GPS - gps72, gps trackmaker and usb/serial converter problem

Author

gps72, gps trackmaker and usb/serial converter problem

Mike Scott

2005-10-13, 5:48 pm

I have a gps72 which has been working happily connected to the
motherboard's serial port of my desktop, and have been downloading
tracks and waypoints into gps trackmaker (gtm) using this.

I've just bought (off ebay) a cheap usb-serial converter, as the mobo's
serial port is inconvenient, being really meant for a serial link to
another machine, and I've an eye on use with a laptop in future anyway.
However, I find that gtm will not operate with this new serial port -
it sees the port (com3), but attempts to use it apparently receive no
data, and time out.

com3 appears to work in as much as I can use it for the link to the
other machine; there's no immediately obvious reason why it should fail
to talk to the gps72 as well.

Any ideas please?

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Dennis Pogson

2005-10-13, 5:48 pm

Mike Scott wrote:
> I have a gps72 which has been working happily connected to the
> motherboard's serial port of my desktop, and have been downloading
> tracks and waypoints into gps trackmaker (gtm) using this.
>
> I've just bought (off ebay) a cheap usb-serial converter, as the
> mobo's serial port is inconvenient, being really meant for a serial
> link to another machine, and I've an eye on use with a laptop in
> future anyway. However, I find that gtm will not operate with this
> new serial port - it sees the port (com3), but attempts to use it
> apparently receive no data, and time out.
>
> com3 appears to work in as much as I can use it for the link to the
> other machine; there's no immediately obvious reason why it should
> fail to talk to the gps72 as well.
>
> Any ideas please?

These USB-serial converters come with software. Have you installed it? Also,
a Win98 converter will not work with Win XP.

Mike Scott

2005-10-13, 5:48 pm

Dennis Pogson wrote:
> Mike Scott wrote:
>
>
>
> These USB-serial converters come with software. Have you installed it? Also,
> a Win98 converter will not work with Win XP.
>
>
Yes, I have installed correct XP drivers. In fact, the usb-serial
converter works nicely to provide a terminal emulator for a un*x box,
which is why I've been so puzzled as to why it fails with the gps72. The
converter appears to have been made by SemiTech, whoever they are.

I begin to think the issue is one of flow control - I've just been
looking at the garmin comms specs, and their protocol has its own
ACK/NAK controls. Playing about with a program called snooper running
on a un*x box to monitor what was happening shows that data is being
transferred, but becomes corrupt after maybe 4 or 5 packet exchanges,
and eventually the data transfer goes into a big pointlessly repetitive
loop. I have no idea what buffering is provided by the usb software -
but it's almost certainly going to be different from a physical uart.

Does anyone have any experience of these converters?

--
Please use the corrected version of the address below for replies.
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Mike Scott

2005-10-22, 5:48 am

Mike Scott wrote:[color=darkred
]
> Dennis Pogson wrote:
>

Just to close this off, I'll add that I've now tried a belkin usb-serial
converter (2nd hand off ebay), and this works fine.

--
Please use the corrected version of the address below for replies.
Replies to the header address will be junked, as will mail from
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