Manchester decoder of a home thermostat's wireless protocol in the Tiny Tapeout 07 shuttle

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Abstract

This lightning talk presents the Verilog design and ASIC implementation of a Manchester-coded baseband packet decoder using the Tiny Tapeout platform. The receiver is designed to process digital baseband signals from low-cost 433 MHz OOK RF receivers (e.g., RXB6), which provide a demodulated digital output. A custom state machine performs Manchester decoding using oversampling and timer-based edge detection, eliminating the need for analog components such as PLLs. The decoder identifies preamble patterns in-stream using a 97-bit shift register and captures a 96-bit payload, which is exposed via an 8-bit parallel addressable interface. Simulation and gate-level testing was conducted using cocotb and Icarus Verilog, with test inputs derived from real-world signal captures. The design was hardened and submitted via the Tiny Tapeout flow, targeting the SkyWater SKY130 process. The final implementation fits within a single Tiny Tapeout tile, with utilization reduced from 62% to 32% through logic simplifications. Critical paths were optimized by applying ASIC design best-practices: avoiding unnecessary flip-flops, and asynchronous reset logic. This work demonstrates a practical, low-barrier path to ASIC design for digital communication decoders — especially for baseband-only, low-data-rate applications.

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