a baudrate question about Parallax Servo Controller

hsiaochung

Colud anyone explain
what is the difference between the two case

baud con 396 'for bs2
Sdat con 15

serout Sdat,baud,[noparse][[/noparse]"!SC",r,c,position.LOWBYTE,position.HIGHBYTE,CR]
serout Sdat,baud+$8000 ,[noparse][[/noparse]"!SC",r,c,position.LOWBYTE,position.HIGHBYTE,CR]


In the pbasic manual

· select driven or open output
····
··· driven = 0
··· open· = $8000

·what is the difference between driven and open

Mike Green

Driven means that the Stamp switches the I/O pin between 0V (ground) and +5V (Vdd) to produce the serial signal.

Open means here that the Stamp switches the I/O pin between 0V (ground) and a high impedance state. This is used when several devices are connected in parallel and there's always a pullup resistor somewhere connected to +5V (Vdd) to "pull up" the signal to +5V when none of the devices are actively pulling the signal line low (to 0V).

You can't connect devices in parallel when they're "driven". If, for some reason, one device has switched the signal to ground and another has switched the signal to Vdd, you'll have a short circuit between Vdd and ground which can damage one or more of the devices.

hsiaochung

Thanks for Mike
I appreciate your help