Macros to define and control Haidenhein encoders
  as pseudomotors
  These hdh are assumed to be controlled through
  a serial line
  Through an Hdh, we can access 2 values.

  Serial line protocol:
       ^B  to ask for a value
       The response of the serial line is :
       X=`sign'    <floating value> R <CR><LF>
       Y=`sign'    <floating value> R <CR><LF><LF><LF><LF><LF>



  March 1st 1994  MCD

  NOTE: For the following macros, the HDH_DEV_index
        represents the index 0..n in the list of 
        HDH devices defined by the user with hdhsetup
        If this parameter is omitted, as it is always
        the last parameter in the list of the macro,
        Spec will replace it by 0. So omitting it
        allows to work with the first HDH of the list.

  hdhsetup nb dev_name mne cha dev_name mne cha ...

     setup of the devices

  hdh_flush  HDH_DEV_index

     print what is on the serial line buffer for one device

  hdh_read n  HDH_DEV_index

      prints the position in channel `n' (1 or 2 or 0=both)
      of one device

  hdh_read3  mne  n  HDH_DEV_index 
 
      for pseudo motor mecanism, reads the value
      of one pseudo motor
      It puts also the result in HDH_VAL

  Macros:


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  hdhsetup nb dev_name1 pseudo_mne1 ch1 dev_name2 ch22 pseudo_mne2 ...

           `nb          : nb of hdh pseudomotors defined
           Dev_name`i'  : Name of the MAXE device containing
                          the CC133 encoder for the `i'th pseudom.
           pseudo_mne`i': mnemonic associated to that pseudomotor
           ch`i'        : channel number (1 for X) or (2 for Y)
 
  when called without arguments, this macro asks interactively
  for the values

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