Software-Defined DDPM Modulators for D/A Conversion by General-Purpose Microcontrollers

Abstract

The software implementation of Dyadic Digital Pulse Modulators (DDPMs) for Digital to Analog (D/A) conversion is addressed in this paper. In particular, an enhanced software DDPM implementation is proposed and compared with a plain, iterative software transposition of the basic DDPM hardware architecture. Experimental results on an 8-bit software-defined DDPM D/A converter implemented on a Texas Instrument c2000 microcontroller platform validate the approach, revealing for the novel optimized software DDPM a 6X maximum sample rate compared to the simple iterative implementation on the same microcontroller and at the same system clock frequency. Based on measurements, an 8-bit DDPM DAC featuring the proposed optimized implementation operates at 7.8kS/s with a maximum INL of 1.64LSB, a maximum DNL of 1.79LSB, an SFDR of 47.02dB and a SNDR of 45.27dB, corresponding to 7.23 ENOB, demonstrating the effectiveness and the applicability of the proposed approach to implement a low cost, software-defined D/A converters in microcontroller-based embedded systems.