The change includes some labels in pre previous referred chapters,
some clarifications in the referred images, some glossary entries,
two online datasheets in the bibliography and block diagram
of a proposed client node schematic circuitry.
@ -80,3 +80,20 @@ Where there are at least two nodes in a system, they have to communicate togethe
The measuring devices, from now on called \textbf{client nodes}, will consist of blocks of the remaining hardware requirements. The resulting block diagram can be seen in the figure \ref{f:client_node})
\subsection{Hardware components breakdown}
For the \textbf{server node}, a complete working solution already exists, ready to be employed. The \textbf{GL.inet board}, described in more detail in the chapter \ref{s:glinet}, is greatly sufficient in all required aspects, and thus should be used for this purpose.
Luckily, a particular part of the required functionality for the client is already integrated as a \textbf{ESP-8266 module}, described in more detail in the chapter \ref{s:esp8266}. The module contains the TCP/IP stack, micro-controller (application processor) running the user program, \gls{wlan} and light indication, all in one piece, so this greatly simplifies the design process and allows for more focus on the actual measurement circuitry. The actual ESP-12E module should be used, because of the available certification, which allows it to be introduced on the market later. It was shown in the figure \ref{f:esp-12e}.
Talking about the measurement circuitry, the viable candidate is MAX78615 \cite{online:MAX78615} with the companion \gls{ic} MAX78700 \cite{online:MAX78700}. The couple \ref{f:schem_block} should be used, because it provides multiple ways of same voltage level communication with the processor, galvanic isolation via the pulse transformer for improved circuitry protection, great precision, accuracy and utility. The shunt resistor is utilised as a way of obtaining measurements, described in the sub-chapter \ref{ss:pmic}.
\caption{The proposed block diagram of a schematic of a \textit{client node} focusing on measuring part of the circuit}\label{f:schem_block}
\end{figure}
For the protection against fire a standard electric fuse or self-regenerative fuse should be used. The circuit protection against high voltage should be solved with an isolated DC-to-DC converter or with the linear transformer coupled with the linear voltage regulator. Since the former one is either expensive or hard to design, the choice should fall on the latter.
The remaining parts of the client node block diagram \ref{f:client_node} not yet mentioned are switching and sound indication. Either a mechanical relay or a semiconductor device, such as a thyristor or a \gls{ssr} isolated by an opto-coupler will do. Mechanical relays tend to be larger and produce sound noise, have slow response time, but have inbuilt separate isolation and are capable of switching higher currents without additional thermal issues than their semiconductor counterparts. The disadvantages of the mechanical relay are not relevant here, thus the choice is obvious.
Although it is possible to construct a circuit out of discrete components that would measure \cite{webster2003electrical} the required physical quantities, and such a solution would probably be the cheapest solution out there, it would be highly impractical due to multiple reasons.
@ -225,7 +224,7 @@ The \gls{kernel} is the essential center of a \gls{computer} \gls{os}, the core
The simplified view on the \Gls{linux}\gls{system} structure can be seen on \ref{f:linuxbl}. It does not include device \gls{driver}, \glspl{compiler}, \glspl{daemon}, \glspl{utility}, \glspl{command}, \gls{library} files and such, but should be enough for a demonstration.
\subsection{OpenWRT}
\subsection{OpenWRT}\label{ss:openwrt}
OpenWrt is an \gls{os} (in particular, an embedded \gls{os}) based on the \Gls{linux}\gls{kernel}, primarily used on embedded devices to route \gls{network} traffic. It has been optimized for size, to be small enough for fitting into the limited storage and memory available in home \glspl{router}.
OpenWrt is configured using a command-line \gls{interface} (ash \gls{shell}), or a web \gls{interface} (LuCI). There are about 3500 optional \gls{sw} packages available for installation via the \texttt{opkg} package management \gls{system}.
@ -241,7 +240,7 @@ The main components are the \Gls{linux} \gls{kernel}, \texttt{util-linux-ng}, \t
\newpage
\section{GL.inet board}
\section{GL.inet board}\label{s:glinet}
GL.inet Smart \Gls{router} is a remake of a common TP-Link \gls{router} TL-WR703N. The board changes include, but are not limited to, increased \gls{ram} and \Gls{flash} memory, custom \gls{firmware} and what is the most important - 5 usable \gls{gpio} pins exposed to the 2cm pin header for utility. Whole thesis is revolving around taking advantage of this fact. The frequency of \gls{cpu} is 400 \gls{mhz} and it is suited for running \Gls{linux} distributions for embedded devices, preferably OpenWrt or DD-Wrt. The board provides \gls{lan} and \gls{wan} connection, as well as other \glspl{interface} defined in \gls{ieee}. The information about the board are summed up in the table \ref{t:charact}.
\begin{table}[h]
@ -320,13 +319,13 @@ Whole printed circuit board of TL-WR703N was remade by the GL.inet team to expos
\newpage
\section{ESP8266 Wi-Fi module}
\section{ESP8266 Wi-Fi module}\label{s:esp8266}
The ESP8266 Wi-Fi module is a self contained \gls{soc} with integrated \gls{tcpip} protocol stack that can give any microcontroller access to your Wi-Fi network. The ESP8266 is capable of either hosting an application or offloading all Wi-Fi networking functions from another application processor. The ESP8266 module is an extremely cost effective solution, with a huge code-base and community, making it a preferable option for many modern projects, mainly the ones that follow the \gls{iot} trend.
\caption{The first commercial iteration of the ESP8266 module, exposing two \glspl{gpio}}\label{f:esp-01}
\caption{The first commercial iteration of the ESP8266 module, the ESP-1, exposing two \glspl{gpio}}\label{f:esp-01}
\end{figure}
This module has a powerful enough on-board processing and storage capability that allows it to be integrated with the sensors and other application specific devices through its \glspl{gpio} with minimal development up-front and minimal loading during runtime. Its high degree of on-chip integration allows for minimal external circuitry, including the front-end module, is designed to occupy minimal \gls{pcb} area.
@ -334,7 +333,7 @@ This module has a powerful enough on-board processing and storage capability tha
Peter Babič
8 years ago