[ECOS] Re: Ignoring packet error...

[ECOS] Re: Ignoring packet error...

[richard.panton]

  When I first connected the Assabet board to my PC using the Intel
serial/parallel cable, I got these errors. I could see output from the
RedBoot monitor, but nothing I typed had any effect, and running GDB gave
the 'Ignoring packet error' messages.

  It turned out that the serial cable is a three wire cable - ie. does not
provide handshaking signals - and that for some reason, Linux ALWAYS uses
some form of handshaking (I think DSR/DTR handshaking).

  So, I wired up the connector at the PC end to connect RTS & CTS, DSR &
DTR, and to permanently enable DCD. Now it works fine...

Richard Panton
3G Lab Ltd.

Re: [ECOS] Re: Ignoring packet error...

[Jonathan Larmour]

"richard.panton" wrote:
> 
>   When I first connected the Assabet board to my PC using the Intel
> serial/parallel cable, I got these errors. I could see output from the
> RedBoot monitor, but nothing I typed had any effect, and running GDB gave
> the 'Ignoring packet error' messages.
> 
>   It turned out that the serial cable is a three wire cable - ie. does not
> provide handshaking signals - and that for some reason, Linux ALWAYS uses
> some form of handshaking (I think DSR/DTR handshaking).
[ sorry for reviving this old topic ]

Did you check using a terminal emulator like minicom that there definitely
was no handshaking? I know the default is to do handshaking but it can be
set off. minicom is useful because it makes the current setting obvious.

stty would probably do as well of course if you are sufficiently versed in
that.

Jifl
-- 
Red Hat, 35 Cambridge Place, Cambridge, UK. CB2 1NS  Tel: +44 (1223) 728762
"Plan to be spontaneous tomorrow."  ||  These opinions are all my own fault

Re: [ECOS] Re: Ignoring packet error...

[richard.panton]

On Tue, 7 Nov 2000, Jonathan Larmour wrote:

> "richard.panton" wrote:
> > 
> >   When I first connected the Assabet board to my PC using the Intel
> > serial/parallel cable, I got these errors. I could see output from the
> > RedBoot monitor, but nothing I typed had any effect, and running GDB gave
> > the 'Ignoring packet error' messages.
> > 
> >   It turned out that the serial cable is a three wire cable - ie. does not
> > provide handshaking signals - and that for some reason, Linux ALWAYS uses
> > some form of handshaking (I think DSR/DTR handshaking).
> [ sorry for reviving this old topic ]
> 
> Did you check using a terminal emulator like minicom that there definitely
> was no handshaking? I know the default is to do handshaking but it can be
> set off. minicom is useful because it makes the current setting obvious.
> 
> stty would probably do as well of course if you are sufficiently versed in
> that.

I've just done some more experiments.

The Assabet serial cable has pins 2, 3, and 5 connected (ie, RxD, TxD, and
GND). I've added connectors between 1 and 4 and 8 (ie. DCD, DTR, and CTS,
all connected together - NOTE all references to pins and connectors are at
the Linux end of the cable).

With this cable, under Linux, I ran gdb. Everything worked. I removed the
additional connectors (without exiting gdb). Everything still worked!!!

I rebooted to WindowsNT (without power-down), and ran HyperTerminal. The
RedBoot prompt appeared, and I could type commands.

I rebooted to Linux (again without power-down). Running "cu -s 38400
--nostop -l ttyS0" and reseting the Assabet board produced the RedBoot
startup banner, but pressing Enter (or any other key) had no result.
Similarly, gdb could not connect to the board (and "stty -a < /dev/ttyS0"
hangs without producing output).

I powered down the PC, and then booted Linux. Still no response from cu or
gdb. (or stty, although interestingly, whether "stty -a" works seems to
depend upon what was run last/is running).

I connected pins 4 and 8 (DTR - CTS!!), and cu began working (i.e.,
pressing Enter gave a new RedBoot prompt). stty produced results. However,
gdb could still not connect.

I connected DCD - DTR - RTS. cu and gdb now work.

Connecting all these pins together may not be an optimal solution, but it
does work (FOR MY SERIAL HARDWARE, DRIVING A THREE WIRE LINK). And no, I
don't have a proper explanation for WHY it doesn't work without these
connectors. However, I came across pretty much the same symptoms in the
mid-90's when writing a terminal emulator for EPOC devices
( http://www.iota.demon.co.uk/psion/hermes/hermes.html ), and attempting to
log in to my Linux box; I had to modify a cable (tying DCD active at the
Linux end) to get past the login prompt. [Since then, new getty versions
have come along that allow me to log on with my terminal emulator without
cable hacks].