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kayakkhan
Guest
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 Posted:
Wed Nov 23, 2005 3:54 pm Post subject:
Garmin GPS 75 |
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I have recently purchased a Garmin GPS 75 with power/data cable and cradle.
A google search has not provided any useful info on connecting this unit to
a pc for use with wingps or the like via rs232. I imagine this is because
the unit is quite old. Does anyone out there have a wiring diagram?..or
perhaps a link to a website?
Thanks in advance. |
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David Lee
Guest
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| Posted:
Wed Nov 23, 2005 5:08 pm Post subject:
Re: Garmin GPS 75 |
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kayakkhan wrote ...
| Quote: | I have recently purchased a Garmin GPS 75 with power/data cable and cradle.
A google search has not provided any useful info on connecting this unit to
a pc for use with wingps or the like via rs232. I imagine this is because
the unit is quite old. Does anyone out there have a wiring diagram?..or
perhaps a link to a website?
Thanks in advance.
|
That's funny because my Google search ("GPS75 Manual") immediately returned:
Pin 1: 12 volts
Pin 2: 0 volts
Pin 4: Data Output
Pin 5: Data Input
which I assume is what you are looking for.
If you had bothered to look properly you would also have found the full
manual for the GPS75 on the Garmin website at (not suprisingly!)
http://www.garmin.com/manuals/GPS75_OwnersManual.pdf
The manual makes no mention of RS232 but a simple search on "NMEA RS323"
reveals that there are slight differences in voltage level specificaton that
one site claims can possible lead to unreliable comms or serial port damage
with some older equipment. I don't know whether the risk is significant
(I'm sure someone else can comment) but the same site offers you an
NMEA/RS232 interface cable for less than 10 UK pounds including tax.
It doesn't require much greater intelligence than that of the average
termite to find all this information on-line within a couple of minutes so
please try a little bit harder next time!
David |
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kayakkhan
Guest
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| Posted:
Wed Nov 23, 2005 5:08 pm Post subject:
Re: Garmin GPS 75 |
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"David Lee" <davidlee_malvern@dont.use.this.bit.hotmail.com> wrote in
message news:_pudnV3SPaEk-RneRVnyvg@eclipse.net.uk...
| Quote: | kayakkhan wrote ...
I have recently purchased a Garmin GPS 75 with power/data cable and
cradle. A google search has not provided any useful info on connecting
this unit to a pc for use with wingps or the like via rs232. I imagine
this is because the unit is quite old. Does anyone out there have a wiring
diagram?..or perhaps a link to a website?
Thanks in advance.
That's funny because my Google search ("GPS75 Manual") immediately
returned:
Pin 1: 12 volts
Pin 2: 0 volts
Pin 4: Data Output
Pin 5: Data Input
which I assume is what you are looking for.
If you had bothered to look properly you would also have found the full
manual for the GPS75 on the Garmin website at (not suprisingly!)
http://www.garmin.com/manuals/GPS75_OwnersManual.pdf
The manual makes no mention of RS232 but a simple search on "NMEA RS323"
reveals that there are slight differences in voltage level specificaton
that one site claims can possible lead to unreliable comms or serial port
damage with some older equipment. I don't know whether the risk is
significant (I'm sure someone else can comment) but the same site offers
you an NMEA/RS232 interface cable for less than 10 UK pounds including
tax.
It doesn't require much greater intelligence than that of the average
termite to find all this information on-line within a couple of minutes so
please try a little bit harder next time!
David
|
The termites thank you.
As you quite rightly observe, the manual doesn't mention connection to PC
via RS232, which was my question as more than a brief perusal of my query
would have determined. I appreciate the time taken to reply however. |
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David Lee
Guest
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| Posted:
Wed Nov 23, 2005 5:08 pm Post subject:
Re: Garmin GPS 75 |
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kayakkhan wrote ...
| Quote: | The termites thank you.
As you quite rightly observe, the manual doesn't mention connection to PC
via RS232, which was my question as more than a brief perusal of my query
would have determined. I appreciate the time taken to reply however.
|
Looking at the PC end of the system - Pin-out for a normal 9-pin D-type PC
connector is:
Pin 2: Data Out (RX Data)
Pin 3: Data In (TX Data)
Pin 5: Ground (0V)
(where Data In/Out is relative to the GPS and RX/TX is relative to the PC)
For a DB-25 serial connector:
Pin 2: Data Out (RX Data)
Pin 3: Data In (TX Data)
Pin 7: Ground (0V)
As far as I can see the votage level specifications are:-
RS232:
Mark (1): -5 to -15 volt
Space(0): +5 to +15 volt
NMEA 0183:
Mark (1): <0.5 volt
Space (0): >4.0 volt
Another obvious simple [hymenoptera level again :-) ] Google search for
"garmin gps-75 rs232" would point you at a document you could be looking for
on the Garmin website: "GARMIN GPS Interface Specification"
http://www.garmin.com/support/pdf/iop_spec.pdf
General comments (NOT receiver specific) include:
"The default Physical protocol is based on RS-232. The voltage
characteristics are compatible with most Host devices; however, the GPS
transmits positive voltages only, whereas the RS-232 standard requires both
positive and negative voltages. Also, the voltage swing between mark and
space may not be large enough to meet the strict requirements of the RS-232
standard. Still, the GPS voltage characteristics are compatible with most
Host devices as long as the interface cable is wired correctly." In other
words voltage levels are consistent with the NMEA 0183 standard but the GPS
is designed to safely accept RS232 signals so nothing should be damaged in
either direction.
It's going to be up to you whether you decide to risk it!
David |
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kayakkhan
Guest
|
| Posted:
Wed Nov 23, 2005 5:08 pm Post subject:
Re: Garmin GPS 75 |
|
|
"David Lee" <davidlee_malvern@dont.use.this.bit.hotmail.com> wrote in
message news:QOidnf_K_JcCCRneRVnytQ@eclipse.net.uk...
| Quote: | kayakkhan wrote ...
The termites thank you.
As you quite rightly observe, the manual doesn't mention connection to PC
via RS232, which was my question as more than a brief perusal of my query
would have determined. I appreciate the time taken to reply however.
Looking at the PC end of the system - Pin-out for a normal 9-pin D-type PC
connector is:
Pin 2: Data Out (RX Data)
Pin 3: Data In (TX Data)
Pin 5: Ground (0V)
(where Data In/Out is relative to the GPS and RX/TX is relative to the PC)
For a DB-25 serial connector:
Pin 2: Data Out (RX Data)
Pin 3: Data In (TX Data)
Pin 7: Ground (0V)
As far as I can see the votage level specifications are:-
RS232:
Mark (1): -5 to -15 volt
Space(0): +5 to +15 volt
NMEA 0183:
Mark (1): <0.5 volt
Space (0): >4.0 volt
Another obvious simple [hymenoptera level again :-) ] Google search for
"garmin gps-75 rs232" would point you at a document you could be looking
for on the Garmin website: "GARMIN GPS Interface Specification"
http://www.garmin.com/support/pdf/iop_spec.pdf
General comments (NOT receiver specific) include:
"The default Physical protocol is based on RS-232. The voltage
characteristics are compatible with most Host devices; however, the GPS
transmits positive voltages only, whereas the RS-232 standard requires
both positive and negative voltages. Also, the voltage swing between mark
and space may not be large enough to meet the strict requirements of the
RS-232 standard. Still, the GPS voltage characteristics are compatible
with most Host devices as long as the interface cable is wired correctly."
In other words voltage levels are consistent with the NMEA 0183 standard
but the GPS is designed to safely accept RS232 signals so nothing should
be damaged in either direction.
It's going to be up to you whether you decide to risk it!
David
|
Termites are devious creatures, they let humans build houses for them to
supply the free lunch.
Thanks for your efforts on my behalf.
I imagine I should be able to cobble together something from that, although
I would much prefer the GPS died than the computer. |
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