Interfacing a 4×4 Matrix keypad with an 8-Bit GPIO expander

app_note

An application note from Microchip: Interfacing a 4×4 Matrix keypad with an 8-Bit GPIO expander

This application note discusses interfacing a 4×4 matrix keypad with MCP23X08 8-Bit GPIO Expander. This application note references the MCP23X08/17 GPIO Expander Keypad/LCD Demo Board (GPIODM-KPLCD). GPIO Expanders provide easy I/O expansion using standard serial interfaces such as I2C and SPI. They are especially useful in applications where pin count is limited on the microcontroller unit (MCU) or if remote inputs / outputs (I/O’s) are needed. It is best to think of an 8-bit GPIO Expander like adding another 8-bit wide digital port to the MCU. This application note does not detail all of the features of the MCP23X08. Refer to the MCP23008/MCP23S08 Data Sheet, “8-Bit I/O Expander with Serial Interface” (DS21919) for more information.

Easy Pulse V 1.1 project update

EasyPulseV1.1Board3

Raj previously designed the Easy Pulse heart rate sensor. Now he informs us of an update: “I would like to inform you about the release of a new version of Easy Pulse sensor. The Easy Pulse sensor is designed for hobby and educational applications to illustrate the principle of photoplethysmography (PPG) as a non-invasive optical technique for detecting cardio-vascular pulse wave from a fingertip. It uses an infrared light source to illuminate the finger on one side, and a photodetector placed on the other side measures the small variations in the transmitted light intensity. The variations in the photodetector signal are related to changes in blood volume inside the tissue. The signal is filtered and amplified to obtain a nice and clean PPG waveform, which is synchronous with the heart beat.”

The major components are an MCP6004 Op-amp and HRM-2511E transmission PPG sensor.

The schematic and details can be found at EmbeddedLab.

Via the contact form.

RTL-SDR dsd tutorial: monitoring P25 digital voice

dsd
The crew over at RTL-SDR.com has posted a simple tutorial on using the RTL-SDR dongle and free SDR# and Digital Speech Decoder software (dsd) to monitor P25 digital radio voice comms. They describe, “Digital radio voice communications are becoming more commonly used in the radio spectrum. This is due to the various improvements offered over traditional analogue voice radio systems. Unfortunately for radio scanner hobbyists, digital radio is difficult to receive, as special radio scanners which can be expensive are required to decode the digital audio. Additionally, digital radio systems can be encrypted making it impossible for communications to be decoded by a hobbyist. However, most users of digital radio do not bother to encrypt their systems as it can introduce lag and extra battery drain in portable radios.

The most common digital speech codec is APCO P25, which dsd is able to decode. Dsd is also capable of decoding other common digital codecs such as DMR/MOTOTRBO and ProVoice which no hardware scanner is currently capable of.”

One part of this project that isn’t open source is their use of Virtual Audio Cable software to route the SDR# output to the DSD.

Free PCB Sunday: Pick your PCB

Dangerous DSO v1 - Click Image to Close

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: Guidelines for reliable long line 1-wire networks

app_note1

Here’s a guidelines for reliable 1-Wire Network from Maxim:

The 1-Wire protocol was originally designed to facilitate communication with nearby devices on a short connection. 1-Wire was also a way to add auxiliary memory on a single microprocessor port pin. Methods were later developed to extend the 1-Wire protocol to network applications well beyond the size of a circuit board. This document discusses various aspects of 1-Wire networks and provides design guidelines for their reliable operation. Several appendices address fine-tuning the 1-Wire bus interface and illustrate 1-Wire communication waveforms in various conditions.

Dead drop file sharing revisited

deaddrop2
The concept of dead drops, where USB thumbdrives are installed in public places for the distribution of files “off the grid” has been a popular topic. Now Steve Schuler writes in with his new take on this concept currently featured in Science 2.0. His article describes low tech ways to place dead drop drives in public places without permanently attaching them to a structure. He also covers topics relating to concealment of the drives and some novel ideas relating to encrypting the location of drives.

Via the contact form.

Raspberry Pi 3D printer demonstration

Jon Wise demonstrates his Raspberry Pi 3D Printer, he is using a pen in the demo but it can use an extrude to print items. The mechanical movements leek very complex when compared to a standard XY table that is controlled using 2 stepper motors. The Pi has enough number crunching ability to get the job done though. I can’t wait to see this printing a complex shape, the movements are interesting to watch, it reminds me of the robot hands that use angular joints to move around.

Via Hacked Gadgets.

Building a sweep generator for BK 4011

sweepgenerator-W600

Kerry Wong documented his sweep generator build:

In this post I will show you a simple sweep generator I built. It can be used to generate both the sweep waveform and synchronization signal needed for any function generator that has a VCG/VCO input. The sweep frequency can be adjusted from under a Hertz to several kHz. The sweep waveform can be switched between linear and logrithm modes and can be easily extended to accommodate other arbitrary waveforms.

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 April 19, 2013

BP_EK_E12_overview2

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
  • 3D model on Monday
  • Eagle parts and tips on Tuesday
  • Free PCBs via Twitter on Tuesday
  • A new tutorial on Wednesday
  • Workshop video on Thursday
  • Weekly roundup and preview every Friday

Bus Pirate V4 acrylic magnet case

IMG_1097-W600

Here’s another cool acrylic magnet case for Bus Pirate v4 made by Diego with his CNC machine.

Hi, i’ve made a case for my BP V4 with my cnc (Acrylic & Magnets), you can find all the file on my website

Via the forum.

More cool DIY cases here.

Check out our  Bus Pirate v4 Acrylic case kit v1  now selling at Seeed for $3.

You can get a Bus Pirate v4 for $40, including worldwide shipping.

MIDI OUT for vintage Korg CX-3


Michael from AcidBourbon writes, “This project is about adding a MIDI output to a vintage organ, the Korg CX-3 (famous Hammond compact organ clone). My Korg was built in 1979, so before the introduction of the General Midi standard. But tapping into the right (only three) conducting paths on the main PCB and using a level converter plus an ATTiny2313 lets you add a MIDI-Out very inexpensively.”

Details on this project, including schematic and link to the MCU firmware can be found at AcidBourbon.

Via the contact form.

Little Bird Electronics “Magpie” Arduino-compatible board review

topss

Tronixstuff has a review of “Magpie” Arduino Uno-compatible board from Little Bird Electronics:

Starting with the subject of this review – the “Magpie” board from Little Bird Electronics in Australia. It seems that a new Arduino-compatible board enters the market every week, thanks to the open-source nature of the platform and the availability of rapid manufacturing. However the Magpie isn’t just any old Arduino Uno knock-off, it has something which helps it stand out from the crowd – status LEDs on every digital and analogue I/O pin. You can see them between the stacking header sockets and the silk-screen labels.

Check out the video after the break.

Continue reading “Little Bird Electronics “Magpie” Arduino-compatible board review”

LaserOrigami: Laser-cutting 3D objects

Laser_cutting_3D

Researchers at Germany’s Hasso Plattner Institute have developed an amazing new Laser cutting 3D objects, the LaserOrigami:

LaserOrigami is a rapid prototyping system that produces 3D objects using a laser cutter. LaserOrigami is substantially faster than traditional 3D fabrication techniques such as 3D printing and unlike traditional laser cutting the resulting 3D objects require no manual assembly.

Via Hacked Gadgets.

Check out the video after the break.

Continue reading “LaserOrigami: Laser-cutting 3D objects”

STM32F4 debug board v1.0 Rev2

STM32F4_Debug_1_0_Rev2_Top-W600

TitanMKD posted an update to his STM32F4 based debug board we covered previously:

 This board is intended to be used as a portable multi-purpose debug/hack tool with very fast peripherals and MCU and use standard Dangerous Prototypes Sick Of Beige DP6037 case format
A full open source firmware is planned using chibios and like Bus Pirate v3/4 user interface through serial terminal using the microUSB connector (the development of firmware will be during 2014 as i’m very busy to finish other projects).
The new revision v1.0 Rev2 fix routing problem and add a new feature a 2nd micro USB connector, which can be used as USB OTG FS DFU (device firmware upgrade) to avoid requirement of a JTAG probe for programming the firmware.
Depending on feedback this board could be connected to any Android phone/tablet (through microUSB connector) for portable usage to debug/hack electronic stuff everywhere.

Stepper motor bluetooth serial driver (Attiny85 & L293D)

thefinishedboard

Trandi blogged about his Stepper motor bluetooth serial driver project:

How to put together a simple bluetooth driver for a nice little stepper motor (Mitsumi M35SP-11HPK) that I salvaged from an old Canon printer.
It uses a small Attiny85 (the more I use them the more I love them ! :) ) programmed in Arduino, a L293D H bridge, a few discrete components and a bluetooth to serial adapter

Check out the video after the break. Continue reading “Stepper motor bluetooth serial driver (Attiny85 & L293D)”

TIDeals: eZ430-Chronos watch again

ez430-watch
If you missed it before, TI is offering the Chronos Watch as their current week’s deal at $38 (plus shipping.) The eZ430 deal includes the wireless enabled watch, CC1111 USB RF access point, and a CD containing software and documentation. This is the watch featured in a recent post on hacking RF devices in the ISM bands using the Chronos watch with the modded ChronIC firmware.

The watch is available in three separate models each covering one frequency range, either 433, 868 or 915 MHz.

TI is fulfilling the deals directly via DigiKey. (The watch sells for $58 on the TI eStore site.)