[FADCA] USB to Com Port

[Chuck Hast]

On 9/8/06, bud Thompson <budt at cfl.rr.com> wrote:
>
> ----- Original Message -----
> From: "Chuck Hast" <wchast at gmail.com>
> To: "Florida Amateur Digital Communication Association"
> <fadca at mailman.qth.net>
> Sent: Thursday, September 07, 2006 10:03
> Subject: Re: [FADCA] USB to Com Port
>
>
> > On 9/7/06, Ray Cook <WD4SEN at bellsouth.net> wrote:
> >> I am getting ready to put up some FPAC switches here in Clay county, I
> >> have
> >> a computer with two USB ports and a card with 4 more USB ports.
> >>
> >> I need to find some adapters that go from USB to com port.
> >>
> >> I know there are several brands out there, and I have been told some do
> >> not
> >> work well..so I am relying on your experiences for choices of brands.
> >>
> >> IF you have a source for these adaptors I would appreciate that
> >> information
> >> too..
> >>
> >
> > I am running a cheap $9 one, it is considered non-standard because it does
> > not support the rs-232 control lines, but under kiss or 6pack those lines
> > do
> > not appear to be a issue since the system is sending packets to the TNC,
> > in the case of polled kiss or 6pack if the TNC can not accept a packet
> > because
> > it is full or busy, it rejects the packet until it is ready for it so
> > it has it's own
> > internal flow control. As far as I can see from the kiss protocol there is
> > no
> > control line support in the kiss code so even if they worked it does not
> > appear
> > that they would be used. There was the ability to use the CD line in kiss
> > to
> > signal to the kiss driver that the channel was busy but I was never able
> > to
> > get it to work in a satisfactory way. 6pack took care of all that as
> > it does it's
> > own handling with control packets between the 6pack device and the
> > computer.
> >
> > Hey, if the cheap one does not make you happy try the next one up... This
> > is ham radio, we gotta have fun, even with something as mundane as a
> > USB device!!! I have gone through several layers of exchanges before I got
> > what I was looking for, I used to feel guilty about doing exchanges but
> > some-
> > where along the way I lost it... I guess I learned from my wife who is
> > a fearless
> > exchanger/returner...
> >
> > --
> > Chuck Hast  -- KP4DJT --
> >=
>
> * * *
>
> If the USB/Serial adapter does not have control lines it might not be
> satisfactory for simply checking out the TNC with the stock AX.25 EPROM  to
> be sure it works - using Windows or Linux terminal programs.  Once the AX.25
> EPROM has been replaced with 6PAC or BPQKISS - it may be difficult to run
> the TNC through the paces just to check it out to be sure it works okay.
>
FPAC has a calibrate program that sends frames for TX setting, you can
also use listen to monitor RX in order to see if you are seeing good frames
coming in. You should not need control lines for just a simple tnc check, I
rarelly used them except on a few systems where I needed flow control in
order to keep things under check say feeding a terminal or some other
device that needed to be able to stop and start flow control. Under CRC/
polled KISS and 6pack the flow control is on a packet by packet basis.
Once you have the ax25 layer up and running on the linux machine you
can do all of your testing using the TNC in the fpac native cofiguration,
that is the configuration in which you should be testing the TNC.

> That brings me to another point:  If it doesn't exist now - we should have
> some standard terminal program in the Linux mix just for this purpose -to
> check out TNCs before putting them into service on FPAC.  Another thing that
> would be good for those TNCs using KISS mode with the AX.25 EPROM
> (Kantronics XKISS, PK-96 KISS 0$B) is to have an UP routine and a DOWN
> routine - where those TNCs are put into the proper mode automatically when
> FPAC starts and returned to terminal mode when FPAC shuts down.
>

Under Linux the most common (because it is in every distro) is minicom,
it is a 'telix like' (read almost a clone) of Telix. BUT if you have the TNC in
KISS or 6pack mode you should use the ax25 layer and test the bugger using
the 'call' routine. That allows you to connect to a distant TNC and
either keyboard
to it or send a file to it, and you will be exersizing the ax25 stack
in the Linux
box, something you want to do anyhow since fpac rides on top of ax25.

In the ax25 startup, there is a little script for each port that sends
the proper
kiss on string to tnc and also when ax25 is shut down there is one to pop it
out of kiss... 6pack is a special eprom and at this point we have not got a
eprom that will allow you to softswitch back and forth. One some of the PacComm
units there is a switch to switch between two banks in the eprom, with those
you can have regular tnc code in one bank and the specialized code in the
other, in this case polled/crc kiss or 6pack.

Here is what a tnc kiss setup looks like
#stty 19200 < /dev/ttyS0
#echo -e "\r\033 at K1\r" > /dev/ttyS0
#sleep 3

The first line sets ttyS0 to 19k2
The second line sends the KISS command to the TNC
The third one puts the process into sleep for 3 seconds to allow
the TNC to get changed over prior to hitting it with more data.


-- 
Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."