Move documentation to doc subdirectory.

Add/update README.md files.

README.md

@@ -49,7 +49,7 @@ Version 1.2 decodes more than 1000 error-free frames from [WA8LMF TNC Test CD](h
 
 ### Windows ###
 
-Go to the [releases page](releases/).   Download a zip file with "win" in its name, unzip it, and run direwolf.exe from a command window.
+Go to the [releases page](https://github.com/wb2osz/direwolf/releases).   Download a zip file with "win" in its name, unzip it, and run direwolf.exe from a command window.
 
 ### Linux - short version for the impatient ###
 

doc/README.md

@@ -0,0 +1,65 @@
+# Documentation for Dire Wolf #
+
+
+## Essential Reading ##
+ 
+- [User Guide](User-Guide.pdf)
+
+	This is your primary source of information about installation, operation, and configuration.
+
+- [Raspberry Pi APRS](Raspberry-Pi-APRS.pdf)
+
+	The Raspberry Pi has some special considerations that
+	make it different from other generic Linux systems.
+	Start here if using the Raspberry Pi, Beaglebone Black, cubieboard2, or similar single board computers.
+
+	
+## Application Notes ##
+
+These dive into more detail for specialized topics or typical usage scenarios.
+
+
+- [APRStt Implementation Notes](APRStt-Implementation-Notes.pdf)
+
+	Very few hams have portable equipment for APRS but nearly everyone has a handheld radio that can send DTMF tones.  APRStt allows a user, equipped with only DTMF (commonly known as Touch Tone) generation capability, to enter information into the global APRS data network.
+	This document explains how the APRStt concept was implemented in the Dire Wolf application.  
+
+- [APRStt Interface for SARTrack](APRStt-Interface-for-SARTrack.pdf)
+
+	This example illustrates how APRStt can be integrated with other applications such as SARTrack, APRSISCE/32, YAAC, or Xastir.  
+
+
+- [Raspberry Pi SDR IGate](Raspberry-Pi-SDR-IGate.pdf)
+
+	It's easy to build a receive-only APRS Internet Gateway (IGate) with only a Raspberry Pi and a software defined radio (RTL-SDR) dongle.  Here’s how.
+
+- [APRS Telemetry Toolkit](APRS-Telemetry-Toolkit.pdf)
+
+	Describes scripts and methods to generate telemetry.
+	Includes a complete example of attaching an analog to 
+	digital converter to a Raspberry Pi and transmitting 
+	a measured voltage.
+
+## Miscellaneous ##
+
+
+- [A Better APRS Packet Demodulator, part 1, 1200 baud](A-Better-APRS-Packet-Demodulator-Part-1-1200-baud.pdf)
+
+	Sometimes it's a little mystifying why an
+APRS / AX.25 Packet TNC will decode some signals
+and not others.  A weak signal,  buried in static,
+might be fine while a nice strong clean sounding
+signal is not decoded.  Here we will take a brief
+look at what could cause this perplexing situation
+and a couple things that can be done about it.	
+
+
+
+- [A Better APRS Packet Demodulator, part 2, 9600 baud](A-Better-APRS-Packet-Demodulator-Part-2-9600-baud.pdf)
+
+	In the first part of this series we discussed 1200 baud audio frequency shift keying (AFSK).  The mismatch 
+	between FM 	transmitter pre-emphasis and the 
+	receiver de-emphasis will 
+	cause the amplitudes of the two tones to be different.
+	This makes it more difficult to demodulate them accurately.
+	9600 baud operation is an entirely different animal.  ...