Five Shades of Grey: Exploring Quintary m-Sequences for More User-Friendly c-VEP-Based BCIs

Figure 2

Generic linear-feedback shift register (LFSR). For the generation of a p-ary m-sequence of order N, the register consists of memory cells , , each holding a p-ary digit. The cells are controlled by a timing clock. At each pulse of the clock, the current values of the register cells are shifted to the next cell. To determine the next value in the leftmost register cell , the current register values are multiplied by weights and then added together using modulo p arithmetics. The current value in the rightmost register cell is appended to the output sequence.