On Sun, Sep 19, 1999 at 04:54:51PM +0100, Dan Rosenfeld wrote:
> Hi all,
>
> >From looking at the archive, I can see that this is a somewhat FAQ.
> Unfortunately, I'm having trouble assembling all that I've read into a
> coherent picture applicable to my simple problem....
>
> I'd like be able to send characters (debugging printfs) from the 16LF84 in
> my circuit to my PC serial port W/O USING A LEVEL CONVERTER CHIP. I only

I'd rather suggest using a small voltage shifter (see the attached
schematics, sorry for binary attachment; I've compressed it to spare
bandwidth).
T1,T2 & T4 may be almost any npn low power transistors (eg. BC107).
T3 almost any pnp low power transistor with UCEmax >=30V (eg. BC177).
Using of switching transistors is however recommended.
Diodes - almost any low power impulse diodes.

> need this to work on my PC for debugging purposes (it's not a production
> circuit) and at low baud rates and short cable distances. I'm also wondering
> whether I can get away with running this all at Vdd = 3.0V (thus the LF84)
> or will I need run at some higher voltage while debugging.

Take the higher voltages from the RS232 port (see my circuits).
>
> I'm pretty clear on the PC side (terminal emulator app or basic program),
> but I'm not certain of the exact electrical connections on the pic side.
> I've seen mention of using anywhere from 1k to 1meg in series w/o tx/rx
> lines and along with some mention of pulldowns on these lines.
>
> Also, do I need to do anything special with any of the other rs-232 lines
> such as RTS/DTS, etc. or can I just let them float? (Assuming the pc
> software is configured correctly.)
If you switch off the hardware handshake in the PC software, don't care of
the input lines (leave them floating).
--
                                Hope this helps
                              Wojciech M. Zabolotny
        http://www.ise.pw.edu.pl/~wzab  <--> wzab@ise.pw.edu.pl

http://www.debian.org  Use Linux - an OS without "trojan horses" inside

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