One TTL serin get info from two TTL serout pins Question
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I know I'm talking short circuits when I look for a way to make
one input get serial data from two serout-sources.
I could burn a few circuits to try it out, or ask this great group.
It's it possible to get data from two serout sources into a stamp,
if I mount a diode or resistor (or other device), to protect the
serout sources?
Stein.
one input get serial data from two serout-sources.
I could burn a few circuits to try it out, or ask this great group.
It's it possible to get data from two serout sources into a stamp,
if I mount a diode or resistor (or other device), to protect the
serout sources?
Stein.
Comments
>one input get serial data from two serout-sources.
>
>I could burn a few circuits to try it out, or ask this great group.
>
>It's it possible to get data from two serout sources into a stamp,
>if I mount a diode or resistor (or other device), to protect the
>serout sources?
>
>Stein.
2700
;--/\/\--;
| |
serout#1 ---o-->|----o---;
4148 |
|
2700 o
serin
;--/\/\--; |
| | |
serout#2 ---o-->|----o---o--/\/\-- com or V-
4148 2700
Active serout pulls high in diode wired OR configuration. Resistors
are pulldown to V-, or to common. In many cases you won't need the
Rs in parallel with the diodes.
The open baud modes of the Stamp are similar. They use an open drain
output to achieve the same effect, more than one serout/serin sharing
a line.
-- Tracy
oh, well, here goes.
1. That is what the 'open' baud modes are for.
You wire a pull-up resistor to the serial line,
then open the SEROUT drivers in open-baud mode,
so they "float up" via the pull-up resistor, and
"drive-down" via the pin driver. Since you then
never have the state where one drives high and
the other drives low, they can't burn each other
out. (a 220 ohm resistor in each driver line
will prevent damage in case of mistakes, though)
2. If you are talking 'true' RS-232 signals, then
the 'idle' state of a TX line is
at -12 volts. You will need to put a diode in
each TX line to insure current only goes out,
in parallel with a 10 Kohm resistor.
Note in either case, two senders 'talking' at the
same time will result in garbled data. With these
precautions, however, they won't result in equipment
damage.
--- In basicstamps@yahoogroups.com,