A distributive method to increase the analogic output (D/A) resolution of a microcomputer

This paper describes a simple and efficient method to increase the D/A output resolution of an 8-bit microcomputer, as exemplified on the Apple II. The “distributive method” can increase the final output resolution up to 32K with two 8-bit analogic channels. A simple interface based on balanced sets of resistors and driver software are described. Some applications are also reported.     

Autoranging amplifier expands computer’s A/D sensitivity by two decades

This device accepts an analog signal from 0 to +14 V, automatically changes gain to condition the analog output to the limits of a ±1 V A/D converter, and transmits the gain mode as two digital bits. A computer with a 10-bit A/D converter and two sense lines uses this device to obtain the dynamic range of a 16-bit A/D converter. The relatively simple principle of the circuit may be of interest to expand the voltage sensitivity range of other analog devices for slowly changing signals.     

A method for utilizing a single port for multiple functions on the IBM PC or compatible system

Psychological experiments often require the control of a large number of output lines; unfortunately, the IBM PC provides only 32 8-bit ports through which communication may be implemented without risk of conflict with other software/hardware. A single 8-bit port may be used to control a large number of devices by adding appropriate decoder logic between the computer’s port and the devices that are to be controlled. Software and hardware are presented that illustrate this technique by controlling an 8-digit light-emitting diode display with a single IBM PC output port.     

A six-channel PDP-8 interface for nerve impulse data

An interface operating on the I/O bus of the LINC-8 has been built which accepts up to six channels of nerve impulse data simultaneously at rates up to 4,000 pps/channel. By means of a 100-KHz clock and a 17-bit counter, the time of occurrence of each nerve impulse is strobed into one of six 17-bit buffer registers. The strobe causes a program interrupt to occur. Two I/O instructions are used to read the buffers into the PDP-8 accumulator. Additional instructions for skipping on data or overflow, enabling the counter, clearing the overflow flag, and clearing the counter are available.     

Time-interval acquisition on a 6502-based microcomputer

A versatile machine language subroutine and accompanying interface circuitry enable a 6502-based computer to collect time intervals between data events that can be represented by voltage transients. Intervals within the range of 150 microsec to 13.98 min can be collected with a resolution of ±25 microsec. Electrical interface circuitry includes signal conditioning and optical isolation and also allows user-specification of threshold levels on the data line. The machine language software timing routine and sequential interval handler include a 24-bit interval timer, a 16-bit interval counter, user-specified number and length of acquisition periods, and an out-of-memory tester. Although presented for implementation on the Apple II series of microcomputers, the transportability of the routine to other 6502-based machines is addressed.     

A versatile memory-mapped I/O interface for microcomputers

An inexpensive and easy-to-bulid input/output interface capable of driving the electromechanical loads (relays, solenoids, dc motors, etc.) and incandescent lamps is described. The interface hardware is based on the Commodore VIC-20 microcomputer. The design is adaptable to most 8-bit microcomputers.     

An oscilloscopic point-plotter interface for 8-bit microcomputers

An inexpensive interface capable of driving high-resolution point-plotting systems is described. Specific examples of modifications to the electronic hardware are detailed for the Rockwell Aim 65, but the design is readily adaptable to most commercially available 8-bit microcomputers. Some comparisons are drawn between salient features of raster-scan and of point-plotting display systems.     

Runword: An IBM-PC software package for the collection and acoustic analysis of speeded naming responses

Researchers generally collect two dependent measures from most types of speeded responses: reaction time and error proportion. Recently, experimenters have tested lexical theories using alternative empirical measures, such as response force in decision tasks and response duration in naming tasks. We offer a set of software tools that expands the battery of dependent measures normally available to naming experimenters to include various duration and intensity measures of digitized voice recordings. This article explains the functionality, programming logic, and theoretical motivation behind each measure, as well as the software to support digitized naming experiments. The software runs in DOS on IBM-PC-compatible hardware with SoundBlaster 16-bit sound cards, and it takes advantage of the decreasing costs of hard-drive space and digital sound cards.     

Millisecond precision psychological research in a world of commodity computers: New hardware,new problems?

Since the publication of Plant, Hammond, and Turner (2004), which highlighted a pressing need for researchers to pay more attention to sources of error in computer-based experiments, the landscape has undoubtedly changed, but not necessarily for the better. Readily available hardware has improved in terms of raw speed; multicore processors abound; graphics cards now have hundreds of megabytes of RAM; main memory is measured in gigabytes; drive space is measured in terabytes; ever larger thin film transistor displays capable of single-digit response times, together with newer Digital Light Processing multimedia projectors, enable much greater graphic complexity; and new 64-bit operating systems, such as Microsoft Vista, are now commonplace. However, have millisecond-accurate presentation and response timing improved, and will they ever be available in commodity computers and peripherals? In the present article, we used a Black Box ToolKit to measure the variability in timing characteristics of hardware used commonly in psychological research.     

Graphic bar display of on-line physiological data using a minicomputer,DAC, and conventional servo recorder

A method is described for providing an on-line bar graph display of physiological data. A conventional servo recorder is coupled with an 8-bit digital-to-analog converter, and provides a low-cost, hard-copy graphic display peripheral that can be added to any laboratory type minicomputer system with buffered output data lines. The graphic display technique requires minimal memory allocations and a simple software algorithm to provide a flexible graphic system that can accommodate various types of biological data.     

Behavioral assessment of eating patterns and blood glucose in diabetes using the Self-Monitoring Analysis System

The Self-Monitoring Analysis System is a set of microcomputer programs that were developed to remove clinical judgment from the task of behavioral assessment using self-monitoring diaries. The program is written in Turbo Pascal and runs on MS-DOS (16-bit) or CP/M (8-bit) microcomputer systems. The program allows the user to custom design data bases with hundreds of binary, categorical, integral, and real variables. Full-screen data-entry forms can be custom designed, and random access files allow for flexible data entry and editing. The program makes extensive utilization of Pascal’s very flexible data structure capabilities. Dynamic allocation of memory allows the program to maximize its use of available RAM. Data from a patient with diabetes is presented as a case study illustrating the system’s utility.     

A Macintosh II psychophysiology system

An integrated data-acquisition and -analysis system for doing psychophysiology on Macintosh II computers is described. Plug-in cards allow the system to meet the technical demands of psychophysiological research—including 24-channel, 12-bit resolution and sampling of scalp potentials taken at a sampling rate of 400 Hz. Use of a compiled graphical data-flow language to program this equipment brings the implementation of sophisticated methods within the reach of many experimenters. Some applications of this system to multichannel evoked potential research are described, including P50 conditioned-disinhibition and augmenting/reducing experiments. Extensions of the system into such areas as topographical brain mapping are also noted.     

EMDISP: A visual display system with digital and analogue sampling

EMDISP provides general-purpose assembly language routines that can be called from higher level languages to produce specific application programs for experiments involving visual displays, manual responses, and analogue sampling (e.g., eye movement recording). The display system assumes the use of fast-phosphor oscilloscopes driven by 12-bit digital-to-analogue converters (DACs) to produce point-by-point displays. Within these limitations, EMDISP offers a flexible and efficient method of generating displays, in which elements of a complex display are defined as separate “pictures” and are controlled independently. High-level control of digital and analogue sampling are provided, enabling interactions between the contents of the display and analogue and digital inputs.     

A hardware multiplier/divider for the PDP 8S computer

This paper outlines the design of a multiplier/divider being developed for the PDP-8/S. The unit will carry out the required function on two 12-bit signed numbers (using 2's complements for negative numbers) and produce a correctly signed result. All data transfers will be through the programmed I/O channel, no data break facility being required. The estimated time taken for the operations is 96 microsec for multiplication and 176 microsec for division, which is considered reasonable in comparison to the I/O times of 38 microsec. The total material cost is estimated at $1,500. Some variations of the basic unit are also discussed.     

A parallel printer port to matrix driver with high current DAC output

The circuit described here takes data from an IBM PC, or a compatible, parallel printer port and expands it to drive a matrix of devices. The matrix size is user definable up to a maximum size of 16 by 16 elements (256 elements), but as drawn is an 8 by 24 matrix (196 elements). Each element in the matrix can be inductive, resistive, or capacitive, with a maximum voltage of about 18 volts, and a total maximum current of 15 amps peak, or 8 amps continuous with adequate heat sinks (dissipating 80 watts maximum per driver device). Several matrix elements may be asserted simultaneously. The voltage applied across the matrix “rails” is controlled by a digital-to-analog converter with 4096 steps (12-bit accuracy).     

A low-cost high-speed digital data acquisition and display system

A flexible and inexpensive data acquisition and display system based upon the KIM-1 microcomputer module is described. A simple signal-conditioning circuit and program are shown that will allow events to be counted at rates to 1,000/sec and stored in successive time bins. The program counts events from each of two event detectors and stores the count of each detector in an independent set of time bins. Up to 127 16-bit bins are available to each event detector and bin width can be varied from 1 msec to 1 min. A separate input can be used to time-lock data collection to a specific stimulus allowing poststimulus histograms or IRTs to be collected. The collected data can be sequentially displayed as a decimal number on a built-in LED display and stored for later analysis on an inexpensive audio cassette recorder.     

Experimental RunTime System: Software for developing and running reaction time experiments on IBM-compatible PCs

The Experimental RunTime System (ERTS) is a recent addition to the small collection of commercial software packages available for writing and running reaction time experiments on IBM-compatible PCs. Experiments are written using any text editor and a relatively small set of ERTS commands. Millisecond timing is provided by a software timer with no additional hardware requirements. All displays are in high-resolution VGA graphics. The Creative Labs Soundblaster card is supported in 16-bit mode, but is not required for simple tone generation. Voice-key support is available via the Soundblaster card. Keyboard, mouse, and external keys may be used as reaction keys, and the mouse or a joystick may be used as a tracking device. The stimulus-centered design and powerful display control commands of ERTS make it appropriate for developing a wide range of trial-based experiments.     

Aggregation in memory of episodic influences on rule-guided decisions

The authors confirmed E. Z. Rothkopf and M. L. Dashen's (1995) finding that specific problem context, such as thematic surface features, forms associative connections with deep problem features and thus speeds particular decisions (particularization). In 5 experiments, using a 3-bit decision task and pre-memorized decision rules, the authors found that the ability of a situational context to reinstate was decreased by its replacement by another modal surface context. Context reinstatement, as measured by decision speed, depended on both global and recent local densities of specific problem features linked to a particular decision. The authors' results are consistent with J. R. Anderson and L. J. Schooler's (1991) needs/odds analysis and suggest a push-down file model for diverse context influences as a mechanism for responding to changing situational demands.