Serout

J^3

Good Morning Everyone,
·· I am trying to find out how long of a transmission line I can have using the SEROUT command.· In other words what is the longest distance I can have between a bs2p40 and a pololu micro servo controller.· Also while reading up on SEROUT I noticed the tpin can be driven or not.· Is this what you would use to increase the distance between devices.· One more, what exactly is a line driver.· Thanks a bunch in advance.

Mike Green

Like a lot of these things, it depends. You can generally count on transmitting at least several feet between two logic devices like a Stamp and servo controller. Reliability gets worse when you use higher Bauds (like 56K+ Baud) and gets better when you use lower Bauds (like 2400 Baud). As you get to longer distances (say 10 feet) and electrically noisier environments, things get less reliable. You can improve this be using higher voltages like the +12V/-12V of RS232 or the "balanced" signalling and the use of twisted pair wiring with RS422/RS485. Both of these require line drivers and line receivers which translate the voltages used in logic circuits (5V/0V or 3.3V/0V) to those used with these standards (RS232/RS422/RS485). The drivers and receivers also usually provide protection from static discharge and other voltage extremes that can destroy logic circuits.

J^3

Thanks Mike

As always you are a source of knowledge.· What about the driven or non driven I/O pin?· Whats that all about?

Mike Green

Driven or non-driven refers to open-collector/open-drain mode. The output circuitry of the Stamp connects the I/O pin to either ground or the supply voltage (+5V) in driven mode. In non-driven mode, the I/O pin is only connected to ground (or left unconnected). An external resistor "pulls up" the I/O pin to the supply voltage, but is too large to affect the voltage when the I/O pin is connected to ground. Do a Google search on "wiki open collector" for a more thorough explanation.

J^3

Thanks Mike,

I haven't tested anything, but I have a feeling I am going to need a line driver for my app.· I am going to be sending serial data from a bs2p40 to the servo controller over a distance of 60'.· I think it would probably be best for me to use the RS-232 set up but do not know how to select a driver.· Could you please help me with this issue.· Thank you.· Attached is the documentation for the servo controller, I believe I will not need a reciever because the controller accepts RS-232 signals.· Please correct me if I am wrong.· Thank you again.