A Simple Driver Example

In this simple example the programmer does not need to define action scripts. The needed scripts are already in stdsct.tcl.

Before presenting the driver, we look at the command we need in the configuration file for any device using this driver:

makenv tem ls336

or, if for some reason you want to give the name of the controller explicitly,

makenv tem ls336 _tem

This command looks if the driver script ~/sea/tcl/drivers/ls336.tcl exists, if not, it tries to look for a driver of an older type. It remembers the object name (tem) and the controller name (_tem). If no controller name is given an underscore character is prepended to the object name to set the controller name.

Now we look at the driver file ~/sea/tcl/drivers/ls336.tcl:

namespace eval ls336 {} {
}

proc stdConfig::ls335 {} {

  controller std sendterminator=\r timeout=5
  controllerDesc "LakeShore 336 controller"
  prop startcmd "*IDN?"

  obj LS336 -float rd
  prop readcmd "KRDG?A"
  prop readfmt "%g"

  kids "LS336 settings" {
    node set -float wr
    prop readcmd "SETP?1"
    prop readfmt "%g"
    prop writecmd "SETP 1,%g"

  }
}

Explanation, line by line

controller std sendterminator=\r timeout=5

The controller object is defined with the name specified in the makenv command, specifying the characteristics of the protocol.

controllerDesc "LakeShore 336 controller"

A description of the controller object.

prop startcmd "*IDN?"

The command prop creates a property to the last defined node, which is in this case the controller node. The property startcmd defines a command which is sent after initialization. Ideally this is a command requesting the instrument type, software version number and possibly a serial number. After an interruption of the connection, this command is sent again in order to check that the device is still the same.

obj LS336 -float rd

This creates the object with the name specified in the makenv command. Its value is a float, and it is a rd node, which means, it is a value read from the hardware device at regular intervals, by default every 5 seconds. It is read only.

prop readcmd "KRDG?A"

We define a property of the object node: readcmd. This is the command to be sent to get the value, in this case the temperature of channel A.

prop readfmt "%g"

This is the format for converting the result to a floatin gpoint value. In this case it is a normal floating point value. For