Thursday, August 20, 2009

APRS tracker (Tinytrak)

After programing the 16F84-4 PIC I placed it on a perforated board and start soldering.
This time no ugly construction technic, only ugly, because there were to many pins to solder on the PIC, this method is easier for this type of circuit.

Schematic and software are here:
Cable connection for my handheld (TH-F7E) from here: (it's also on kenwood manual.) the radio is set as TNC for the external plugs, could be set as speaker, tnc or pc control for programing.

It was not that easy to get data from my GPS (Garmin GPSMAP 60Csx) since the GPS data signal was not being received by the PIC it's the old war between ttl/cmos/rs232/482....whatever incompatibilities :)
So I made an level converter a simple comon emitter with an 2n3904, any npn will work, (incidentally is also an signal inverter) so I could feed the data to the pic. Strange is the on the Garmin side I have to place the ground to data out and data in on the pic to ground..., is Garmin wrong on the manual? It's the pic software or it's because of the inverter circuit.... should work on other gps without inverter so it's not on software.... oh well...

The LM7805 gets a little bit hot for my taste so will lower the input voltage putting another regulator that way I will get the same dissipation but will be divided by 2 devices. Eventually will be powered by a 7.2v source.

Programing was almost flawless except for a small short between tracks on the board that was not letting me to read or write the PIC.
The software was "TTconfig 1.3" but had to install some perl modules needed:
Tk::TFrame and Time::HiRes
basically nothing more that issuing the following command: perl -MCPAN -e shell
and then this one: install Tk::TFrame
and: install Time::HiRes
questions? the INSTALL file on TTConf-1.3

Made some testing tone transmissions, looks clean althoug only tested with the tone features, as soon as I remove the pc interface will place the gps input again. next time I will place a 9 ping plug because it's easier than soldering the cables for testing.

Now it's just to put it on a box get a data plug for the Garmin unit and start beaconing aprs... will use the rest of the perforated board (it was expensive 6.12€ for a 100*160mm, used about 1€ on the tracker) for an aprs packet decoder.... but that's for another day.

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