Double-sampling Gray TDC with a ROS Interface for a LiDAR System

This paper presents a TDC architecture based on a gray code oscillator with a ROS Interface for a LiDAR sensor. The proposed architecture introduces a double-sampling stage that takes advantage of the delay introduced by the routing between the combinatorial stage and the sampling stage. Compared to similar gray code oscillator architectures, this work significantly improves resolution and precision while maintaining good linearity and low resource utilization. Due to its portability and scalability, multiple TDC channels may be implemented by replicating a channel's placement and routing, avoiding the need for calibration methods, consequently saving resources and power. A ROS interface allows the IP to be easily integrated with other systems requiring precise and high-resolution ToF measurement. The tests performed simulating a point cloud with 36000 points showed, in the worst-case scenario, a system performance with an average of 10.32 FPS. A Zynq Ultrascale+ MPSoC was used for the TDC architecture implementation, achieving a 69 ps RMS resolution and a 59 ps single-shot precision with only 7 LUTs and 20 flip-flops. The architecture linearity reaches a peak-to-peak DNL and INL of 1.76 LSB and 1.50 LSB, respectively.