Home Projects RTU-4 Modules RTU-401 Remote Telemetry Unit

RTU-401 Remote Telemetry Unit PDF Print E-mail

The RTU-401 module is a small remote telemetry unit designed for general purpose home control applications. Communications uses RS422 multidrop serial and allows up to 16 of them to share a serial line. The I/O consists of 8 opto-coupled digital inputs, 8 open-collector digital outputs (to drive relays etc) and 4 10-bit analogue inputs. It is based on a PIC16F877 device operating at 20MHz and runs from a 9-24V AC/DC supply. There's also an on-board temperature and incoming supply measurement.

Circuits and PCB details are available in the accompanying pdf files.

Expansion headers are provided for additional I/O and functionality to be added as required.

The communications protocol is a simple ascii-text based, self-synchronising, poll-response protocol that can be tested using a serial converter (RS232-RS422) and a terminal program. The accompanying protocol document describes this in detail.

RTU-401 Circuit (pdf)

RTU-401 PCB (pdf)

RTU-401 firmware 1.6 (zip)

RTU-4 protocol (pdf)

 

 
The on-board ISCP header allows for microcontroller flash in-circuit programming of firmware using a number of programmers, including the Microchip system. The complete firmware is contained in the accompanying zip file and is written in assembler using the microchip MPLAB tools.

Certain configuration information is contained in the EEPROM (eg serial number, RTU address etc) and can be adjusted during compilation of the firmware or can be modified using the serial protocol once the unit is powered up and running.