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EASE - An Easy Way to Write Sample Environment Drivers
Motivation
Drivers for sample environment (SE) have some special
demands which were not fully supported by the original SICS
environment controller (EVC):
- SE is changing, therefore the creation of objects is
dynamic (i.e. after startup). This was already supported,
but with the drawback, that they had to be created again
when restarting SICS. All EASE objects are dynamic
and persistent.
- As SE hardware might be changed, it is not always guaranteed,
that a device is connected and switched on. With the devices
implemented in EVC, waiting for a response blocks the SICS
server. EASE objects work with a simple "finite state machine"
(fsm.c) which simulates a parallel execution of the tasks to
be performed.
- Making an EVC driver means writing a lot of code for
initialization. For a more complex driver you need also much
parameter and subcommand handling. EASE does initialization
and parameter handling for you.
pardef
pardef.c contains the implementation base class ParData for a
new type of SICS object. It contains parameter definition, parameter
handling, parameter listing, logging and storing. The parameter definiton
function is the heart of any object based on pardef. This function
is called by the system for different actions which can be performed
on an object.
EASE
ease.c contains two classes: EaseBase inherits ParData. It
includes the finite state machine, and the handling of a serial
connection to the hardware. EaseDriv inherits EaseBase.
It makes the object driveable.
fsm
fsm.c is the implementation of a simple processor. The tasks
which can be executed are functions (FsmFunc) which contain a switch
statement, where every case is a step of the task to execute. When combined with
EASE, the individual steps normally end with a command written to
the device. After any step, the FsmFunc returns the line number
of the next step. The system calles the FsmFunc again, when the response
is ready. FsmFuncs might be nested.
Drivers based on EASE
For a driver, one needs to define
- the parameter definition function
- the start function, an FsmFunc, called after connection to the device
- the read function, called repeatedly. It should read all relevant
information from the device
- a protocol dependent handler, dealing with the specialities of
a protocol. This is normally implemented in a separate source file,
as it might be used for different devices using the same protocol.
- for driveable objects, a run function. It should contain all
operations needed to drive to the target value
- the initializer, calling EaseMakeBase or EaseMakeDriv with some class
information and the functions mentioned above as arguments
- the init function, creating the class and inserting the initializer to
the system
Common Parameters and Subcommands for all EASE Objects
Commands are marked with c in the second column, read-only parameters with r,
writeable parameters with w.
Subcommand or
Parameter | C/W/R | Action | Defined by |
|---|
| list | c | Make a list of most important parameters (all parameters defined with a call to ParTail and not ParList, or with a call to ParList(NULL) | pardef |
| list all | c | Make a full list of all parameters | pardef |
| list <group> | c | Make a list of only a group of parameters (all parameters defined with a call to ParList("<group>") ) | pardef |
| log <par> | c | Switch the logger on for parameter <par> (on for parameters defined without an explicit call to ParSwitch(NULL) ) | pardef |
| log <par> <sugar> | c | Switch the logger on for parameter <par>, giving a sugar name (see SicsStrObjSugar?) | pardef |
| unlog <par> | c | Switch the logger off for parameter <par> | pardef |
| sugar | c | Return a list of sugar parameters | pardef |
| save <par> | c | Switch on status file saving for parameter <par> (on for changeable parameters, or explicitley when defined with a call to ParSave | pardef |
| unsave <par> | c | Switch off status file saving for parameter <par> | pardef |
| interest | c | Switch interest callback on (every change will be notified to the executive client) | pardef |
| uninterest | c | Switch interest callback off | pardef |
| verbose | w | Control verbosity. 0 is quiet, 1 is standard, 2 is verbose (logging all serial communication) | ParStdDef |
| driver | r | Driver name | ParStdDef |
| creationCmd | r | command to create this object | ParStdDef |
Currently implemented drivers
Oxford Instruments Devices (protocol handler: oxinst.c)
- ilmdriv.c (based on EaseBase)
- ipsdriv.c, itcdriv.c, ighdriv.c (based in EaseDriv)
ModBus devices (protocol handler: modbus.c)
- euro2kdriv.c (based on EaseDriv)
This particular version was published on 19-Sep-2005 07:52:50 UTC by MarkusZolliker.
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