As I remember RTS and CTS as active low, but
regardless, I think you'd want to put in an appropriate pull-up resistor on
each line.
Scott Kellish
----- Original Message -----
From: Phil
To: p...@yahoogroups.com
Sent: Tuesday, January 27, 2004 12:00 PM
Subject: [piclist] Re: Waking Up UART from Sleep
how clean is RTS/CTS? I'd be a bit worried about
noise - it could keep the processor out of the sleep mode a lot if its an
issue.
--- In p...@yahoogroups.com, "Scott Kellish"
<skellish@c...> wrote: > Hi Bob, > If you have the luxery
of using RTS to wake you up, perhaps you can extend the concept and use
CTS to tell the PC its ok to send, that way you would'nt have to miss
any characters. PC asserts RTS, while your waking up, PC monitors CTS.
Once your fully awake, your assert CTS which causes the PC to start
sending. > > Scott Kellish > ----- Original
Message ----- > From: northwoodsfisherman > To: p...@yahoogroups.com > Sent:
Tuesday, January 27, 2004 8:06 AM > Subject: [piclist] Re:
Waking Up UART from Sleep> --- In p...@yahoogroups.com, "Charles
Linquist" <Charles@L...> > wrote: > > Good idea Charles. I think that will work for me. Thanks!
Still will > miss a few chars while it is coming out
of sleep (sorta like me while > drinking my morning
coffee) but I can deal with that. > > Thanks
Again > > Bob Ball >
WB8WGA> > > > Can you use hardware
handshaking? The RTS line could be used to >
wake up a > > PIC. > > > > Charles Linquist > > > > > > >
> -----Original Message----- > > From:
northwoodsfisherman [mailto:caravita@e...] > > Sent:
Monday, January 26, 2004 7:22 PM > > To:
p...@yahoogroups.com > > Subject: [piclist] Re: Waking Up
UART from Sleep > > > > --- In
p...@yahoogroups.com, "Phil" <phil1960us@y...> wrote: > > > > Thanks for the reply Phil. I
checked out the "downshifting" option > you > > mentioned but it requires to be running in either INTRC
or ER Mode. > The UART > >
application note warns about using these modes for a UART operation > due to > > clock variation might make
it unreliable with some RS 232 devices. > So guess > > should have a crystal. I could go to an external 32 to
200 khz > crystal (XT > > Mode) and
cut down the power consumption but can't get fast enough > baud rate > > (wanted at least 1200).
I think your external oscillator suggestion >
would > > work and is a possibility. I'll also try
tying RB1 to RB0 to wake > it up on > > a bit transistion external interrupt to see if that can
be made to > work when > > I
breadboard it. Am waiting for the MAX232 RS232 driver in the > mail. Thanks > > Again Bob
WB8WGA > > > > > > > > > yeah, sleep is
just a little too, well, deep. > > > > > > If its power saving you want, you could put the 628
into INTOSC > > mode > >
> at 37 khz. I'm not how the BRG needs to be set and you have to > figure > > > out how
handle the first byte that comes down . When you see > >
a > > > character, you then toggle up to 4 mhz.
I'm not sure if this > > meets > > > you app needs as INTOSC can be problematic for BRG
and I dont > > > immediately see a way to toggle
between INTOSC and XT or HS (so > you > > > can run at a frequency that can be used for
BRG). Look at the > > > "special
features" section of the data sheet. > > > > > > Maybe you could build a dual speed external
oscillator on CLKIN > and > >
> toggle it with a spare i/o pin (RA6 becomes free). See EC mode. > > > That's probably how I would do it
if I HAD to use a 16F628. > > > >
> > Several other PICs (look at the 16F88, for example) allow for > > > switching between external and internal OSCs.
You can have > primary > > > and
secondary oscillators and switch between them at will. >
> > > > > --- In p...@yahoogroups.com,
"northwoodsfisherman" > > <caravita@e...> > > > wrote: > > > > Hi > > > > Am experimenting with a PIC16F628 here and
would like put the > > > > processor in
Sleep Mode and then wake it up when a character is >
> > > received in the UART. Problem is that SLEEP seems to shut down > > the > > > > OSC
and thus the Baudrate Generator is not running to get the > > > > character. Read over the application note
(AN774) and data sheet > > > and > > > > I couldn't find any enlightening words
about how to handle this. > > > > > > > > I am wondering if it would be possible to also
hook the RX lead > > > from > > > > the RS232 line (RB1) to the external interrupt
pin (RB0). Before > > I > >
> > put the processor to sleep would enable interrupt RB0. After > > > exiting > > > > sleep
would start processing UART chars (might miss a couple) > and > > > > leave interrupt
masked until went back to sleep. > > > > > > > > Have I missed something in the data sheet? Has
anyone tried this > > or >
> > > have a better way??? > > > > > > > > Bob Ball > > > >
WB8WGA > > > > > > to unsubscribe, go to http://www.yahoogroups.com and
follow the > instructions > > > > > > ------------------------ >
> > >
-------------------------------- ---------- > Yahoo!
Groups Links > > a.. To
|