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:
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.