Analysis of Direct Sensor-to-Embedded Systems Interfacing: A Comparison of Targets' Performance

This paper is concerned with the direct interfacing of resistive sensors to different embedded targets. The author uses the idea of "direct sensor-to-microcontroller" technique where analog sensors are interfaced directly to inherently digital controllers and we compare the performance of this technique when applied to a typical microcontroller PIC18, a CPLD and an FPGA. Experimental results show that 5 V systems, like the PIC18 controller, have an advantage over 3.3 V systems in terms of better precision performance, while the CPLD outperforms both the microcontroller and the FPGA in terms of accuracy. The accuracy depends mainly on the output impedance of the system's I/O ports and the precision depends mainly on trigger level noise. The PIC18 controller also has the best performance in terms of linearity and sensitivity. A lot of works have been published concerning direct interfacing to microcontrollers, but little attention has been paid to alternative targets like CPLD and FPGA. This work will benchmark these different kinds of targets and prove that the direct interfacing technique can also be applied to CPLDs and FPGAs.