Re: Serial Communications

["anoneds@netscape.net" <anoneds@netscape.net>]

tolsen64 wrote:
> Does the GS just dump characters if the incoming text is too fast?  Or
> can that even happen?
>
> Here's what I have:
>
> GS -> Ethernet Modem -> Internet.
>
> When I telnet out to a server (NNTP or SMTP), I lose half the
> characters in the response, so what i'm getting back is useless.
>
> Both the GS and the Ethernet Modem's serial speed is set to 19200.
>
> I thought it might be handshaking so I spent the day studying every "GS
> Handshaking" article I could fine (there are a lot of different
> versions of the beast).  All of them go from the MINI DIN-8 to DB-25.
> My Ethernet Modem has a DB-9 connector so I tried to "adapt" by
> cross-referencing the DB-25 signal names to the same on the DB-9.  But
> I couldn't get it to work (I couldn't transfer data at all) whichever
> cable i built.
>
> The cable I have working now works great as long as i'm not receiving
> more than a few characters at a shot.  The BBS currently runs using
> this cable.  I got this cable working by trial and error and I'd have
> to ohm it out to tell you what it's pin-to-pin connections actually
> are.  But it evidently doesn't handshake.
>
> The other cable I have is one that I used when I had the GS hooked up
> through the PC to the internet.  It always worked fine.  I got
> everything that was coming in (I had internet email working on my bbs).
>  But that cable doesn't work with the Ethernet Modem.
>
> I'm wondering if the Ethernet Modem is just too-darn-fast for the GS.
> I've tried turning on the Buffering & FIFO options in the Ethernet
> Modem to no avail.  If I turn on the DTR Handshaking in the Ethernet
> Modem, I get no communications at all.  It only works if I set it to No
> Handshaking or Xon/Xoff.  But I still have the problem of losing data
> when a bunch comes in.
>
> It seems as if I have hit a brick wall here...

You need some sort of CTS-RTS handshaking here. CTS tells the other end
it is "Clear to Send" some data. RTS tells the other end that it is
"Requesting to Send" some data.

My old TI didn't even have RTS hooked up, so we TIers cooked up using
another signal for that. Of course it isn't automatic like RTS is
supposed to be, but we can turn it off/on when needed, and get 19,200
without a problem. Even done 38,400 without much difficulty. Just can't
get 56k both ways.

I used a Lantronix UDS-10 (serial-ethernet) on my TI at 38,400, with
RTS-CTS with no data loss... until I fried my Lan card (probably moved
it with power cord still plugged in...)