PS/2 Keyboard to Parallel Adapter Older machines and single-board computers, particularly ones from the mid-to-late ’70s through the very early ’80s often used a parallel keyboard input. It was very common during this time for a hobbyist to ‘roll their own’ system with parts from different sources. Keyboards with a 7 or 8 bit parallel ASCII output were available from several sources, but are no longer manufactured. Occasionally you will see one on eBay, but usually for an exorbitant price.

Motivation I enjoy collecting older computers, particularly ones from the mid-to-late 1970s through the early 1980s that run CP/M. Machines from this period commonly have 8" or 5.25" floppy drives. Finding working 8" or 5.25" floppy drives is becoming increasingly difficult. So is finding media. To address this problem for his Atari ST, Jean-Fancois Del Niro created HxC2001, which is a hardware-based floppy drive emulator. Over time support for different drive types and floppy image formats has been added.

Binterm - An Ultra-Simple Terminal Program I work on a wide variety of microcontroller-based systems. My preferred development platforms for cross-compiling are Linux and Mac OS X. Frequently, I need interact with the serial port on the microcontroller system for development and testing purposes. Both Linux and Mac OS support the ‘screen’ command natively. You can use the screen command to connect serial devices like this: screen /dev/serial.device 9600 (or whatever baud rate is necessary) That works just fine, as long as you dont need to dump the output from your microcontroller (uC) system in hex, log it to a file, or any number of other functions.

Motivation Recently, I began a project to build a (reasonably) accurate 3-axis magnetometer. One of the challenges in building a magnetometer is calibrating it with a known magnetic field. Creating a known magnetic field requires using a calibration coil with a known current flowing through it. If you want to make multiple (and consistent) measurements, it is very convenient to have the current under computer control…and that is where the Programmable Current Sink (PCS) got its’ start.

The ionosphere and geophysics have always been “hobbies” of mine. Recently, I began a project to build a 3-axis magnetometer. The first iteration of this project uses FG-3+ fluxgate sensors available from FG Sensors. These sensors are very similar to the sensors once produced by Speake & Co (long out of business). The FG-3+ sensors output a variable period square wave based on the magnetic field strength and direction. The frequency of this square wave typically ranges between 40kHz to over 120kHz.

Design For years, I had been running a home-brew weather station based on PIC microcontrollers, analog temperature and humidity sensors and a BME180 pressure sensor housed in a Stevenson Screen. It worked reliably for about 6 years, until a lightning storm near-hit cooked the electronics. I decided that it would a great time for an upgrade. In addition to temperature, humidity and pressure, I also wanted to measure rainfall, wind speed, and wind direction.

A High Bandwidth Low Noise Optical VLF Link This is an article that I wrote which first appeared on Renato Romero’s website vlf.it. It describes the design, characteristics and use of a high bandwidth, low noise optical system for connecting a VLF receiver to a data sampling system. This easy to build, inexpensive system has a flat response to over 200KHz, and a noise curve well below the VLF band.