PDPRP Technical LBC Description

The C Code

• Initialize variables and arrays

• Initialize digital I/O ports - this is the initialize_io() routine which sets up access to the Computer Boards Digital I/O board we use to communicate with the LBC and to the Cyclades board serial ports we use to talk to the host computers and eventually, VCRs. It is expected we will also use the digital I/O ports to control the filters and filter wheels as well.

  There are a few things to note in this routine. First, is the ioperm() which must be run as root in order to execute properly. This is why I have created the script in /home/ingrid/obs/bin/rootfix which sets the permissions on lbc so the ioperm() call will be successful. The rootfix script needs to be run as route to work. It contains the following lines:

  #
  cd ~obs/pdprp
  chown root lbc
  chmod 4711 lbc
  

  Second, the Base Address for the Digital I/O board is 0x300UL. However, since we apparently blew some 82C55A chips on the I/O card, I have changed the code to make the Base 0x310UL and have re-cabled the board accordingly. We are therefore currently using different ports than we had originally. The I/O board is broken up into 8 groups of 3 ports each with 8 bits per port, for a total of 192 lines. Once we replace the defective chips and put the wiring the way it is supposed to be, we should change the definition of the BASE keyword in lbc.c. BASE is a #define'd variable defined at the top of the code.

  Third, the serial ports in this routine are allocated from /dev/ttyC0 to /dev/ttyCX where X is given by the code's NUMSPORT variable. Therefore, if additional ports on the card are being assigned tasks that should not be set-up by this routine, they should be the ports starting at /dev/ttyC7 and working down, so that the ports from /dev/ttyC0 and up are all allocated in the loop in initialize_io.

  The file Hardware.notes contains information on the current pin and port assignments. The documentation we received with these two hardware boards are in the computer Ingrid's documentation box.

• Read in Initial Parameters - this is the call to read_bdata(). lbc.tcl, every time a new cycle is started, or the program exited, saves the current bench settings in the file bench.params. When a cycle is started, the Tcl/Tk creates the parameter file, and the C code reads it. So, under normal circumstances, the C code does not have to read the parameter file initially, but it does. If the user Quits the program, without starting any cycle, the Stopping/Quitting routines need the parameters. (They, in reality don't, but that's the way they're coded.) So, the parameters are read in now, just in case the user quits without starting any cycle and loading in the data that way.

• Set up the Tcl/Tk GUI - this is done in the tcl_initialize() call. It defines the Tcl/Tk program file, (lbc.tcl) as well as creates the C commands it will call:
  • Cstart - the start_cycling() C routine which starts the cycle going.

  • Cstop - the stop_cycling() C routine which stops the cycle.

  • Cignore - the error_ignore() C routine which sets up the C array of errors to Ignore when they occur. (See the LBC Errors page.)

  • Cdenotify - the error_denotify() C routine which tells the C code the user has acknowledged an error condition in the GUI.

• Start the Main Event Loop - this is the loop that is run continuously to accomplish the main functions of the program. The loop does a few different things:
  • Check Serial Ports for incoming commands (the check_serial() call).

  • Check the Cycling requirements and go to the next bench if everyone is ready.

  • Update the GUI - via the Tcl_GlobalEval(Interp,"update\n") command.

  • Sleep - sleep for 0.1 s in an attempt to keep this loop from running like a bat out of hell doing mostly nothing but eating up Ingrid's CPU.

The Tcl/Tk Code