Parallel Port Interface ADC for Real Time Data Acquisition

A parallel port interface ADC for real time data acquisition has been designed and developed indigenously. The ADC has been designed by utilizing the data input capabilities of the computer parallel port. In addition to a basic ADC chip, it has been required to incorporate some additional hardware and software components such as parallel port data bus interface, control bits decoder, driver software and acquisition software to realize this ADC. The data acquisition software has been developed under the Visual Basic (VB) programming language environment. The driver software, to enable the VB of port access capability, has been obtained from the website. The main hardware component of the developed ADC is AD574 IC. The AD574 chip is a complete 12 bit successive approximation analogue to digital converter with 3-state output buffer circuitry for direct interface to a data bus. 8-bit data bus buffer is used to interface the ADC output to the parallel port data lines. The control pulses, as required by AD574, are generated by decoding the control bits C0-C3 of the control register. C5 bit of the control register is set to the proper logic value to determine the direction of data would be appeared on the data bus (D0 - D7) of the parallel port. Standard features, such as on-line acquisition, data display, data save, data retrieve, etc. options, are included in the acquisition software. (author)