Nightmare on Digitiser Street II: The full story

[David Houlder]

Hi all...

My previous message got abbreviated somewhere along the line. Here is (hopefully) the full text.

--------------------------- 

Right, this is driving me out of my mind...

I am trying to set up a Summasketch digitiser on a Sun IPX (SunOS 4.1.3)  to use with v.digit (grass 4.1, release 3). Shouldn't be too difficult, after all, I have the manual for the digitiser, and it says
	baud rate 	9600
	data bits	8
	parity bit 	odd
	stop bits 	1
Great! All the info I need. 

 So, I hop into the editor and set up digcap like this...

----
Summasketch:/dev/ttyb:ss3fmm_4:Summasketch III digitiser
----
... and there is no getty or lpd using ttyb.
Then I create ..../etc/digitizers/ss3fmm_4 like this...

----
# Summasketch III MM format
#
#       David Houlder, ANU, 1994
setup
{
    digname = Summasketch
    baud = 9600
    units_per_inch = 1000
    stop_bits = 1
    data_bits = 8
    parity = odd
}
... etc
----

Looks good so far. But when I plug the digitiser in and start up v.digit, nothing much happens: occasionally I get a few 'read error' messages, but certainly no sensible comms.

So then I write a few shell scripts to write/read from ttyb. Yes, the digitiser is happy: I send it commands, it responds properly (all done with 8 data bits, one stop bit, odd parity).

Right. time to play dirty. I trot out a vt220 terminal, set up the comms to match those of the digitiser, plug it in and start up v.digit.

Finally something happens. The first thing that v.digit seems to do with the digitiser is startquery, then loops on query until it gets a nice answer.


*But* the startquery command is gibberish (even when I put wait = 1 between each character). In fact, the only sensible config of the vt220 that seems to work is
	8 data bits
	*no* parity
	
Huh? So I play around with the 'parity =' and the 'baud =', but no luck.
And get this: I can even say...

	parity = bananas
	
...and it doesn't complain!!! Yet I am sure that my file is being used by v.digit because strings that I put in the startquery come out on the vt220.

What is going on here?
Is this a bug or what?
If so, who do I get in touch with?
...or how do I work around it.

Any help greatly appreciated




David Houlder			        Phone:	+61 6 249 4613
Geography Department	       	    (In Aust.:	(06) 249 4613)
The Australian National University	  Fax:	+61 6 249 3770