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Ralph Hempel wrote in message <000001beb0e4$f9d0df00$0500000a@pro150>...
> I'll back you up on this. My pbFORTH sends a simple character stream and it
> seems to work fine. No complements are necessary.
I'll back you up on this as well. I did some experiments using two
towers connected to two different PCs, and found that I could send raw bytes
from one PC to the other without any complements.
Also remember that the RS-232 start and stop bits will inject both logic
levels every 10 bits or so, which should prevent long series of 0's or 1's
from causing ambient light level problems, although I must admit that I am
not completely familiar with the issues involved in IR transmission and the
Lego tower hardware.
> I sure would like to be
> able to keep the RCX tower alive, though. I wonder if it's the character • going
> through that keeps the tower alive, or if wiggling RTS or other control • line up
> and down would be enough.....
Further tesing showed that toggling the various RS-232 control lines via
software had no effect on keeping the tower alive. As far as I can tell,
the tower only wakes up when it sees a start bit on the data line. (I
didn't have a breakout box to test this theory, but I plan to hack together
a serial cable with just two wires - transmit and ground - to verify that
the tower only needs a signal on this one wire to wake up.)
I'll post the results when they are in, but it looks like the only way to
keep the tower alive is to periodically transmit at least one byte from the
PC. Since most network protocols require periodic acknowledge or heartbeat
messages, this should not be an insurmountable problem, but it definitely
limits how long the RCX can talk without pausing to let the PC respond.
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