started DHB docs

docs/devicehandlers.rst

@@ -1,3 +1,105 @@
 Device Handlers
 ==================
 
+Device handler components rerpresent, control and monitor equipment, for example sensors or actuators of a spacecraft or the payload.
+
+Most device handlers have the same common functionality or
+requirements, which are fulfilled by implementing an certain interface:
+
+- The handler/device needs to be commandable: :cpp:class:`HasActionsIF`
+- The handler needs to communicate with the physical device via a dedicated
+  communication bus, for example SpaceWire, UART or SPI: :cpp:class:`DeviceCommunicationIF`
+- The handler has housekeeping data which has to be exposed to the operator and/or other software
+  components: :cpp:class:`HasLocalDataPoolIF`
+- The handler has configurable parameters
+- The handler has health states, for example to indicate a broken device:
+  :cpp:class:`HasHealthIF`
+- The handler has modes. For example there are the core modes `MODE_ON`, `MODE_OFF`
+  and `MODE_NORMAL` provided by the FSFW. `MODE_ON` means that a device is physically powered
+  but that it is not periodically polling data from the
+  physical device, `MODE_NORMAL` means that it is able to do that: :cpp:class`HasModesIF`
+
+The device handler base therefore provides abstractions for a lot of common
+functionality, which can potentially avoid high amounts or logic and code duplication.
+
+Template Device Handler Base File
+----------------------------------
+
+This is an example template device handler header file with all necessary
+functions implemented:
+
+.. code-block:: cpp
+
+	#ifndef __TESTDEVICEHANDLER_H_
+	#define __TESTDEVICEHANDLER_H_
+
+	#include <fsfw/devicehandlers/DeviceHandlerBase.h>
+
+	class TestDeviceHandler: DeviceHandlerBase {
+	public:
+	  TestDeviceHandler(object_id_t objectId, object_id_t comIF, CookieIF* cookie);
+	private:
+	  void doStartUp() override;
+	  void doShutDown() override;
+	  ReturnValue_t buildNormalDeviceCommand(DeviceCommandId_t* id) override;
+	  ReturnValue_t buildTransitionDeviceCommand(DeviceCommandId_t* id) override;
+	  void fillCommandAndReplyMap() override;
+	  ReturnValue_t buildCommandFromCommand(DeviceCommandId_t deviceCommand, const uint8_t* commandData,
+	                                        size_t commandDataLen) override;
+	  ReturnValue_t scanForReply(const uint8_t* start, size_t remainingSize, DeviceCommandId_t* foundId,
+	                             size_t* foundLen) override;
+	  ReturnValue_t interpretDeviceReply(DeviceCommandId_t id, const uint8_t* packet) override;
+	  uint32_t getTransitionDelayMs(Mode_t modeFrom, Mode_t modeTo) override;
+	  ReturnValue_t initializeLocalDataPool(localpool::DataPool& localDataPoolMap,
+	                                        LocalDataPoolManager& poolManager) override;
+
+	};
+
+	#endif /* __TESTDEVICEHANDLER_H_ */
+
+and the respective source file with sensible default return values:
+
+.. code-block:: cpp
+	#include "TestDeviceHandler.h"
+
+	TestDeviceHandler::TestDeviceHandler(object_id_t objectId, object_id_t comIF, CookieIF* cookie)
+	    : DeviceHandlerBase(objectId, comIF, cookie) {}
+
+	void TestDeviceHandler::doStartUp() {}
+
+	void TestDeviceHandler::doShutDown() {}
+
+	ReturnValue_t TestDeviceHandler::buildNormalDeviceCommand(DeviceCommandId_t* id) {
+	  return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	ReturnValue_t TestDeviceHandler::buildTransitionDeviceCommand(DeviceCommandId_t* id) {
+	  return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	void TestDeviceHandler::fillCommandAndReplyMap() {}
+
+	ReturnValue_t TestDeviceHandler::buildCommandFromCommand(DeviceCommandId_t deviceCommand,
+	                                                         const uint8_t* commandData,
+	                                                         size_t commandDataLen) {
+	  return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	ReturnValue_t TestDeviceHandler::scanForReply(const uint8_t* start, size_t remainingSize,
+	                                              DeviceCommandId_t* foundId, size_t* foundLen) {
+	  return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	ReturnValue_t TestDeviceHandler::interpretDeviceReply(DeviceCommandId_t id,
+	                                                      const uint8_t* packet) {
+	  return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	uint32_t TestDeviceHandler::getTransitionDelayMs(Mode_t modeFrom, Mode_t modeTo) {
+	  return 10000;
+	}
+
+	ReturnValue_t TestDeviceHandler::initializeLocalDataPool(localpool::DataPool& localDataPoolMap,
+	                                                         LocalDataPoolManager& poolManager) {
+	  return HasReturnvaluesIF::RETURN_OK;
+	}