started DHB docs

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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;
}