diff --git a/documentation/Morse_reception_state_diagram.tex b/documentation/Morse_reception_state_diagram.tex
new file mode 100644
index 0000000..fde396c
--- /dev/null
+++ b/documentation/Morse_reception_state_diagram.tex
@@ -0,0 +1,70 @@
+\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}
diff --git a/main.py b/main.py
index d48ef9f..0908549 100644
--- a/main.py
+++ b/main.py
@@ -14,6 +14,9 @@ rtc.setDate(16, 7, 2022)
 rtc.setTime(12, 10, 0)
 rate = 50 # 20 wpm
 
+# 0=IDLE 1=KEYDN 2=DIT 3=DAH 4=SPACE
+morse_state = 0
+
 #sec = 0
 #f = open(logFileName, 'a')
 #f.write("# Data Logging: Date, Time, Temperature, Pressure, Humidity, AirQuality, CO2\n")
@@ -41,7 +44,7 @@ def ButtonA_f_IRQHandler(pin):
     print (" IRQ button A" + str(rate))
     
 def ButtonB_f_IRQHandler(pin):
-    global last_pv, last_tt, spurious, mindex
+    global last_pv, last_tt, spurious, mindex, morse_state
     pv = pin.value()
     tt  = time.ticks_ms()
     #print("button B IRQ", tt, pv)
@@ -51,7 +54,12 @@ def ButtonB_f_IRQHandler(pin):
     else:
         #b=buttonEvent(time.ticks_ms(),pv)
         d = tt - last_tt
-        if pv:
+        if pv: # MORSE BUTTON DOWN
+            
+            if ( morse_state == 4 ):
+              if d > rate*7:
+                 printm(' ')
+                
             #print(" duration of inter-m space ", d)
             if d < rate*3:
                 print (" ")
@@ -60,14 +68,17 @@ def ButtonB_f_IRQHandler(pin):
                 mindex += 1;
             beeper.playTone(600)
             button_state = 1
-        else:
+            morse_state = 1 # button down
+        else: # MORSE BUTTON RELEASED
             #print(" duration of press ", d)
             if d > rate*3:
                 morse.append("-");
-                print ("DAH")
+                #print ("DAH ms=", morse_state)
+                morse_state = 3
             else:
                 morse.append(".");
-                print ("DIT")
+                #print ("DIT ms=", morse_state)
+                morse_state = 2
             beeper.stopTone()
             button_state = 0
     last_pv = pv
@@ -213,27 +224,17 @@ def decode_morse():
         return ("9")       
     return("?")
         
-        
-last_was_space = 0
-last_sp = 0
-def process_morse():
-    global last_tt, morse, last_was_space, last_sp
-    tt  = time.ticks_ms()
-    if (button_state == 0):
-        if (tt - last_tt) > rate*6:
-            # morse chacter complete
-            if (len(morse) > 0):
-                #print(morse)
-                printm(decode_morse())
-                morse = []
-                last_was_space = 0
-                last_sp = last_tt
   
-        if (tt - last_sp) > rate*22 : # and last_not_space == 0:
-            if last_was_space == 0:
-                printm(" ");
-            last_was_space = 1 # dont keep repeating inter word spaces
-            last_sp = last_tt
+def process_morse():
+    global last_tt, morse, morse_state
+    tt  = time.ticks_ms()
+    if ( morse_state == 2 or morse_state == 3):
+        if (tt - last_tt) > rate*3:
+            # morse chacter complete
+            printm(decode_morse())
+            morse = [] # clear for next character to rxd
+            morse_state = 4
+