Field programmable gate array in a fast 256-channel data acquisition system

We describe an FPGA (Field Programmable Gate Array) controlled fast data acquisition system with 256 channels suitable for high resolution electrocardiographic (ECG), electrogastrographic (EGG) and late potential (LP) recordings. The A/D converter provides 800ns conversion time with 12 bits. The S11W, a 16 bit, parallel, I/O interface, is used to connect the data acquisition device to a portable SPARC-compatible computer. With only one A/D converter, we have achieved 2 kHz sampling rate for each channel and more than 1MB/s overall by using an overlapping delay technique. Channel parameters can be selected independently from one of eight gains ranging from 50 to 10,000, and one of three filters ("ECG" 0.05-120Hz, "EGG" 0.001-1Hz and "LP" 60-1kHz). There are eight programmable sampling frequencies from 2Hz to 2kHz. The system is fully battery operated and protected from the defibrillation high voltages to meet the safety requirements. The acquisition system can be widely used in medical research and clinical applications.