Hi, Everybody,

I am trying to set up an APRS station consisting of a Garmin GPSmap 60 and
one of the TinyTrak3 TNCs. However, the green 'GPS Valid' LED never lights.

I can connect the GPS receiver directly to my computer's serial port and
read good data, and I can capture some of that data and play it back from
computer to TinyTrak and the green LED lights up, but a direct connection
between GPS and TT just does not work.

I see a waveform coming out of the GPS serial (J2 pin 2 of the TT) using a
scope. Quiescent voltage is -5V, and when the data burst comes it is -5 V to
+5 V.

Could this be a voltage level problem on the serial? Is there a converter
that can be used? Or is it another problem, possibly protocol-related?

Any ideas?

Thank you,

Al W6LX

On Mon, 30 May 2005 17:06:59 -0700, "Anonymous"
wrote:

Hi, Everybody,

I am trying to set up an APRS station consisting of a Garmin GPSmap 60 and
one of the TinyTrak3 TNCs. However, the green 'GPS Valid' LED never lights.

I can connect the GPS receiver directly to my computer's serial port and
read good data, and I can capture some of that data and play it back from
computer to TinyTrak and the green LED lights up, but a direct connection
between GPS and TT just does not work.

I see a waveform coming out of the GPS serial (J2 pin 2 of the TT) using a
scope. Quiescent voltage is -5V, and when the data burst comes it is -5 V to
+5 V.

Could this be a voltage level problem on the serial? Is there a converter
that can be used? Or is it another problem, possibly protocol-related?

Any ideas?

Thank you,

Al W6LX


OK Al, I'm going to go out on a limb here. The GPS doesn't work on
the TNC. It does work on the PC. The PC can send GPS data it
recorded from the GPS out to the TNC and the TNC recognizes the dya as
GPS data and interprets the protocol correctly (the green LED goes
on). You measured the waveform from the GPS and it shows +- 5V.

I. The GPS is good, it works on the PC.
II. The PC is good, it reads and writes GPS data.
III. The TNC is good, it reacts correctly to the PC and the GPS data
from the PC.
IV. The GPS waveform is +- 5V.

My conclusion: The voltage is too small for the TNC to recognize.
Did you 'scope the PS serial data? If you do, you will see that it is
+- 12V. The PC's serial port can read and write both +-5V and +-12V
levels. You need a level converter to change the GPS data to the
level that the TNC needs to see.

Russ

In article , "Anonymous"
wrote:

I am trying to set up an APRS station consisting of a Garmin GPSmap 60 and
one of the TinyTrak3 TNCs. However, the green 'GPS Valid' LED never lights.

Al-

Russ may be right about needing level conversion. Another possibility is
that you need a null-modem adapter in the line between the GPS and the
TNC.

And what about baud rate? What if the PC has automatic baud-rate
adjustment and the GPS & TNC don't?

73, Fred, K4DII

Thanks to all who replied. In the end, I never got it working. It appears to
be a basic incompatibility between the Garmin GPSmap 60 and the TinyTrak3. I
should have done better research into exactly which GPS models are
compatible with the TinyTrak3.

An exhaustive search of the Internet turns up absolutely no information on
incompatibilities between the TinyTrak3 and the vast number of GPS units on
the market today. But neither could I find any complaints of people running
into incompatibility problems. Strange.

Incidentally, the latest generation of Garmin units have only USB ports, no
more serial ports. By definition, all of these are incompatible with the
TinyTrak3.

I have a feeling that the TinyTrak3 hasn't kept up with the times and if it
expects to survive it has to be updated to allow operation with the latest
NMEA protocol version and the new USB units.

The TinyTrak is a good idea. I hope it gets updated, and I hope to see a
section on its web site with information about which GPS's are okay and
which ones to avoid.

Regards,

Al W6LX







"Anonymous" wrote in message
...
Hi, Everybody,

I am trying to set up an APRS station consisting of a Garmin GPSmap 60 and
one of the TinyTrak3 TNCs. However, the green 'GPS Valid' LED never
lights.

I can connect the GPS receiver directly to my computer's serial port and
read good data, and I can capture some of that data and play it back from
computer to TinyTrak and the green LED lights up, but a direct connection
between GPS and TT just does not work.

I see a waveform coming out of the GPS serial (J2 pin 2 of the TT) using a
scope. Quiescent voltage is -5V, and when the data burst comes it is -5 V
to
+5 V.

Could this be a voltage level problem on the serial? Is there a converter
that can be used? Or is it another problem, possibly protocol-related?

Any ideas?

Thank you,

Al W6LX

Al,

"Anonymous" wrote in message
...
I have a feeling that the TinyTrak3 hasn't kept up with the times and if it
expects to survive it has to be updated to allow operation with the latest
NMEA protocol version and the new USB units.

Unfortunately, whereas "RS-232 and NMEA" are very much a standard, the newer
GPS receivers with USB ports neither all show up as a "standard serial-type
device" nor do they encode NMEA the same way. :-( Updating the TinyTrak to
support USB receivers is a _major_ undertaking... whereas you can talk RS-232
with any old microcontroller (especially at the 4800bps that NMEA typically
uses), I believe that the commercial USB receivers are running full speed
(12Mbps) and there is simply no way to build a full speed USB master (what you
need to talk to one of these receivers) in software alone. I.e., the TinyTrak
would have to change to incorporate a microcontroller containing a USB _host_
(and these are few and far between -- Cypress has one), or it would have to
add a separate chip to perform this function.

OEM GPS modules that spit out RS-232 won't be going away any time soon; even
in 2010 you'll still have no problem getting them.

---Joel Kolstad

"Joel Kolstad" wrote in message
...
Al,

"Anonymous" wrote in message
...
I have a feeling that the TinyTrak3 hasn't kept up with the times and if
it
expects to survive it has to be updated to allow operation with the
latest
NMEA protocol version and the new USB units.

Unfortunately, whereas "RS-232 and NMEA" are very much a standard, the
newer
GPS receivers with USB ports neither all show up as a "standard
serial-type
device" nor do they encode NMEA the same way. :-( Updating the TinyTrak
to
support USB receivers is a _major_ undertaking... whereas you can talk
RS-232
with any old microcontroller (especially at the 4800bps that NMEA
typically
uses), I believe that the commercial USB receivers are running full speed
(12Mbps) and there is simply no way to build a full speed USB master (what
you
need to talk to one of these receivers) in software alone. I.e., the
TinyTrak
would have to change to incorporate a microcontroller containing a USB
_host_
(and these are few and far between -- Cypress has one), or it would have
to
add a separate chip to perform this function.

OEM GPS modules that spit out RS-232 won't be going away any time soon;
even
in 2010 you'll still have no problem getting them.

---Joel Kolstad

A lot of GPSs these days have Bluetooth and so practically all PDAs and
almost all notebooks - now all we need is for the radio manufacturers to
include it.
73
Roger ZR3RC

A lot of GPSs these days have Bluetooth and so practically all PDAs and
almost all notebooks - now all we need is for the radio manufacturers to
include it.
===========================
Perhaps there are Bluetooth to serial port RS232 /USB1 /USB2 converters ?

Frank GM0CSZ / KN6WH

"Highland Ham" wrote in message
...
A lot of GPSs these days have Bluetooth and so practically all PDAs and
almost all notebooks - now all we need is for the radio manufacturers to
include it.
===========================
Perhaps there are Bluetooth to serial port RS232 /USB1 /USB2 converters
?

Frank GM0CSZ / KN6WH



USB --- Bluetooth are very common and quite cheap - getting to RS232 might
take a bit more research.

Hi Roger,

"Roger Conroy" wrote in message
...
A lot of GPSs these days have Bluetooth and so practically all PDAs and
almost all notebooks - now all we need is for the radio manufacturers to
include it.

AFAIK, there aren't any simple "microcontroller to Bluetooth" interfaces
available either. I forget the exact chip, but I'm fairly certain the
TinyTrak 3 uses some little 8 bit microcontroller with probably no more than
"many kilobytes" of flash ROM and "a handful of kilobytes" of RAM. That's
nowhere near enough to support Bluetooth.

Bluetooth is also a lot more power hungry than a wired connection would be,
and of course is prone to interference since it's operating in the 2.4GHz ISM
bands.

---Joel

Unfortunately, whereas "RS-232 and NMEA" are very much a standard,

Hi, Joel,

Actually, RS-232 has always baffled me, and from some measurements I made it
doesn't seem to be a very strict standard. For example, the waveform coming
out of the GPS receiver was +/- 5 V, whereas I have seen the waveform out of
the RS-232 on the computer at +/- 12 V. Is the voltage level arbitrary?

Al