CLIENT

Private person

OVERVIEW

The being developed electronice device is supposed to become a bridge between two typically presented in every data acquisition system parts:

  • from one side: commercial power consumption monitoring and accounting system
  • from another side: electricity meter device itself

The monitoring and accounting is supposed to use widely spread Modbus RTU protocol to communicate with a set of slave devices - electricity meters. In our particular case the electricity meter Mercury 230 doesn't fully support the Modbus RTU protocol. For example, it's impossible to perform a remote autorization in meter via canonical Modbus RTU. In fact the purpose of being described device - to convert transactions to/from hi-level accounting 100%-Modbus RTU system to make it possible to gather all required information from a set of remote electricity meters with using only of Modbus RTU.

The device block diagram is shown below:

It can be seen from the diagram that the device is supposed to supply the electricity meter that it's connecting to with halvanic isolated power source 5 V @ 500 mA along with data exchange using physical RS485 interface.

The full TODO list is presented below:

  • the future device's schematics design according to sounded requirements;
  • PCB-topology design according to whole device's body size limits;
  • firmware development for device's key part - MCU;

SOLUTION

As before the development of both schematics and PCB-topology was performed with extensive usage of open-source KiCAD EDA suite. Here you may see the 3D-render of the PCB of some intermediate design revision:

MB Adapter render

The firmware development for STM32F4 series MCU was performed with Eclipse + GDB + OpenOCD bunch. The firmware itself relies on the following pieces of software:

  • STM32F4 HAL Library
  • FreeRTOS  -
  • FreeMODBUS - library written in pure C that implements Modbus RTU slave device behaviour;
  • private library that was designed during active phase of this project. It implements Modbus RTU master device behaviour;

As in almost every project before both Git version control and Doxygen source codes self-documentation system were used.

RESULTS

As of autumn 2018 the device is being tested by the Client in real situations.

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