Re: [N8VEM: 474] Re: XM and transfer files

[Dr_Acula <mox...@internode.on.net>]

Goodness me - no wonder this is so confusing. We have the pinouts of
the N8VEM which seem to be random numbers on the 10 pin header, these
connect to the D9 and then the D9 connects to a D25 and on the D25 we
have pin some of the pins connected as a null modem but not all of
them. But I don't have a D25.

And to make things more confusing, normally a computer is a DTE and a
modem or a peripheral is a DCE. But the N8VEM is really a DTE itself,
so we have two DTEs connected to each other. Technically this would
normally use a crossover cable - ie on a D9 pins 2 and 3 would swap
over.

I think debugging this is going to involve going right back to first
principles. I'm going to need to study the source code and the uart
code. I need to know what DSR and DTR are actually doing on the N8VEM.
I can get around all the control lines from the PC end by bypassing
them in software and/or wiring them as a null modem.

First experiment - see if we can get this working with a 3 wire serial
connection and wire both ends as null modems.

Also, doing some detective work,  I think the header pinouts on the
N8VEM might be the correct pinout for an IDC connection - pin 9 is at
the end and this goes to ground to it really might be going to pin 5
on an IDC D9. And if so, then the middle pin would go to pin 3 on a
male D9 which would be correct for the N8VEM being a DTE and
outputting its data on pin 3.

Not sure why the 16C550 is using DTR and DSR rather than CTS and RTS.
I'll see if I can work that out from the code.