Embedded Audio Engineer: Software Echo Cancellation & Clock Sync (Raspberry Pi 4)

Project Overview We are developing a battery-less, custom-powered mobile robot driven by a Raspberry Pi 4 (running Linux). The robot uses a localized audio playback system (3.5mm analog output jack) and a ReSpeaker XVF3800 4-microphone linear array connected via USB for voice command capture. We require an experienced Embedded Audio / Digital Signal Processing (DSP) Engineer to resolve a critical clock synchronization issue and implement a robust software-based Acoustic Echo Cancellation (AEC) pipeline. The Core Technical Challenge Our speaker output and microphone input are operating on entirely separate hardware clocks (the Pi's internal audio clock vs. the XVF3800's independent USB clock). This structural setup causes continuous clock drift (sample rate mismatch), causing our standard software AEC filters to diverge and fail within seconds. Because this hardware resides inside a custom robot enclosure, the speaker and microphone array cannot be wired together directly. You must resolve the clock mismatch and implement echo cancellation purely through the Linux software/firmware layers on the Pi.