Sorry! I didn't think the ascii art would come out that bad!! It looked
a lot better when I sent it. I'll try describing the circuit in words.
Using 2 I/Os (RB0 and RB1 on a 16C505) I am trying
to drive two back to back LEDs and read a switch at the end of  2 long
wires . Each pin has a 470 ohm resistor in series with it and a .01 uF
cap shunted to ground after the resistor. At the end of the two long
wires there is a switch in series with a parallel combo. of  a  red and
a green led (pointed in opposite directions) and a 10K resistor. There
is also a 100k pullup at RB1. When I want to drive the back to back LEDs
( if the switch is closed) RB0 and RB1  are outputs . When I want to
read the switch RB0 outputs 0 and RB1 tries to read whether the switch
is closed ie. RB1 sees 1 if it is open , 0 if closed.
The wire I am driving(reading) is quite long approx. 300 ft. I am having

troubles reading the switch.I can read the switch ok if  I don't change
RB1  to an output . But thats no good because I have to be able to
switch the LEDs.I tried putting nops between my TRIS statements etc. A
code snippet is below  If anyone has any suggestions I'd be grateful

Check_Switch

 bcf PORTB,0 ; set input to switch 0
 nop
 nop
 nop
 nop
 nop
 nop
 nop
 nop
 movlw b'00000010'
 TRIS PORTB ; change RB1 to input
 nop
 nop
 nop
 nop
 nop
 nop
 nop
 nop
 bcf FLAG,POWER_ON
 btfss PORTB,1
 bsf FLAG,POWER_ON
 movlw b'00000000'
 TRIS PORTB ; put RB1 back to output
 nop
 nop
 nop
 nop
 nop
 nop
 nop
 nop
 return

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End of PICLIST Digest - 6 Feb 2000 to 7 Feb 2000 (#2000-39)
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