On 22/03/2011 10:13, Ruben J=F6nsson wrote:
>> I suspect an electrical difference between ports that I'm missing in the
>> datasheet as I have discovered by accident that a 1K resistor between
>> RB0 and the servo works, I'd still like to know what the difference is
>> so I know what/how for future reference and don't get caught again.
>>
> If it does work with the resistor and the servo input is a capacitive loa=
d or
> draws relatively much current it sounds like an RMW problem. Are any othe=
r bits
> in port B written or updated shortly after the servo output is?
>
> The resistor isolates the load from the pic pin and lets it swing to full=
 on or
> off much faster than without the resistor.
>

The fact it works with a resistor does make it look like a RMW problem=20
is possible, although I'm interested to know why PORTA works anyway.=20
Unless as Ruben says other PORTB bits are written to around the same=20
time regardless of which pin (RBx or RAx) is used. Could do with seeing=20
the relevant code for the servo pulses here.


--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.