Circuit Lake

This project shows how to create a Renesas M16C62P-based small Remote Terminal Unit (RTU) that implements a Host communication protocol (MODBUS RTU), a smart instrumentation communication protocol Highway Addressable Remote Transducer (HART) and few digital and analog inputs and outputs.

Remote Terminal Units (RTU) are frequently used for process control and monitoring. The market for low power feature rich RTUs is increasing every day. Situations like tsunami makes of very high importance the installation of early warning systems, which is basically a low power RTU with power supplied by solar cells and small batteries. Also for other uses like oil extraction, water distribution there’s a big need of small, low power, RTUs.

One of the things that makes expensive the HART interfaces is that multiple integrated circuits are needed to implement it (Microcontroller, UART, Modem, analog front end). The rich peripheral set of the Renesas M16C62P makes possible to handle almost all these devices internally.

In this project, Inaki Zuloaga Izaguirre has designed and shown how to create a HART interface only by adding an OP AMP and a comparator (both on the same chip). Only with this interface the project is cost effective and proves that the M16C62P microcontroller can substitute previous designs where multiple chips were used. For example is perfectly viable to use this interface on: Smart Instrumentation (The same analog inputs on the M16C62P can be used to measure the field parameters and then output the values using the HART protocol), HART networks handheld configurators and protocol translation devices.