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23 Sep 2011

pyroelectro.com writes:

The keyboard is the most common way for humans to input information into a computer. It has been around since before computers were main-stream and everyone was still using typewriters. Because of this prevalence in society, it’s important that we understand how to interface to the basic PS/2 keyboard.

This article will describe and show you an example of how to create a system capable of interacting with a keyboard in order to understand what keys have been pressed. The example system will be built on a breadboard using a PIC microcontroller to communicate with the keyboard and display output.

PS/2 Keyboard Interface - [Link]

7 Sep 2011

VT220 serial console (circa 1983) set up as a terminal for Mac Pro (2010) – [via]

My biggest source of information getting this going was Paul Weinstein’s post about setting up an Apple IIc as a terminal for his Mac mini (which is similar, but not quite the same since the IIc still has to emulate the terminal in software). I got the same USB-to-serial adapter, a Keyspan USA-19HS ($27), which has Mac drivers that I can happily confirm work well with 10.7 Lion. I also needed a null modem cable ($7) and 25-pin female/female converter ($4) to connect it to my VT220.

At first I used the same method as Paul to get it working, gluing together the terminal and OS with a utility called screen. As Paul notes, this is less than desirable. It still requires you to open a software terminal to make the connection, and you’re still operating through a layer of emulation. On most Unixes you can simply add a line to /etc/ttys and everything just works via getty, but apparently this has been disabled in OS X since 10.5.

Eventually I found this page, which explains the problem and how to fix it. After adding a line in /etc/gettytab to manually set the terminal type to vt220-8bit everything works perfectly! A real hardware terminal directly connected the old fashioned way, with no emulation. Awesome

VT220 serial console (circa 1983) set up as a terminal for Mac Pro (2010) - [Link]

12 Aug 2011

Here’s an article that presents a rather innovative look at how to spoof magnetic card readers. The spoofer uses an atmega168 connected up to an electromagnet. The article has the source code, hardware schematic and action shots, don’t miss it! [via]

Magnetic Card Spoofer - [Link]

9 Jun 2011

Squonk found this simple VGA interface for FPGA board. [via]

Simple VGA interface for the XuLA FPGA board – [Link]

6 Jun 2011

3in1 universal converter. Based on FTDI 232R chip seen as normal COM port, and two serial converters MAX232 and MAX485. Allow to be used as RS232, RS485, or UAR TTL converter. Connections parameters can be set through the system, as in normal COM port. Supported speeds: 110 to 921600bps.

3in1 converter – USB to RS232, RS485, UART - [Link]

26 May 2011

This is a low-cost prototype electrooculography (EOG) system, based on the ATmega328P, that allows people with motor disabilities to write text on a screen using only eye movements. Luis explains: [via]

The human eye is polarized, with the front of the eye being positive and the back of the eye being negative. This is caused by a concentration of negatively charged nerves in the retina on the back of the eye. As the eye moves the negative pole moves relative to the face and this change in the dipole potential can be measured on the skin in micro volts. To translate this voltage into a position, two sets of electrodes are used to measure the differential voltage in the vertical and horizontal direction, on this project, however, just horizontal movements are recorded.

Honduran High Schooler’s Low-Cost Eye-Controlled Interface – [Link]

17 May 2011

Matt writes in about RTS/CTS handshaking and waveforms…

I recently had the need to add RTS/CTS handshaking to the serial connection between my PC and my ATMega. I struggled with it for a time due to some misunderstandings on my part, and because I couldn’t find a writeup which described how the handshaking is supposed to work, and (more importantly for me) how it’s supposed to look. I eventually got it to work, and wrote it up in a way that would’ve been useful for me when I was trying to figure out how to make it work.

RTS/CTS handshaking and waveforms – [Link]

9 May 2011

dangerousprototypes.com writes:

The Ben NanoNote is a cheap netbook without VGA video output. This hack connects a VGA cable to the SD card slot and uses software to bitbang a VGA signal.

This hack is accomplished using the Universal Breakout Board (UBB) which slides into the SD slot providing access to these signals. The UBB interfaces with the VGA connector via a handful of resistors. The schematic and code for the Ben are posted on the project’s site.

Bitbang VGA from an SD card slot – [Link]

16 Apr 2011

McZ found a sim card power supply with level translator:

The TXS4555 is a complete Smart Identity Module (SIM) card solution for interfacing wireless baseband processors with a SIM card to store I/O for mobile handset applications. The device complies with ISO/IEC Smart-Card Interface requirements as well as GSM and 3G mobile standards. It includes a high-speed level translator capable of supporting Class-B (2.95 V) and Class-C (1.8 V) interfaces, a low-dropout (LDO) voltage regulator that has output voltages that are selectable between 2.95-V Class-B and 1.8-V Class-C interfaces.

1.8V/3V sim card power supply with level translator – [Link]

31 Mar 2011

pyroelectro.com writes:

Many different types of communication protocols exist and the PIC is able to use quite a few of them. USB, RS232 and Parallel are all common forms of digital communication that use a unique method for transferring data. Today we will focus on a protocol called I²C (pronounced I-squared-C).

PIC I2C Interface Tutorial – [Link]





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