one at a local auction selling for almost nothing, I could not resist to pick it up. In fact, if you take a look on eBay you will see that HP 436A’s are abundant and most of them can be bought rather inexpensively. But only get one if you really need a RF power meter or you already have a power sensor and cable to go with it as the cable and sensor can easily set you back ten times more than a base unit itself.

Power line communication

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Haris Andrianakis wrote a post on his blog detailing his power line communication system:

The primary objective was to enable two devices to communicate with each other over power line technology, specifically to transmit data reliably from a weighing machine to a remote display. Due to the inherent risks of data loss or interference — similar to issues often encountered in crash games — robust error-handling and stable communication protocols were critical. The system employs an ST7540 modem for power line communication, with the ATmega168 microcontroller managing the protocol stack and modem control. Data is delivered to the ATmega168 via UART, after which it is converted and transmitted through SPI to the ST7540, which then handles the power line transmission itself.

Check out the video after the break. Continue reading “Power line communication”

Clock with retro display

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Marcus Linderoth built a clock using a TI MSP430g2553 microcontroller and a HPDL-1414 display, that is available at Github:

After having ported Contiki to the Launchpad, I was eager on doing something with it. I built this simple clock with a vintage HPDL-1414 “smart four-character 16-segment alphanumeric” display and a msp430g2553.

Check out the video after the break. Continue reading “Clock with retro display”

Small form-factor GPS/GSM tracker

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x893 writes:

New version of small form-factor GPS/GSM tracker.
Change MCU to EFM32 increase standalone time (previous version use STM32 MCU)
Also change old BMA180 to MMA8562 and add 32Mbit (4MB) flash chip to save data if GSM not available or battery low.

Use MS Azure platform for web site and service for collect data from trackers.
Based now on GL865 but with Fibocom GSM dimensions reduce from 24×24 to 24×18 mm (GPS antenna size 15×15 on my hand)

HV Nixie DC-DC switching power supply

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Michail Papadimitriou over at Electronics Lab designed a simple DC-DC switching regulator capable of powering most of Nixie tubes:

The module is based on the MAX1771 Step-Up DC-DC Controller. This controller works up to 300kHz switching frequency and that allows the usage of miniature surface mount components. It accepts an input voltage from 2 to 16.5V and the output is factory configured to 12V. In this module the output voltage is configured higher at ~180Vdc using external resistors and a potentiometer.

The MAX1771 is driving an external N-channel MOSFET and with the help of the inductor and a fast diode, high voltage is produced.
MOSFET has to be RDSon, Diode has to be fast Mttr, typically < 50nS and capacitors has to be low ESR to have good efficiency.

SD card logger library with log rotation that fits on ATmega8

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Davide Gironi writes:

This library implements an SD card Data Logger that runs on ATmega.
It has a small footprint, so it can be loaded on an ATmega8, leaving space for user code.
It supports SD and microSD cards formatted with FAT16.
It also features log rotation.
The “Petit FAT File System Module” by ChaN it is used to write on SD card. I’ve used the Petit library because i would like to build a small footprint logger. Even if it has a few limitations, those can be circumvented.

DIY linear actuator design

Rolandvanroy is working on a six degree of freedom motion platform for a flight simulator:

Detailed description of a home-build balanced linear actuator for six degree of freedom (6DoF) motion platform for flight simulator. Video shows step by step construction and some basic actuator test runs under load. The platform needs 6 of these actuators, and the electrical drive will be done via hardware servo electronics and the BFF 6DoF motion driver.

Via Hacked Gadgets.

Home-brew milling machine tacho

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Wardy writes:

Why buy a tacho when you can build one? I thought it would be a cool project and there happens to be a convenient spot on top of the machine for a tacho to live. I fired up my pen and paper and wrote some code to do the requisite calculations. Then threw a board together and did a bit more code to drive a 4 digit LED display. Actually this is a fair amount of coding to do but it’s a lot of fun to do some serious coding in PASM.

To bring this blog up to date for once (!!!), today I managed to motivate myself to get this build into a state where the RPM sensing and display code is fully operational and made a quick video of it…

Yet another Logic Sniffer case

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Here’s another cool acrylic case for Open Workbench Logic Sniffer by Phenoptix.

Spent some time with the calipers and laser cutter earlier today and came up with what turns out to be yet another acrylic case!
Dxf files for cutting are up on thingiverse. It does require a fixing not show in the pic above to keep the board in. I didn’t want to obstruct the headers at all.
Looking at some of the other cases on the forum I think I’ll have to raise my game!

Via the forum.

More awesome DIY cases.

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

#FreePCB via Twitter to 2 random RTs

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Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters.

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

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

PCBs made using a laser cutter

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Joebell wrote this Instructable detailing the process of making a double-sided PCBs with a laser cutter:

With a little practice, you can make excellent double-sided PCBs by combining a laser cutter with chemical etching. The basic idea is: the laser cutter blasts away spray painted etch resist, then chemicals eat away the exposed copper. Once the copper is gone, the underlying board can be cut again with the laser to make through-holes. No drilling required! After some setup and practice, you should get reliable boards with 8-mil trace/space and hundreds of holes in about 2 hours. You can even cut internal routing and odd board-shapes!

Via Hacked Gadgets.

Digitally controlled HIFI amp with 4 way mixer

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Acidbourbon posted a step by step guide of his digitally controlled HIFI amp with 4 way mixer build:

The amplifier section is trivial. You just buy a TDA1554Q, bolt it to the inside of an aluminum box, solder some resistors and capacities to the pins of the IC according to the application note in the datasheet and you have a small HiFi amplifier.
Because the volume control has to be digital, I’m using digital potentiometers. Sadly there are no (affordable) logarithmic digipots available. However I found this method which employs a linear potentiometer in combination with a fixed resistor to “fake” a logarithmic potentiometer.

Arduino based auto trigger spray keeps cats at bay


Curiosity killed the cat, but this project only sprays them with water.
Tinkernut posted this humorous project useful for animal control in the kitchen. It uses an Arduino/PIR combo to sense motion and activate the auto trigger on a Raid spray bottle (of course, after emptying and thoroughly cleaning the Raid bottle.) When strategically placed on a kitchen counter, it sprays water at any errant feline that happens by.

Via Tinkernut.

Using touch screen as remote control

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Bajdi  wrote an article on using an Arduino Due with a 5inch touch screen and a wireless nRF24L01 transceiver as a remote control:

One of the things I wanted to try out was using the touch screen as a remote control. I have a lot of cheap nRF24L01 modules so I soldered one to the adaptor shield. Thankfully someone has ported the RF24 library to make it work with the Arduino Due. I made a simple sketch to remotely control 4 leds with the touch screen using the wireless nRF24L01 modules

Check out the video after the break. Continue reading “Using touch screen as remote control”