App note: Buried capacitive sensors for tamper protection

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A short app note from Silicon Labs on burying pads to prevent snopping on keypads. Link here (PDF)

An individual’s financial matters are increasingly electronic in nature and decreasingly interpersonal. As financial institutions replace human interaction with electronic interfaces such as ATMs, the need to make electronic circuits tamper-proof becomes critical. A typical numeric keypad for financial transactions may contain up to hundred or more tamper prevention and detection features. Tamper detection circuits raise alarms and disable functionality, while tamper prevention features are designed to prevent intrusions and breaches. This application note addresses the elimination of copper pads on the accessible top surface of printed circuit boards (PCBs). Burying traces to internal layers of a PCB prohibits electrical contacts from snooping on copper elements within the PC board.

App note: Driving E ink segmented displays

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Application note on driving E Ink displays from Renesas. Link here (PDF)

E Ink segmented displays are direct drive displays consisting of E Ink Vizplex Imaging Film sandwiched between two electrode layers, the top plane and the backplane, and then encased in an environmental barrier solution to protect the film and the segment electrodes. To get the most from E Ink segmented Displays, you need to be aware of proper design and implementation. Your reward will be sharp, precise images, a pleasant transition from one image to the next, and a long battery life.

SQUIX ESP8266 based e-paper WiFi weather station

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Erich Styger documented his experience building Daniel Eichhorn’s e-paper weather station with a custom enclosure:

Using e-paper for a weather station is an ideal solution, as the data does not need to be updated often. By default, the station reaches out every 20 minutes for new data over WiFi and then updates the display. Daniel Eichhorn already has published kits for OLED (see “WiFi OLED Mini Weather Station with ESP8266“) and touch display (see “WiFi TFT Touch LCD Weather Station with ESP8266“). I like them both, but especially the TFT one is very power-hungry and not really designed to work from batteries. What I would like is a station which can run for weeks.

More details at MCU on Eclipse site.

MickMake Mail #20: SAMG53, SAM4S & Anet 3D printer // News

Not much coming in to the MickMake studios this week so I delve in to a 3D printer I received from BangGood a couple of weeks back. SAM4S Xplained Pro I bought a couple of these for a project I’m working on that relies heavily on ultra low power consumption. Continue reading MickMake Mail #20: SAMG53, SAM4S & Anet 3D printer // News

Posted by Mick on MickMake - Live. Learn. Make.

PIC18 four-channel DMX relay controller

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Glen Akins has a nice build log on his four channel DMX-controlled relay, that is available on GitHub:

 Halloween was right around the corner and I needed a timer with a bunch of relays to trigger some store-bought props and a fog machine periodically. (Mental note: read fog machine specs carefully—not all come with timer remotes.) My first thought was an Arduino and cheap relay board. Second thought was to build something with a micro and some relays. Third thought was that if I’m going to build something, might as well add DMX and package it up into a neat enclosure. Hence, the four channel DMX-controlled relay project was born.

See the full post on his blog.

A Certificate Authority with OpenSSL

The security of several protocols is implemented using SSL certificates. Usually, those certificates are created by public certificate authorities. If we’re connecting to a website (HTTPS protocol), the browser we’re using must recognize the identity of the CA that signed the server certificate, otherwise an error message is shown:

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A CA “creates” a new certificate signing it with its own certificate… you can find more than one level, for example the Google certificate (in blu) has been signed by an intermediate CA (green), whose certificate is signed by a root CA (red):

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To consider the certificate valid, the browser or the operating system must have the certificates of the CAs that signed it in their trusted repository:

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Today I’ll explain you how to create a CA using an opensource tool, OpenSSL. This CA will be very useful everytime you’ll need an SSL certificate for internal use.

After having installed the OpenSSL tool, create a new folder dedicated to the CA (in my example, MyCA).

Within the new folder, create some empty folders and files:

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Open the “serial” file and type the value 1000 (this will be the serial number of our first certificate).

Now download from my Github repository the openssl.cnf file and copy it in the MyCA folder. This file contains the whole configuration of the Certificate Authority.

Open the file and change the dir parameter with the path of your CA’s main folder:

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Now generate the private key of your CA. All the following commands must be issued in the MyCA folder:

openssl genrsa -aes256 -out private/ca.key.pem 4096

You’ll be prompted for a password; it’s very important to note it down because you’ll need it everytime you’ll use the CA.

Now generate the self-signed certificate for the CA:

openssl req -config openssl.cnf -key private/ca.key.pem -new -x509 -days 3650 
 -sha256 -extensions v3_ca -out certs/ca.cert.pem

OpenSSL will ask some information; the most important of which is the Common Name, that is the name which identifies your CA:

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Let’s now generate client or server certificates using your new CA.

Generating a new certificate starts from a private key, that will be safely stored on the system which will use the certificate (for example on the webserver that will publish the site in HTTPS). Then you have to generate a CSR (certificate signing request) from the key. The CSR is the file that will be signed by the CA to produce the final certificate.

As CA administrator, you can receive the CSR file from the end user; alternatively you can generate it using OpenSSL:

1. generate the private key (RSA algorithm) for your new certificate:

openssl.exe genrsa -out server.key

2. generate the CSR file:

openssl.exe req -new -config openssl.cnf -key server.key -out server.csr

Again you are prompted for some information, including the name (common name) of your server.

Now generate the certificate signing the request:

openssl.exe ca -config openssl.cnf -extensions server_cert 
 -notext -in server.csr -out server.cer

Confirm with two Y (yes) and your new certificate is ready:

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Building a Midi hat and jukebox using the Raspberry Pi

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Dr. Scott M. Baker has published a new build:

I picked up a Roland SC-55 to use with my retrocomputer setup recently, and I figured it would be cool to turn the thing into a standalone midi jukebox, so that no “computer” is required. I also figured this would be relatively easy, using a raspberry pi as the controller to drive the SC-55. My first step was to figure out how to get MIDI out from a raspberry pi. One option would have been to purchase a USB-MIDI adapter. This would have worked, but I really wanted to develop a native raspberry pi MIDI interface rather than using USB. MIDI is a fairly simple interface, and the raspberry pi has built in serial capability, so this ought not to be too difficult.

Project details can be found on Dr. Scott M. Baker’s blog.

Check out the video after the break.

App note: Grid-connected solar microinverter reference design

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A good read from Microchip on the theory behind inverter design connected to grip power. Link here (PDF)

There are two main requirements for solar inverter systems: harvest available energy from the PV panel and inject a sinusoidal current into the grid in phase with the grid voltage. In order to harvest the energy out of the PV panel, a Maximum Power Point Tracking (MPPT) algorithm is required. This algorithm determines the maximum amount of power available from the PV module at any given time. Interfacing to the grid requires solar inverter systems to abide by certain standards given by utility companies. These standards, such as EN61000-3-2, IEEE1547 and the U.S. National Electrical Code (NEC) 690, deal with power quality, safety, grounding and detection of islanding conditions.

App note: On-grid solar microinverter on Freescale MC56F82xx/MC56F82xxx DSCs

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Application note from Freescale Semiconductor about microinverter solution develop together with Future Electronics. Link here (PDF)

In recent years, demand for renewable energy has increased significantly. The development of devices utilizing clean energy such as solar, wind, geothermal, and fuel cells attracts more and more attention. Solar energy harvesting is developing fast and will play a more important role as a global energy source. One of the ways to capture solar energy is via photovoltaic power generation systems, which are connected to the grid through power inverters. Therefore, many companies are focusing on development of photovoltaic grid-tie inverters. Freescale offers digital signal controllers, the MC56F8xxx family, that are well suited to ongrid solar inverter designs.