\documentclass{article} % Language setting % Replace `english' with e.g. `spanish' to change the document language \usepackage[english]{babel} % Set page size and margins % Replace `letterpaper' with `a4paper' for UK/EU standard size \usepackage[letterpaper,top=2cm,bottom=2cm,left=3cm,right=3cm,marginparwidth=1.75cm]{geometry} % Useful packages \usepackage{amsmath} \usepackage{graphicx} \usepackage[colorlinks=true, allcolors=blue]{hyperref} \usepackage{tikz} \usetikzlibrary{automata, positioning, arrows} \title{Morse reception state machine} \author{R.P. Clark} \begin{document} \maketitle \begin{abstract} Your abstract. \end{abstract} \section{Introduction} State machine for morse rt decoding. \begin{itemize} \item 0: IDLE --- start state \item 1: KEY\_DN --- Morse KEY is DOWN \item 2: DIT --- Morse DIT element registered \item 3: DAH --- Morse DAH element registered \item 4: END\_CHAR --- One morse character registered i.e. (A-Z0-9) \item 5: SPACE --- One SPACE between characters registered \end{itemize} The relationships between these states is shown in figure~\ref{fig:morse_rt_reception}, the time $\tau$ is 50mS for 20 characters per minute Morse code. \begin{figure} \centering \begin{tikzpicture} \node[state, initial] (q0) at (2,12) {0:IDLE}; \node[state] (q1) at (4,9) {1:KEY\_DN}; \node[state, accepting] at (10,6) (q2) {2:DIT}; \node[state, accepting] at (8,6) (q3) {3:DAH}; \node[state, accepting] at (4,3) (q4) {4:END\_CHAR}; \node[state, accepting] at (2,0) (q5) {5:SPACE}; \draw (q0) edge[->>,right] node{key down} (q1) (q1) edge[->>,right] node{KEY\_UP $\tau \approx 1$} (q2) (q1) edge[->>,left] node{KEY\_UP $\tau \approx 3$} (q3) (q2) edge[->>,right] node{$\tau \approx 3$} (q4) (q3) edge[->>,left] node{$\tau \approx 3$} (q4) (q4) edge[->>,left] node{$\tau > 4$} (q5) (q5) edge[->>,right, bend left, left=4.3] node{key down} (q1) (q4) edge[->>,left, bend left, left=4.3] node{key down} (q1) ; \end{tikzpicture} \caption{State diagram for morse real time reception} \label{fig:morse_rt_reception} \end{figure} %\bibliographystyle{alpha} %\bibliography{sample} \end{document}