Scope 1.0 for Linux ELF
                           =======================

      This is an oscilloscope program written in c using the XForms library.
   It uses the PC's parallel port for data input. The way it's done is as follows:
   first data bit 1 is set to 1 then to 0 to enable the a-to-d converter 
   ( ADC0801 ), then we read 4 bits of data from the multiplexer ( 74LS157 ) 
   placed after the a-to-d, then a 1 is sent to the second data bit and the other 
   four bits of data are read. The circuit is setup as follows:

   
       ---------------------------------------------------------<---- Data bit 1
       |
       |   ----------------                   --------------
       |   |            D0|-------->----------|      Select|----<---- Data bit 2 
       |---|Enable      D1|-------->----------|            |   
From       |            D2|-------->----------|          O0|---->---- Status bit 4 
Circuit->--|Ain         D3|-------->----------|          O1|---->---- Status bit 5
           |            D4|-------->----------|          O2|---->---- Status bit 6
From       |            D5|-------->----------|          O3|---->---- Status bit 7
555 timer->|CLK         D6|-------->----------|            |
           |            D7|-------->----------|            |
           ----------------                   --------------
               ADC0801                            74LS157

      The parallel port used as default is 0x378 but it can be changed within the 
   program. Other options such as number of points per screen update and a few more
   can also be set from the options dialog.

      The 555 timer is an easy chip to configure. Set it to between 70 and 100kHz.
   You will need the data-sheets for these 3 chips; these can be found at
   www.national.com in pdf format.

      One thing I haven't been able to figure out yet is the frequency response
   of this setup. If anyone can help me with that it would be greatly appreciated.
   Amplitude sensitivity is approximately 0.04 volts per bit change.

      Also, because this program accesses the hardware directly, you will need to
   run it as root ( pretty obvious ).

      If you have any questions regarding the circuit setup or operation just let me
   know through e-mail and I'll write back with the solution.

   Marcos Zini ( mzini01@fiu.edu )