John C. Ellingboe
john at guntersville.net
Wed Mar 1 20:30:22 CST 2006
Eric Dittman wrote:
> John C. Ellingboe wrote:
> > Tony Duell wrote:
> >>> On 3/1/2006 at 3:07 PM John C. Ellingboe wrote:
> >>>> Does anyone have information on the TI Travelmate LT220/V. A
> >>>> quick Google didn't turn up anything of value.
> >>>> I have acquired one with a pile of other items and have no idea
> >>>> how useful it might be. The power source, 18V DC did not come
> >>>> with it and there is no indication as to whether the center pin
> >>>> of the power connector is the positive connection or not.
> >>> Any external I/O connectors on it? Things like parallel port connections
> >>> will usually have their ground/return pins conected to the - side of the
> >>> power supply.
> >> While this is normally reliable, be warned it doesn't _always_ work. The
> >> HP48 calculator has the signal ground pin of the (minimal) serial port
> >> connected to the +ve supply line. There's an internal voltage converter
> >> which doubles the logic supply, the transmit data pin swings between
> >> this doubled supply voltage an logic ground, so about -5V to +5V wrt the
> >> logic +ve line which is the RS232 signal ground.
> >>> Last resort is popping the box open and checking the ground plane on the
> >>> PCB or any of the ICs (if the ground plane is buried) against the
> >>> connector.
> >> That's the one I do first. Why 'as a last resort'?
> >> -tony
> > I have raised the cover to look at the LCD and keyboard, checked
> > that the battery compartment doesn't have any battery contacts
> > in it and that it has three diffrent connectors for io and maybe
> > a buss extension. I haven't had time to open the case or
> > otherwise check anything out. As I said, a quick Google didn't
> > turn up anything as a starting point.
> I have an LT220 I can check tomorrow.
I would appreciate it Eric. It looks like it might be a useful
serial terminal if my guess is correct. It has a fairly small
footprint for space limited work areas. I'm sure the small LCD
has a very limited display also.
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