binding: gps: add binding documentation

Add initial documentation for agl-service-gps service

Bug-AGL: SPEC-1245
Change-Id: I0794842da975798637f01c6e2e4b366da686b2eb
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>

1 files changed, 42 insertions, 13 deletions

diff --git a/README.md b/README.md
index 7373158..e7ee9e8 100644
--- a/README.md
+++ b/README.md
@@ -1,19 +1,48 @@
-mkdir build
-cd build
-cmake -DCMAKE_INSTALL_PREFIX=.... ..
-make
-make install
+# GPS Service
 
-# Start the binder
+## Overview
 
-```
-afb-daemon --token=x --ldpaths=. --port=5555 --rootdir=. --verbose --verbose --verbose --verbose --verbose
-```
+GPS service reports current WGS84 coordinates from GNSS devices via the gpsd application.
 
-# Environment variables
+## Verbs
 
-* AFBGPS_HOST    : hostname to connect to
-* AFBGPS_SERVICE : service to connect to (tcp port)
-* AFBGPS_ISNMEA  : 0/1 - does the frames are NMEA or not
+| Name               | Description                             | JSON Parameters                                     |
+| ------------------ |:----------------------------------------|:----------------------------------------------------|
+| subscribe          | subscribe to gps/gnss events            | *Request:* {"value": "location"}                    |
+| unsubscribe        | unsubscribe to gps/gnss events          | *Request:* {"value": "location"}                    |
+| location           | get current gps/gnss coordinates        | See **location Event JSON Response** section        |
+| record             | start/stop recording gps data           | See **Recording/Replaying Feature** section         |
 
+## Events
+
+| Name               | Description                             |
+| ------------------ |:----------------------------------------|
+| location           | event that reports gps/gnss coordinates |
+
+### location Event JSON Response
+
+| Parameter Name | Description                                                  |
+|----------------|:-------------------------------------------------------------|
+| altitude       | altitude in meters                                           |
+| latitude       | latitude in degrees                                          |
+| longitude      | longitude in degrees                                         |
+| speed          | velocity in meters per second                                |
+| track          | heading in degrees                                           |
+| timestamp      | timestamp in ISO8601 format *(example: 2018-01-25T13:15:22)* |
+
+## Recording/Replaying Feature
+
+Entering *record* mode you must send **{"state": "on"}** with the **record** verb which will have a JSON response of
+**{"filename": "gps_YYYYMMDD_hhmm.log"}** pointing to log under *app-data/agl-service-gps*
+
+Now to enter *replaying* mode you must symlink or copy a GPS dump to *app-data/agl-service-gps/recording.log* and restart
+the service. From then on out the previously recorded GPS data will loop infinitely which is useful for testing or
+demonstration purposes.
+
+## Environment variables
+
+| Name            | Description                      |
+|-----------------|:---------------------------------|
+| AFBGPS\_HOST    | hostname to connect to           |
+| AFBGPS\_SERVICE | service to connect to (tcp port) |