Garrett GTI2500 usability mod?

[oroplata]

Greetings,

First post!

The main detector I use is the Garrett GTI2500, for coin hunting.

Unfortunately this detector has only two tone outputs (ignoring the high-conductivity BOING!!! sound) - a "normal" tone for most metals and a lower tone for targets below 3 on their (rather coarse) conductivity scale. This 2-tone setting is not the default, you have to switch on "bi-level" for it to work.

I hunt with discrimination set to zero and bi-level on. I don't use "coin" discrimination as it is set too high for many NZ coins, and anyway it's annoying if you get a ping and then it "disappears" when you do the next sweep because the detector is still picking up the target but it's be re-allocated to a lower conductivity and hence gets blanked.

Even still, because the "bi-level" point is set at conductivity level 3, I have to continuously check the (rather small) conductivity display whenever I get the higher of the 2 tones, and ignore if it is below 4.5 (for conditions here in NZ).

It would be SOOOOOO MUCH better if Garrett allowed the "bi-level" point to be adjusted up to wherever the user wanted it - or maybe even better - made it so the higher the conductivity the higher the tone frequency. That would allow me to walk along listening for the right tone and watch the scenery go by rather than having to continuously look down at the display only to find the target is one I'm not interested in.

But I suspect the chances of them adding this function to the GTI2500 is remote. So I wonder, could I disassemble the code on the 2 socketed ROM's in the unit, and adjust the "bi-level" point myself?

Has anyone here dug into the internals of the GTI2500 to make changes to the microcode?

Is it an easy matter to zero in on the code that runs this feature, or am I taking on something that is extremely tricky to do and I would be better off concentrating on building my own detector so I can have positive input into the feature list?

The thing is, I like the depth indication on the GTI2500 and not sure that's been built into any of the homebrew machines yet?

Comments invited...

[Funfinder]

Hi and welcome here!


They idea you have may not be possible.

You don't have the source-code, Garrett won't give it out, how to compile and program etc.

All you can try (at your own risk) is to reverse-engineer the
display output or more correctly spoken:
trace the LCD signals that create those ID display dots on the screen
and create a high impedance soundchip input for each (or the important ones for you) of them.

That way you can get your own audio ID output.

However I doubt you can do this with usual tools, the connection-wires for LCDs are most of the time way to thin and close together nowadays. But perhaps you can decode and intercept the LCDs chip output (or input) data.

btw. the 2500 is far too heavy!
you should modify it for "hang around the neck"
like I did with the 1500 (incl. coil-cable extension):

http://www.geotech1.com/forums/showp...1&postcount=14

[oroplata]

Hi and welcome here!

Thanks!

They idea you have may not be possible.

You don't have the source-code, Garrett won't give it out, how to compile and program etc.

All you can try (at your own risk) is to reverse-engineer the
display output or more correctly spoken:
trace the LCD signals that create those ID display dots on the screen
and create a high impedance soundchip input for each (or the important ones for you) of them.

That way you can get your own audio ID output.

However I doubt you can do this with usual tools, the connection-wires for LCDs are most of the time way to thin and close together nowadays. But perhaps you can decode and intercept the LCDs chip output (or input) data.

Yeah. The GTI2500 has 3 board stacked one top of each other. I think the LCD data is sent in a header between board 2 and 3 so I might be able to intercept the logic there and analyse it.

A shame though, it would take long for Garrett to burn chips with a different changeover level between the low and high tones, or make it adjustable (rather than just on/off). They're probably not interested in doing that though, since the GTI2500 is probably nearing the end of it's product cycle.

btw. the 2500 is far too heavy!
you should modify it for "hang around the neck"
like I did with the 1500 (incl. coil-cable extension):

http://www.geotech1.com/forums/showp...1&postcount=14

Heh. Yeah it's very heavy, but my wife likes my bulging bicep (only have one - on my detector swinging arm, unfortunately). I still need to have the pinpoint coil though, we have parks here absolutely chock full of silver coins, so no need to go scrabbling up mountainsides looking for metal.

I'm starting to play with the arduino and pulse detector circuits so I'll put the Garrett mod aside and concentrate on building a detector that I can adjust EXACTLY to the conditions we have here.