RE: [N8VEM: 419] Re: Non-working SBCs

["Andrew Lynch" <lyn...@yahoo.com>]

Hi Ken,

What parts do you and Littlebus have in common with your SBCs?  I am
specifically interested in the 16550 UART.

Please list out your parts or post a close up photo of your SBC so we can
compare your SBC and Littlebus's SBC.

It is possible that the XMODEM program is writing things to the UART control
register which are compatible with some 16550's but not others.  I am
starting to suspect this is the case if xm.com is the *ONLY* program that is
not doing what it is supposed to.  If there was hardware related freeze up
problem, I would think it happen with RAM monitor and/or CP/M usage as well.

In addition, XMODEM xm.com uses its own serial UART IO routines.  One way to
possibly debug this is to use the RAM monitor Intel Hex transfer routine and
send "instrumented" builds of xm.com over to see if you can find the
problem.  Alternatively, try to swap the 16550 with another brand to see if
the problem goes away.

The XMODEM 5.0 assembler source code is contained in the software zip file
found in the FILES section of the N8VEM Google Group.  It is fairly easy to
debug and it contains simple routines for adding "IAMHERE" style debugging
messages.  This is exactly how I got the xm.com program working on my
original TestPrototype since it had "issues" too.  It is possible the
changes I added back then may have had an effect on timing?

Would people who *HAVE* xm.com working please post what sort of brand of
UART 16550 they are using?  Please let's see if we can find some common
factors here to isolate this annoying bug.  I would love to see this one
squashed!

Thanks!  Have a nice day!

Andrew Lynch


> -----Original Message-----
> From: n8...@googlegroups.com [mailto:n8...@googlegroups.com] On Behalf Of
> Ken Harty
> Sent: Wednesday, August 06, 2008 3:44 PM
> To: n8...@googlegroups.com
> Subject: [N8VEM: 419] Re: Non-working SBCs
> 
> 
> Littlebus,
> 
> I think you're on to the same thing I've been experiencing the last
> several
> days. Seems to be waiting for something. Has XM.COM changed lately?
> I tend to think it may possibly be cable related as the modem 50 source
> code
> seems to play with the control lines and if I set TeraTerm to hardware
> control - nothing happens. Then again if XM is waiting for a NAK,,,,,,,
> same
> effect. Who should be sending the NAK?
> If there are any others out there using the XM.COM modem program, could we
> get a verified data cable schematic? Maybe a HEX file of a known working
> XM.com program?
> 
> 
> Ken
> 
> ----- Original Message -----
> From: "littlebus" <littl...@googlemail.com>
> To: "N8VEM" <n8...@googlegroups.com>
> Sent: Wednesday, August 06, 2008 2:12 PM
> Subject: [N8VEM: 418] Re: Non-working SBCs
> 
> 
> >
> >
> >
> > Hi Andrew,
> >                 Like Ken, I'm not having any success in getting xmodem
> > to complete a file receive (or file send). Hex downloads work well and
> > I've been able to run 'Scream'.
> >
> > After entering: xm r b:test.ttt , and with both the N8 xmodem dialog
> > and the teraterm dialog up and poised for action and nothing happening
> > I've 'scoped' the tx and rx pins on the n8 and there is no activity.
> > Shouldn't the N8 be sending NAK's every ten seconds?
> >
> >
> > >
> 
> 
>