Microcomputer control for psychoacoustic experiments

Abstract

We describe a psychoacoustics laboratory with microcomputer control of stimulus generation and data acquisition. The control hardware is based on a MOS Technology 6502 microprocessor with 6 K of ROM and 13 K of RAM. Interfacing is through programmable circuitry using MOS Technology 6532 chips. Analog signal generating equipment is controlled by 16 logic lines and eight 12‐bit DAC's. Interaction with subjects is through 48 input/output logic lines and a 16‐channel 12‐bit ADC. Experimental data is stored in a fixed, standard format; it can be displayed on a video screen, printed on paper, and/or stored on standard audio cassettes. Software is based around the KIM operating system using subroutine calls rather than a high‐level language. The software control package is specialized for counting, timing, and sequencing stimuli and interacting with subjects. The system presently runs forced choice, method of adjustment, and up‐down tracking routines. Logical construction of experimental programs from the modular subroutines can be simpler and faster (though less flexible) than FORTRAN programming of a large system.