Change, clean plugins.

Improve GPS plugin to be able to calculate the heading also remove
the builtin plugin that was an error. We need to pass GPS plugin in
C++ to be able to use the context.

Handle "double" and "int" signal's value.

Change-Id: I6d902e4ac76a0e933326c0b4c43922645c9c5a4c
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>

1 files changed, 12 insertions, 4 deletions

diff --git a/docs/part-1/3-Plugins.md b/docs/part-1/3-Plugins.md
index 50ece7b..b58bbad 100644
--- a/docs/part-1/3-Plugins.md
+++ b/docs/part-1/3-Plugins.md
@@ -1,15 +1,23 @@
 # Plugins
 
-Plugins are C/C++ shared library loaded by the binding to execute some
+Plugins are C/C++ shared libraries loaded by the binding to execute some
 simple routine. Routine could be on reception of a new signal or at sources
 initialization time or signal subscription with the respective JSON field
-**onReceived**, **init** and **getSignals**.
+`onReceived` `init` and `getSignals`
 
 A default plugin (builtin) is provided with 2 functions:
 
 - **defaultOnReceived**: set and record a new signal value and its timestamp
  in the signal composer service. It simply tooks the incoming event JSON object
- and search for *key* **value** and **timestamp** then call function
+ and search for *key* `value` and `timestamp` then call function
  `setSignalValue`.
-- **setSignalValueWrap**: a **lua2c** function the could be called from any LUA
+- **setSignalValueWrap**: a `lua2c` function the could be called from any LUA
  script to record a new signal value.
+
+> **CAUTION**: `timestamp` value has to be typed as *uint64_t* with
+> a **nanosecond** precision using a realtime clock. To correctly store it in
+> a JSON-C object use the int64 type with the according fonctions:
+> *json_object_new_int64()*
+> *json_object_get_int64()*
+> *json_object_set_int64()*
+> *...*