ttdriver: Thompson Stack Driver

Contents

• 1: Introduction
• 2: Invocation
• 3: C-Level Interface
  • 3.1: Initialization
  • 3.2: A/D Functions
  • 3.3: Digital I/O Functions
  • 3.4: GC Board Functions
  • 3.5: D/A Functions
  • 3.6: Counter Board Functions
• 4: Message-Level Interface

1: Introduction

2: Invocation

    ttdriver [options]
             -c <node> send msgs to memo on specified node
             -e <error filename>
             -h <msg header>
             -l add a level of debug messages
             -o <dev>[,<r>,<c>,<w>,<pass>,<warn>,<fail>,<debug>]
             -q Ask resident ttdriver to terminate
             -s no message sounds
             -v disable verbose to stderr
             -y disable system error message concatenation to messages

All the other options pertain to memo messages and are identical to the options on all other executables in this architecture.

Note that if ttdriver is run from sysinit.$NODE, it will be invoked before any memo program is resident, so it will not be able to log its messages with memo. In this case the appropriate invocation will likely be "ttdriver -v &".

3: C-Level Interface

3.1: Initialization

   unsigned short tt_init( void );

3.2: A/D Functions

   unsigned short tt_read_atod( unsigned short channel );

3.3: Digital I/O Functions

   unsigned short tt_write_digital( unsigned short dig_word,
             unsigned short value );
   unsigned short tt_read_digital( unsigned short dig_word );
   unsigned short tt_scdc_command( unsigned char cmd_no );
   unsigned short tt_scdc_multcmd( unsigned char *cmds );

3.4: GC Board Functions

   unsigned short tt_gc_reset( void );
   unsigned short tt_gc_byte( void );
   unsigned short tt_gc_read( gc_data_buf *gcbuf );
   unsigned long tt_gc_chan( unsigned short chan );

tt_gc_byte() is the lowest level routine, and reads a single byte of data from the GC board. Detailed knowledge of the GC counter board architecture is required in order to make use of this function.

tt_gc_read() returns all of the data currently available from the GC board for all channels in the gc_data_buf structure. The details of the contents of the structure are noted in the Message-Level Interface section. Since the GC board has an microprocessor of its own, it can buffer up to two seconds worth of data. That means you could call this function every second or two and still get all the data. On the other hand, you would have to write some non-trivial code to deal with these chunks of data when they arrive.

tt_gc_chan() is the simplest interface to the GC board. It returns the single latest value available from the GC board for the specified channel. In order not to lose data, this function must be called at the GC board's data rate (8 Hz).

3.5: D/A Functions

   unsigned short tt_dac_out( unsigned short channel, unsigned short value );
   unsigned short tt_dac_in( unsigned short channel );
   unsigned short tt_dac_enbl( unsigned short safe );

tt_dac_in( channel ) returns the last value written to the specified channel or 0xFFFF if the channel number is out of range.

tt_dac_enbl() determines whether the programmed values are enabled to the outputs of the D/A board.

3.6: Counter Board Functions

4: Message-Level Interface

ttdriver will also register the name huarp/exp/scdc in order to mimic the HUARP scdc program. Soldrv will use this name to locate ttdriver in order to cycle digital commands efficiently.

ttdriver will recognize two types of messages: the new board-specific messages and the scdc messages.

The board-specific messages use the following structure. The first two bytes of the message are a signature to uniquely identify the message. The SCDC interface was defined before this sort of convention was established, so the SCDC message structure is different. Fortunately, we have not run into any sort of conflict to date.

Each special function has a different function code enumerated in the ttmsgtype. Most functions require an address, and many require data. If a function does not require one or the other, it need not be sent.

          typedef struct {
            unsigned short signature;   /* 'tt' */
            unsigned short function; /* ttmsgtype */
            unsigned short address;
            unsigned short data;
          } Send_to_tt;

          typedef enum {
            TTMSG_READ_ATOD,
            TTMSG_WRITE_DIGITAL,
            TTMSG_READ_DIGITAL,
            TTMSG_GC_RESET,
            TTMSG_GC_BYTE,
            TTMSG_GC_READ,
            TTMSG_GC_CHAN,
            TTMSG_DAC_OUT,
            TTMSG_DAC_IN,
            TTMSG_DAC_ENBL,
            TTMSG_QUIT,
            TTMSG_MAX
          } ttmsgtype;

          typedef struct {
            unsigned short signature; /* 'tt' */
            union {
              unsigned short shrt;
              unsigned long lng;
            } value;
          } Reply_from_tt;

In case of error, gcbuf.end_offset[0] will be set to 0xFFFF.

          typedef struct {
            unsigned short end_offset[ N_GC_CHANNELS ];
            unsigned long samples[ MAX_GC_SAMPLES * N_GC_CHANNELS ];
          } gc_data_buf;

          typedef struct {
            unsigned short signature; /* 'tt' */
            gc_data_buf gcbuf;
          } Reply_from_gc;

          typedef struct {
            unsigned char signature[2]; /* DASCMD, DCT_SCDC (1, 3) */
            unsigned char command;
          } Send_to_scdc;

          typedef struct {
            unsigned char signature; /* SC_MULTCMD (11) */
            unsigned char commands[ MAX_MSG_SIZE ];
          } Mult_send_to_scdc;

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