Implementation of a bidirecional serial communication protocol using shared channel

Abstract

Ultra-dense array of Electroencephalogram (EEG) may contain 256 or even 512 electrodes, which offers a challenge to provide intercommunication between each electrode and a central communication hub. This article presents a solution for communication between several electrodes and a hub, in same channel, to be implemented by a pair of wires. Since each electrode may be differently located over the scalp, and since they can perform signal amplification and filtering, they must be individually configured, and thus the communication must be bidirectional. A dedicated channel to each electrode would be unfeasible due to the large number of wiring. Thus, we have developed an asynchronous bidirectional communication protocol that allows a large number of devices in a single channel. The communication hub acts a single master and all electrodes are the slaves, but only one at a time. The protocol was implemented in Verilog and validated in a system implemented with FPGA boards.