Add section on device configuration to Esp8266 getting-started page

Should address common problems getting code to run.

docs/source/arch/esp8266/getting-started/index.rst

@@ -1,8 +1,55 @@
 Getting Started: ESP8266
 ========================
 
+Development Environment
+-----------------------
+
 .. toctree::
    :glob:
    :maxdepth: 1
 
    *
+
+Configuring your Esp8266 device
+-------------------------------
+
+.. highlight:: bash
+
+You may need to configure your project to support the specific device being programmed.
+
+.. note::
+
+   Arduino has a system which allows these values to be set based on a *board*
+   selection. At present Sming does not have such a system so this must be done
+   manually.
+
+Here are a few important ones:
+
+* :envvar:`SPI_MODE` Change this if your device fails to program or run
+* :envvar:`SPI_SIZE` If using a device with reduced memory you may need to change this value. Note also that samples using :component:`spiffs` may not work.
+* :envvar:`COM_PORT` If you haven't set this already, it will need to match the port you're using to talk to the Esp8266.
+* :envvar:`COM_SPEED_ESPTOOL` The default value should work fine but you can usually set a much faster speed.
+
+You can set these initially on the command line, like this:
+
+::
+
+   make SMING_ARCH=Esp8266 SPI_MODE=dio SPI_SIZE=4M COM_SPEED_ESPTOOL=921600
+
+Once you're happy with the settings, you can add them to your ``project.mk`` file.
+
+You can list the current set of configuration variables like this:
+
+::
+
+   make list-config
+
+If you want to reset back to default values, do this:
+
+::
+
+   make config-clean
+
+
+* See :doc:`/_inc/Sming/building` for further details about configuring your project.
+* See :doc:`/features` for configuring Sming options.

docs/source/arch/esp8266/getting-started/linux.rst

@@ -71,10 +71,14 @@ Set ENV Variables
    export ESP_HOME=/opt/esp-open-sdk
    export SMING_HOME=/opt/Sming/Sming
 
-To Sming environment paths permanently: Just go to the Sming home
-directory /opt/Sming/Sming and edit the file Makefile: because this
-library has defaults for a nutter and programmers (like myself add
-config options and never document them)
+To set these permanently, add them to your home ``.profile`` file.
+
+You can alternatively add them to ``/etc/environment`` for all users, like this:
+
+::
+
+   SMING_HOME="/opt/Sming/Sming"
+
 
 See also
 `Setting up Sming and Netbeans <https://primalcortex.wordpress.com/2015/10/08/esp8266-setting-up-sming-and-netbeans/>`__
@@ -116,7 +120,3 @@ Build and flash a ‘Basic Blink’ example (using ttyUSB0):
    cd $SMING_HOME/../samples/Basic_Blink
    make flash
 
-Configuration
-=============
-
-You might want to configure your project before building. Edit **component.mk**.