Chris said:
MAX232 -
MAX232
too!
yep thats the article i followd, the pic a/d does pickup noise when
plugged into the serial port, verified by readings and a scope, all
ic's
have filtering caps ad is also filtered, if i unplug the serial gnd
from
the pic board the readings are clean as soon as i plug it back in i
see
a wave......
How many milli-volts are we talking about? I wonder if you have a
ground-loop problem? Check your earthing.
unless is there a way to split off my pic power supply for that
circuit
instead of the serail bu that would not cause noise??
Could you post a schematic and/or photo of your layout?
You might be able to do this without the MAX232: drive the opto LED,
via a series current-limiting resistor, directly from the PC serial
port. Going the other way, if you can independently control DTR and
RTS, you could do this:
DTR (+12V)------[1K]------[opto-transistor]-----RTS (-12V)
Connect RxD to the junction of the 1k resistor and the transistor.