In this paper we present a sub-system to convert
audio information from low-power MEMS microphones with
pulse density modulation (PDM) output into rate coded spike
streams. These spikes represent the input signal of a Neuromorphic
Auditory Sensor (NAS), which is implemented with Spike
Signal Processing (SSP) building blocks. For this conversion, we
have designed a HDL component for FPGA able to interface
with PDM microphones and converts their pulses to temporal
distributed spikes following a pulse frequency modulation (PFM)
scheme with an accurate configurable Inter-Spike-Interval. The
new FPGA component has been tested in two scenarios, first as a
stand-alone circuit for its characterization, and then it has been
integrated with a full NAS design to verify its behavior. This
PDM interface demands less than 1% of a Spartan 6 FPGA
resources and has a power consumption below 5mW.Ministerio de Economía y Competitividad TEC2016-77785-