extended documentation for OCPP module

Signed-off-by: pietfried <pietgoempel@gmail.com>

modules/OCPP/doc.rst

@@ -38,13 +38,20 @@ OCPP1.6 defines the SmartCharging feature profile to allow the CSMS to control o
 This module integrates the composite schedule(s) within EVerests energy management. For further information about smart charging and the
 composite schedule calculation please refer to the OCPP1.6 specification.
 
-The integration of the composite schedules are turned out by the optional requirement(s) `evse_manager_energy_sink` of this module.
-Depending on the number of EVSEs configured, each composite limit is communicated via a seperate sink, including the composite schedule
+The integration of the composite schedules are turned out by the optional requirement(s) `evse_manager_energy_sink`(interface: `external_energy_limits`) 
+of this module. Depending on the number of EVSEs configured, each composite limit is communicated via a seperate sink, including the composite schedule
 for EVSE with id 0 (representing the whole charging station). The easiest way to explain this is with an example. If your charging station
-has two EVSEs you need to connect three modules that implement the `evse_manager_energy_sink` interface: One representing evse id 0 and 
+has two EVSEs you need to connect three modules that implement the `external_energy_limits` interface: One representing evse id 0 and 
 two representing your actual EVSEs. Note that it is important to specify the connections in the EVerest config file in the correct order
 (0,1,2).
 
+This module defines a callback that gets executed every time charging profiles are changed, added or removed by the CSMS. The callback retrieves
+the composite schedules for all EVSEs (including evse id 0) and calls the `set_external_limits` command of the respective requirement that implements
+the `external_energy_limits` interface. In addition, the config parameter `PublishChargingScheduleIntervalS` defines a periodic interval to retrieve
+the composite schedule also in case no charging profiles have been changed. The configuration paramater `PublishChargingScheduleDurationS` defines 
+the duration in seconds of the requested composite schedules starting now. The value configured for `PublishChargingScheduleDurationS` shall be greater
+than the value configured for `PublishChargingScheduleIntervalS` because otherwise time periods could be missed by the application.
+
 Interaction with EVSE Manager
 =============================