I am trying to get data (GPS position) from an LX7007 into Tophat via a
serial cable connected to the LX7007's "PDA" port.

I've added a max232 type voltage converter chip to the internal serial
(not USB) port of both a Nook e-reader and a Kobo Mini e-reader. Each
of them get GPS and FLARM data if I connect them to a FLARM via that
interface.

Connected to the LX7007, the Nook works fine at 19200 baud as promised.
Tophat (using its LXNAV driver) says it is getting GPS, baro, airspeed
and vario data.

But I can't seem to get it working with the Kobo. When I click
"monitor" (in Tophat) on the incoming data port, if the baud rate I set
is too high or too low I often see a series of periods, which means it
sees ones and zeros coming in but they don't make sense. If I set it to
the correct speed of 19200 then it shows NOTHING.

This is with the same cable from the LX that works with the Nook, and
with the same input port on the Kobo that works with the FLARM, and the
same cable from the FLARM also works with the Nook.

Puzzled.

On 3/7/2022 8:48 AM, Moshe Braner wrote:
> I am trying to get data (GPS position) from an LX7007 into Tophat via a
> serial cable connected to the LX7007's "PDA" port.
>
> I've added a max232 type voltage converter chip to the internal serial
> (not USB) port of both a Nook e-reader and a Kobo Mini e-reader.  Each
> of them get GPS and FLARM data if I connect them to a FLARM via that
> interface.
>
> Connected to the LX7007, the Nook works fine at 19200 baud as promised.
> Tophat (using its LXNAV driver) says it is getting GPS, baro, airspeed
> and vario data.
>
> But I can't seem to get it working with the Kobo.  When I click
> "monitor" (in Tophat) on the incoming data port, if the baud rate I set
> is too high or too low I often see a series of periods, which means it
> sees ones and zeros coming in but they don't make sense.  If I set it to
> the correct speed of 19200 then it shows NOTHING.
>
> This is with the same cable from the LX that works with the Nook, and
> with the same input port on the Kobo that works with the FLARM, and the
> same cable from the FLARM also works with the Nook.
>
> Puzzled.

Never mind the Nook and Kobo and LX7007 specifics. I am fishing for
some conjecture as to how this behavior is even possible with RS232
serial connections:

LX -> Nook ok
FLARM -> Nook ok
FLARM -> Kobo ok
LX -> Kobo not ok

- and that is with the same (separate) FLARM and LX custom cables.

They both work OK with the FLARM output. So I know the TTL-RS232
conversion is working, and that that cable has the in and out
pins right. The Nook works with the LX7007, so I know that cable has
the in and out pins right. But the LX does not work with the Kobo.
Still stumped.

Some unlikely ideas: Maybe the LX7007 sends voltages that are marginally
within the RS232 standard, and one max232 chip module manages with it,
and the other (of same model) does not? Perhaps the LX7007 serial
output on the "PDA" port is TTL level not RS232? The manual doesn't
say, but it does say "RS232" for the other ports. The PDA port also
sends 5V power which seems incongruent with RS232 levels, but maybe that
made sense back when Pocket PCs were the thing.

Or maybe the LX7007 sends bytes with bits different from the typical
8-N-1, and the UART in the Nook accepts it and the UART in the Kobo does
not?

How do you supply pwr/gnd to each of the devices?

On 3/9/2022 3:35 PM, Darren Braun wrote:
> How do you supply pwr/gnd to each of the devices?
>

Both the Nook and the Kobo can run on their internal batteries for a
while. But not long enough for a long flight. They both have USB power
input. I run both the e-reader and the FLARM or LX off a 12V battery.
The FLARM cable assembly I built includes a 12V to 5V converter. The LX
cable assembly I built takes the 5V power available in the LX "PDA"
connector along with the serial data.

The ground wire is NOT common to the data and power supply, since they
attach to the e-reader via separate cables. But data and power do
eventually connect to the same ground on both ends, I suppose.