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> 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,