A bidirectional hub for a programmable gain/filtering data acquisition of a low interference electroencephalogram

This article presents the implementation of an Electroencephalogram - EEG system less susceptible to electromagnetic interference - EMI. The amplification, filtering and A/D conversion are placed directly over each electrode. Due to the local amplification and conversion, the system becomes more resilient to EMI and consequently the results are trustier. It was developed a central chip or hub that collects data of all electrodes and send it wireless to an external computer or a registering device. Since the amplification and filtering are adjustable, the hub also receives the amplification/filtering parameters from the computer and sends them to the circuits over the electrodes. The amplification/filtering adjustment improves the signal quality since electrode is properly adjusted. This article describes the protocol and circuitry of the bidirectional communication between the hub and the electrodes. The circuit was developed in Verilog and validated on a set of FPGAs, where one FPGA works as a hub and the others work as electrodes. The results show the system works properly. The amplification/filtering is individually adjusted, thus providing great flexibility to the system.