Rander box

[Eric Hughes <hughes@soda.berkeley.edu>]

>   It will have two serial connectors,   one an input,  and other the
>output,   and connect to a modem or serial port.   Physically,  it should
>have dip switch to select baud rate,   and an on-off switch.

Some simplifications I might suggest:

I only think you need an output connector.  See below.

If you can power it off the RS-232 line, you won't need a power
switch.  You should be able to draw enough power off, say, the DTR
line to power a simple thing like this.

For a dedicated random number generator with low bandwidth, there's
not much reason for variable baud rate.  I'd use a fixed baud rate of,
say 1200, or even 300.  If you make it low enough you could just
kludge together a serial interface, but with the low cost of UART's,
it's probably not worth it.  You might also consider using a PIC, which
has built-in serial.

>   When switched on,   and a "cr" (or some other character) is sent to it,
>random bytes will stream out continiously.   

I'd just make the thing spew continuously.  It's not like you're
losing real, er, information if you ignore a few random bits.  This
way you don't need the added circuitry for switching on and off.

The actual use of this thing is going to require a device driver to
buffer up random bits for later use.  So all the flow control to the
higher layer happens there anyway.  And if the UART buffer overflows,
so what?

Eric