Instrument Interface VCL Delphi Component

Free component for real time access to a hardware interface containing digital ports and analog inputs and outputs via digital-to-analog and analog-to-digital converters. Full source is included for educational purposes. Works with the range of PC cards from www.instrument-science.com using the VXD for interrupt time processing.

The component Iscard has properties to access up to 64 analog outputs via Digital to Analog Converters (DAC's) with 12 bit or 16 bit resolution and methods to read voltages from upto 32 analog inputs via Analog to Digital Converters also with 12 bit or 16 bit resolution. Additionally 64 digital outputs and 32 digital inputs are also available. The component also provides access to maximm of 4 pulse counters.

This component was developed to work with the Instrument Interface ISA card (IS 1006) from Instrument Science (http://www.instrument-science.com). The real time access to the card's hardware registers is realised using a virtual device driver (ISCARD.VXD) provided with the card.

The component can access up to 4 interface cards. Always one of these cards is selected by the SelectedCard property.

The AnalogOut:TAnalogOut and DigitalOut:TDigitalOut array properties can be changed at the design time. This will define the initial values of the hardware outputs when the application starts.

Run time properties AnalogIn[i:integer]:double and DigitalIn[i:integer]:boolean provide the current values read from the hardware inputs. These values are periodically refreshed by the VXD driver with a period set between 0.25 ms and 2 ms.

The following properties:

    property CountPulses:cardinal read GetCountPulses;
    property CountTime:double read GetCountTime;

are used to read a number of pulses acquired in the hardware counter and the time duration elapsed since the last use of the ResetCount method.

The read only property BasePort identifies the selected card by its address on the I/O bus.

In the directory Demo there is a very simple example of the ease of use of this component.

I hope that you find the source code instructive and perhaps useful for development of similar hardware oriented projects.

Patrik Spanel, January 2001