Let's make a closely MXT like detector!

[KRinAZ]

The original MXT board used an OTP chip that was read-protected. It was updated when I worked there to use a later version chip (for the MXT Pro) that could be reprogrammed, but it was still read-protected. It is possible to defeat the read protection and extract the code but it's a complicated process. An easy solution is to send the board to China and one of the hacker houses will send you back the extracted binary, but it costs around $500. Might be able to find someone who will do it cheaper. The binary can be decompiled to assembly language and then maybe AI can clean it up and even convert to C.

The Chinese cloned the GMT which uses almost the exact same circuitry and mostly the same code as the MXT. It's possible the GMT clones are not protected. In any case, they are a lot cheaper to buy and cannabalize. But if you want to extract the code with them most features, it would be the MXT Pro or the MX Sport.

The original MXT was developed by Dave Johnson and all the code was written in assembly language. There were a lot of fudge factors in the code, often with the comment "this seems to work." I had a co-op student convert all the code to C and port it to an STM processor -- that was released as the MX5, and later used in the MX Sport and GM24K models.

Hey thanks Carl for all this info! In terms of actual field performance how does the MXT Pro compare to the MXT - Prospecting mode, hot soil? I actually used a MX Sport briefly and it was interesting, certainly different from the MXT, I didn't have it long enough to really get in the groove with it though...

Wow I didn't know about all the detector cloning going on, guess maybe due to having blissfully lived so far without an account on aliexpress...but I suppose I'm not surprised...I think I would prefer to ignore the clones and focus on how the real MXT operates...what a purist, eh!

There's a local fellow looking to sell a nice condition MXT Pro... ...so pls let me know your thoughts on the MXT Pro...and is there a way to spot a clone?

Wonder what the controller chip part number is in the Pro? Would like to go over it's datasheet.

[Carl-NC]

The MXT Pro has identical performance to the MXT, it just adds tone ID, ground grab, and a backlight. The GMT was cloned because it had huge sales in Africa, the MXT was never cloned. I'll dig around and see if I can find what micro the Pro used.

[KRinAZ]

The MXT Pro has identical performance to the MXT, it just adds tone ID, ground grab, and a backlight. The GMT was cloned because it had huge sales in Africa, the MXT was never cloned. I'll dig around and see if I can find what micro the Pro used.

Very good, many thx for the Pro info, hope you can find the micro number.

It's interesting that Dave Johnson coded in assembly, didn't know that. I often felt like the odd one using assembly but I guess micro coders probably did so to keep their code as tight and small as possible. It can be hard to fit code and all the features desired into 8k or so of micro code space...

I have another application for this project - a sort of hand held version - hand held coil with ergo hand grip (maybe with display) on the 4x6 DD Shooter, control box on the belt, useful for scanning hard rock gold mine walls & ceiling. I have 2 tunnels and numerous cuts that I want to scan...a full size detector has proven quite awkward for this.

[KRinAZ]

The MXT Pro has identical performance to the MXT, it just adds tone ID, ground grab, and a backlight. The GMT was cloned because it had huge sales in Africa, the MXT was never cloned. I'll dig around and see if I can find what micro the Pro used.

If it helps any, in that pic that ivconic posted of a MXT PCB (probably a later revision PCB) I'm guessing it to have a 28 pin PDIP MicroChip PIC16F886 - but not sure as it's number stamp is not clear when zooming in...pretty sure ivconic found the pic on the web, and so probably doesn't have clearer pics...

[ivconic]

I was surprised when I found a schematic in my archive! I don't remember where I got it from.

[ivconic]

Or like this:

[ivconic]

MXT & GMT, approx 60-70% of the layouts are quite the same.

[KRinAZ]

I was surprised when I found a schematic in my archive! I don't remember where I got it from.

Wow, and I am beyond surprised - I didn't think we'd be so lucky as to have the schematic! Nice job, well done, thanks for posting to you and it's source. It's a wealth of information and ideas for this project. Now a zip of the C would make the complete set haha...

Earlier this evening I ordered Carl's ITMDv3, and George's Arduino Nano VLF Project books from amazon and look forward to absorbing them and applying them to this project. They should arrive Fri 4/17. I plan this week to open up my MXT and see what rev board I have and which micro. I'm also working on acquiring a MXT Pro to dissect, so I'll be doing research and posting insights.

If I find that the MXT Pro has a newer PIC16Fxxx with flash program storage I think I might know how to pull the code...would be a great source of examples and ideas...

[KRinAZ]

MXT & GMT, approx 60-70% of the layouts are quite the same.

Interesting to compare the 2, also interesting the information present on the MXT board e.g. looks like the connector near the center marked P00 (I'm guessing) goes to the display, and if so that it's probably a SPI link, and that the toggle switch under the display probably also goes through that link (still guessing) - update - after looking at the schematic and PIC16C76 data sheet, looks like neither I2C nor SPI is used, but some unique coded serial method (still guessing though).

[Altra]

Here is a look at the pod. It uses a 74164 shift register for a serial to parallel convertor to drive the 16 x 2 LCD. You can also see a 555 timer and a CD4051 multiplexer.

Thanks for the schematic Ivica!

[Skippy]

[deleted]

[Altra]

A partial schematic of the Makro Racer was posted here on the forum a while back. One of the members here claimed it was a copy of the MXT. Looking at the two schematics the Nokta engineer did duplicate many parts from the MXT.

Makro Racer

[Carl-NC]

If it helps any, in that pic that ivconic posted of a MXT PCB (probably a later revision PCB) I'm guessing it to have a 28 pin PDIP MicroChip PIC16F886...

That was an interim replacement for the 16C76, I think prices were going up so we swapped out for another chip.

Post #22 shows the old-style MXT/GMT board on the left, and the new style MXT/MXT Pro/GMT on the right. I switched all the caps and connectors to SMT, the processor is a 44pin QFP, and there is a new PCI edge connector for manufacturing. Sorry, don't know which micro, still a 16F PIC though.

[Carl-NC]

A partial schematic of the Makro Racer was posted here on the forum a while back. One of the members here claimed it was a copy of the MXT. Looking at the two schematics the Nokta engineer did duplicate many parts from the MXT.

The Racer was a hardware clone of the Teknetics T2, except that the T2 used and MSP430 and the Racer has a PIC24. The T2 was designed by David Johnson after he did the MXT, so it was basically an "MXT-2". That's why the Racer looks a lot like the MXT.

[Altra]

The Racer was a hardware clone of the Teknetics T2, except that the T2 used and MSP430 and the Racer has a PIC24. The T2 was designed by David Johnson after he did the MXT, so it was basically an "MXT-2". That's why the Racer looks a lot like the MXT.

That's interesting to know. Looking at the MXT schematic it shows a cycle time of 4ms for the adc. Would that be a single sample or for all the channels?