Rosetta progress report WAS: translator question

[nobody@xxxxxxxxxxxx (Dave Houston)]

I have a circuit board layout that I think will work. I'll stare at it for a
few more days. I usually find that causes traces and solder pads to move
around mysteriously ending up in locations where I don't recall placing
them. I'll send it off this weekend and should have it about 2-3 weeks after
that. In the meantime I can start on the code using a BX24-AHT board

Mouser does not stock any through hole RTC chips so I will use SMT and will
forget about using any of the supported serial devices for the RTC backup.
This will save a bit of code since there will only be the one chip to
interface with. I'll leave the choice of supercapacitor to the user. Mouser
stocks 3 that will fit the space I've alloted. They will provide anywhere
from 2-3 days to more than a month backup for the RTC chip.

I've settled on I²C for the RTC chip and will use the ZX-24's hardware I²C
implementation which can run at 410kHz. The I²C bus can support another
EEPROM chip should it prove necessary to increase the space for user data.

To use Rosetta with any of the controllers that normally use a TW523 (or
PL513), the newly liberated TW523 (or PL513) will need to be attached to the
other TTL port in order to supply a ZC signal for Rosetta and the controller
(e.g. HAI, JDS, Ocelot). The controller, Rosetta and TW523 (or PL513) will
share the ZC signal. I think the ZX-24 will be fast enough to have the
controller receive pin follow the ZX-24 receive pin which will be listening
to the TW523. This way, there will be no delay in the controller receiving
what's on the powerline (or at least what the TW523 is willing to divulge on
that topic). When the controller transmits, there will be a delay as Rosetta
will need to see a complete code before deciding if it needs translation or
merely needs to be sent to the powerline via the TW523 (or PL513). This
should allow for sending/receiving a mixture of X-10, UPB and 2414S
powerline commands

Rosetta will also be able to program delays (~2ms minimum, infinite maximum
resolution) as needed between signals it sends to the powerline.