cereal - EPOCH Serial Interface Emulator

Program cereal emulates the EPOCH V3 serial interface hardware:

                  Serial   H/W    Serial
    Writer ----->  I/F   <------>  I/F   -----> Reader(s)
                  Board    Link   Board

cereal provides a virtual software channel between a writer and one or more readers. The writer and readers are presented with the same network-based device interface that they use to communicate with the actual device drivers.

cereal creates a Channel object for each link it is emulating. Associated with each Channel object are:

• two listening ports (one to which writers connect and the other to which readers connect),
• a Writer object for the currently connected writer, and
• a list of Reader objects for the currently connected readers.

The Readers and Writers accept device configuration commands from their clients, but ignore everything but the baud rate. Other commands (e.g., device locks) are simply acknowledged.

When a write command is received from a Writer, the length of time required to output the specified amount of data at the current baud rate is used to compute the absolute time at which the data will be broadcast to the Readers and a write completion message will be returned to the Writer.

Invocation:

% cereal [-baud rate] [-daemon] [-debug] [-vperror]
         writerPort1 readerPort1 [... writerPortN readerPortN]

where

-baud rate

specifies the initial baud rate for subsequent links on the command line; the default rate is 2400 baud.

-daemon

causes cereal to become a daemon process.

-debug

enables debug output (written to stdout).

-vperror

turns vperror() message output on. vperror() messages are low-level error messages generated by libgpl functions; normally, they are disabled. If enabled, the messages are output to stderr.

writePort1 readerPort1 [... writerPortN readerPortN]

specifies the links to be emulated. Each link is specified as a network server port (i.e., service name or port number) to which writers connect and a second port to which readers connect.