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choco.w
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choco.w
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\subsection{Chopper Controller}
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Yet another way to deal with a controller has beenn devised for
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SICS. This uses the concept of a general controller which can have
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parameters enquired and set. Furthermore it may have parameters which
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may be driven like a motor through a special adapter. This scheme is
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used for the chopper controller for FOCUS.
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\begin{itemize}
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\item A driver for a particular controller which allows to set and get
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parameters.
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\item The general controller object which holds things together.
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\item An adapter object which allows to drive special parameters in a general
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controller. Such adapter objects can be configured for each drivable parameter
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in a controller.
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\end{itemize}
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The test case for this way of doing things is a controller for running
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choppers. This is why it gets the name.
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The chopper system in question is the FOCUS chopper system. There are two
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choppers, a fermi chopper and a disk chopper. This system can be run in two
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different modes: In synchronous mode both choppers run at a
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predefined ratio of speeds. For instance the fermi chopper is two
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times faster then the disk chopper. This means, that setting a new
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value for one chopper also changes the speed of the other chopper. In
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asynchronous mode both choppers operate independently. Also the ration
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to use for synchronous mode can be changed. Another parameter which
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frequently changes is the phase of the two choppers. In order to
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compensate for the fligh path between the two choppers there is a
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small angular displacement of the choppers against each other which
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varies with wavelength.
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\subsubsection{The Controller Driver}
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The controller driver is represented by the following data structure:
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@d codri @{
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typedef struct __CODRI *pCodri;
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typedef struct __CODRI {
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int (*Init)(pCodri self);
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int (*Close)(pCodri self);
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int (*Delete)(pCodri self);
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int (*SetPar)(pCodri self,
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char *parname,
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float fValue);
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int (*SetPar2)(pCodri self,
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char *parname,
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char *value);
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int (*GetPar)(pCodri self,
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char *parname,
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char *pBuffer,
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int iBufLen);
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int (*CheckPar)(pCodri self,
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char *parname);
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int (*GetError)(pCodri self, int *iCode,
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char *pError,
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int iErrLen);
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int (*TryFixIt)(pCodri self, int iCode);
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int (*Halt)(pCodri self);
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char *pParList;
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void *pPrivate;
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}Codri;
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@}
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All functions take a pointer to the controller driver itself as a
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parameter. All functions except TryFixIt and CheckPar
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return 0 on failure and 1 for success.
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\begin{description}
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\item[Init] initializes the controller driver. The parameters argc,
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argv are main() style parameters for the initialization of the
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controller driver.
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\item[Close] closes the connection to the controller but does not delete a thing.
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\item[Delete] closes the connection to the controller and deletes private data structures. Called when deleting the controller.
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\item[SetPar] tries to set the parameter parname to the value
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fValue. The last is floating point which covers the frequent
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occurence of numeric values.
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\item[SetPar2] The same as SetPar but uses test string as input for
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parameter setting.
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\item[GetPar] retrieves the parameter parname formatted as test. The
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value is put into the buffer pBuffer. iBufLen is the maximum number of
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bytes permissable for pBuffer.
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\item[CheckPar] When parameters are driven a means is needed to find
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out about the progress of operations and errors during the
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operation. This is done by CheckPar for the parameter parname. The
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return value of this function must be one of the HWBusy, HWError,
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HWDone family documented in the motor driver object description.
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\item[GetError] retrieves the last error. An integer error code is
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placed into iCode and a textual description of the problem is written
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to pError. Maximum iErrLen bytes are copied to pError.
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\item[TryFixIt] tries to fix the error condition specified by iCode in
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software if this possible. TryFisIt returns HWRedo if the last command
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needs to resent, HWFault if the problem could not be fixed and HWOK if
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the error can be ignored or was fully resolved.
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\item[pParList] is text string containing a comma separated list of
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all parameters understood by this driver.
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\item[pPrivate] Is a pointer to a driver specific specific data
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structure. This data structure will not be messed with by upper level code.
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\end{description}
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\subsubsection{The Controller Object}
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This is the general controller object visible from the SICS
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interpreter. This object allows to list all possible
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parameters. Internal functions are provided for setting
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parameters. But this is meant to be operated through a drive adapter
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object (see below) in SICS. Thus the interface to this object
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includes:
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@d chocoint @{
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typedef struct __CHOCO *pChoco;
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/*------------------------------------------------------------------------*/
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int CHGetParameter(pChoco self, char *pParName,
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char *pParValue, int iBuflen);
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pCodri CHGetDriver(pChoco self);
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int CHList(pChoco self, SConnection *pCon, char *name);
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/*------------------------------------------------------------------------*/
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int ChocoAction(SConnection *pCon, SicsInterp *pSics, void *pData,
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int argc, char *argv[]);
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int ChocoFactory(SConnection *pCon, SicsInterp *pSics, void *pData,
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int argc, char *argv[]);
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@}
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\begin{description}
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\item[CHGetParameter] retrieves the value of the parameter ParName
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converted to text. Maximum iBufLen of result or error text are copied into the
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buffer pParvalue.
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\item[CHGetDriver] returns a pointer to the controller driver. This
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function will be used by the drive adapters for interfacing with the
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driver directly.
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\item[CHList] prints a listing of all parameters to the client
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described by pCon. name is the name of the controller.
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\item[ChocoAction] is the SICS interpreter interface function for the
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controller.
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\item[ChocoFactory] is the SICS interpreter interface function which
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installs a controller into SICS.
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\end{description}
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Most of the actual work of the controller is left to the driver. Thus
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the internal data structure for a controller object is very simple:
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@d chocodata @{
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typedef struct __CHOCO {
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pObjectDescriptor pDes;
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pCodri pDriv;
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} Choco;
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@}
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It consists just of the standard SICS object descriptor and a pointer
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to the driver.
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\subsubsection{The Drive Adapter}
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Most of the work of the drive adaptor is hidden in the functions
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implementing the drivable interface. Thus the interface to the
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DriveAdapter is fairly simple:
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@d adapter @{
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typedef struct __CHADAPTER *pCHAdapter;
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/*-----------------------------------------------------------------------*/
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int CHAdapterFactory(SConnection *pCon, SicsInterp *pSics,
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void *pData,
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int argc, char *argv[]);
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int CHAdapterAction(SConnection *pCon, SicsInterp *pSics,
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void *pData,
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int argc, char *argv[]);
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@}
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\begin{description}
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\item[CHAdapterFactory] is the SICS interpreter factory function for
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creating a drive adapter.
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\item[CHAdapterAction] is the SICS interpreter function for
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representing the object in SICS. Just a single action is supported:
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request the value of the parameter.
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\end{description}
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The data structure for the drive adapter is slightly more interesting:
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@d adadata @{
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typedef struct __CHADAPTER {
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pObjectDescriptor pDes;
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pCodri pDriv;
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pIDrivable pInt;
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float fUpper;
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float fLower;
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float fTarget;
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char *pParName;
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}CHAdapter;
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@}
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\begin{description}
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\item[pDes] is the standard object descriptor.
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\item[pDriv] is a pointer to the controller driver.
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\item[pInt] is a pointer to the drivable interface implemented by the
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adapter.
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\item[fUpper] upper limit for the parameter.
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\item[fLower] lower limit for the parameter.
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\item[pParName] is the name of the parameter which is driven through
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this adapter.
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\end{description}
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@o codri.h @{
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/*-------------------------------------------------------------------------
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C o n t r o l l e r D r i v e r
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This file contains the description of the data structure for a
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general controller driver.
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Mark Koennecke, January 1998
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--------------------------------------------------------------------------*/
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#ifndef CODRIV
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#define CODRIV
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#define CHFAIL -1
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#define CHREDO -2
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#define CHOK -3
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@<codri@>
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#endif
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@}
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@o choco.h @{
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/*-----------------------------------------------------------------------
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C h o p p e r C o n t r o l l e r
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This is both the header file for a general controller and a SICS
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chopper controller.
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Mark Koennecke, January 1998
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--------------------------------------------------------------------------*/
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#ifndef CHOCOSICS
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#define CHOCOSICS
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#include "codri.h"
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@<chocoint@>
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#ifdef CHOCOINTERNAL
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@<chocodata@>
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#endif
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#endif
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@}
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@o chadapter.h @{
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/*------------------------------------------------------------------------
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C H a d a p t e r
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This is the header file for a drive adapter for collaboration with a
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general device controller as implemented in choco.*
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Mark Koennecke, January 1998
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--------------------------------------------------------------------------*/
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#ifndef SICSCHADA
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#define SICSCHADA
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#include "codri.h"
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@<adapter@>
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#ifdef CHADAINTERNAL
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@<adadata@>
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#endif
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#endif
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@}
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\subsubsection{To Do}
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This scheme seems to be quite promising for handling many SICS
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objects. The following enhancements could be considered. Allow to set
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certain primitive parameters without a drivable interface. And add an
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adapter for an environment variable in the controller.
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