Here are my suggestions for a Common Data Aquisition API, please send
your suggestions/criticism to this list.

OK

 First we should start with the 'Atoms', we need support for the
 most popular chipsets. There should be a global info struct
 that contains informations about 'global' parameters for the
 chipset (for example a oscillator frequency used for timing}
 The 'Modes' can be controlled thru the API. Selecting one mode
 blocks the Atom for other use.

 An atom can be configured (initialized), a mode can be selected for an atom
 and operation8 can be triggered. 
 
 Each mode has its own configuration, each time a mode is selected the 
 atom cannot be used by another virtual instrument.
 Depending on what chipset type is configured the operational modes have
 different meanings (the PIO for example). An Atom can be a chipsets 
 feature (on  8255 for example there could be one atom for each port)
 
 bigger blocks of data should be transferred with read()/write() 
 preceeded by one A_CONFIGURE that switches the buffer pointer 
 to the desired atom.

 Currently I have no idea how events can be used to trigger user actions.

 I think only one Major number should be used for all atoms
 atom-addressing could be done by open one minor device per atom
 or by giving the atom address as intrinsic information with the
 call-structs (I think this method will be more flexible). 
 The chipset setup should be done from a special config 
 program that reads a hardware config-spec file.
 

 --------------------------------------------------------------------------
 Calling conventions:
      open( "/dev/atoms/xxx", O_RDWR);
         opens the desired atom. 

      ioctl(fd,A_CONFIGURE, config_s s)         
         config_s contains global information about an atom
         chipset_type, xtal frequencies etc.

      ioctl(fd,A_SELECT, mode_s s)  
         selects a operational mode for an atom


      ioctl(fd,A_TRIGGER, trigger_s s)
         triggers a hardware operation
         start/stop etc    
         
      ioctl(fd,A_STATUS, status_s *s)
         ask for status information
     
      read()/write() read or write to atoms data-buffer (if any)
      for results.

  ------------------------------------------------------------------------
  Operational Modes:


         o Counter and Timing Controllers:
           --------------------------------
             - 8253, Am9513, ...

             Global configuration:
               chipset type,
               xtal freq,

             Modes:
	       1.) Event Counter

                   One or more counter(s) can be used as event counter
                   one click per pulse

                       parameter: {preset value}
                       result: {The count}

               2.) Frequency Counter

		   One Counter is used as timebase counter triggering the
                   gate of the event counter.

			parameter: { timebase count , xtal freq }
                        result:    { the count }

               3.) Pulse Generator ( pulse freq & with )

		   One counter is the trigger counter that starts
                   the other counter this counter counts until
                   terminal count is reached.

		        parameter: { pulse freq, pulse witdh, xtal freq }

               4.) Interrupt Generator { single shot }

                   Clicks one interrupt every time the terminal 
                   count has been reached
                   
                   parameter: { click time, xtal freq }
                   result: -

               5.) Frequency divider

		   Timer is pulsed with external or internal oscillator
                   
                   parameter: { timebase, xtal freq }
                   result: -
                    

         o) D/A Converter
            ----------------
	    Global Configuration:
                chipset type,
		Reference Voltage, 
                resolution (12/16 bit)

	    Modes:

               1.) Single Shot Voltage output
                    
                   Programmable output ( simple )
      
                   parameter: { voltage }

               2.) Programmable Waveform generator
                     uses Interrupt Generator Atom

                   
               
          o) A/D Converter
             -------------------------
             Global Configuration:
		chipset type,
		Reference Voltage,
		resolution (12/16bit)

             Modes:

               1.) Single Shot Voltage Input

                  Software controlled A/D conversion
	          
                  parameter: -
		  result: {voltage}
		
               2.) Multichannel Analog-input

	           parameter: channel data
                   result: one voltage per channel

           o) Programmable Instrumentation Amplifier
              ---------------------------------------
             Global Configuration:
		chipset type


	     Modes:

               1.) Programmable Gain:

		   parameter: gain value
		   result:

           o) Programmable Multiplexer Circuit
              -------------------------------------

              Global Configuration:
                chipset type    

              Modes:

		1.) Single Channel Operation
                     
                    Enable channel

                    parameter: {channel no}


            o) PIO circuit
               ---------------------------------------

		Global Configuration:
                  chipset type

                Modes:

                 1:) Digital Input 
                 2.) Digital Output
                 3:) Single Line in/out