Reverse Engineering TDS2CM/TDS2MM

[SoloTek]

Would it be possible to upgrade the low-cost module later on by populating the missing componets? Perhaps I find an UART somwhere in my scrap bin 

Btw, how do you emulate a GPIB controller with less than 8 product terms? (if I read the ATF16LV8 correctly?)

Thanks!

[sd_tony]

Mine is 1.04 for both as well.

[sd_tony]

Would it be possible to upgrade the low-cost module later on by populating the missing componets? Perhaps I find an UART somwhere in my scrap bin 

Btw, how do you emulate a GPIB controller with less than 8 product terms? (if I read the ATF16LV8 correctly?)

Thanks!

That is possible, actually the PCB version of the "low-cost" module is V2.2, it can be a full functional module, or a math only module (without communication), depends on the firmware in PLD.

To emulate a GPIB, you don't have to create a full functional controller, instead, you just need to know which register the scope is looking at during boot, and send the valid data back when scope is reading that register, in this way, scope will believe GPIB does exist, and with no slave device connected. Same thing can be done for UART controller, that is why the UART controller can be omitted on the math only module (or "low-cost" module).

[uski]

TDS200 series could be one of the most popular scopes for beginners and hobbyists, there are still lots of used one available and are affordable for beginners, however, the monochrome display with 320x240 display is kind of outdated, an extension module (TDS2CM or TDS2MM) is needed to have RS232/Centronics/GPIB interfaces to send data to PC for better vision/processing

My first scope was a TDS210 with a TDS2MM. It was great, back in 2000.

But today, realistically ? They have abysmal sample memory size (2500 points per channel), lack many features such as protocol decoding, only have an 8 bit ADC, as you mention the LCD is pure crap, and even the FFT sucks. USB communication was slow as hell, I remember screenshots were taking a while and I had to simulate a printer. Their firmware cannot be updated (although I agree, there are little to no bugs - but there are also no features...), and they have their quirks (common issue is a hardware failure of the BNC ports).

I don't want to discourage the effort by any means as I love to read about my first scope and see creative projects, but I really wanted to warn beginners - the going price is around $150-200 these days, apparently.

Even at this price, there are better options like a Hantek DS2C10 ($189, yeah it has some bugs, but so many more features, can be modded, same bandwidth and higher if you mod it, integrated basic AWG for $20 more, USB host for screenshots, it's a new scope and not a 20 years old unit that can start to have its CCFL-backlit display failing ...), and with only a bit more you can get a Rigol DS1054Z or a Siglent which is even one step higher.

I would not advise a beginner to buy a TDS210/TDS220 these days... I would not call it the perfect beginner scope in 2022... Just wanted to share a contrasting opinion.

Now, let's go back to the TDS2CM/MM.

[TERRA Operative]

You certainly can upgrade the firmware.
Well, on the earlier models at least, all you need is a chip programmer and a replacement PROM chip.

I'm still figuring out how on the late model ones that use flash memory, but I need to get my hands on more of those to play with.

[uski]

Ah yeah that's right. I had two boards on hands for my scope. One of them was an earlier revision and looked very different than the later revision.
If I recall properly, the first one used PLCC chips while the other one used SMT chips. Maybe they also switched from EPROM to FLASH too.

[mtk]

And why you haven’t published the final TDS2CM/TDS2MM module schematic and PLD image files ? 88.27 USD (shipping included) for TDS2CM/TDS2MM module with USB seems quite a lot, considering that whole oscilloscope is sold for around 100 USD. To mention not that a WiFi edition can be made.

[coromonadalix]

Check their "original" pricing  ....   on fleabay  and the most ridiculous prices for some of them  loll   you have one in the 300$ range ?

[mtk]

My point is different. This person sd_tony created this topic - Reverse Engineering TDS2CM/TDS2MM. Posted one schematic that is marked as: not complete nor correct and stated look I am selling those modules on eBay. I do not think that this is correct practice and it is kind of misleading that actually this topic provides any useful data or information.

[coromonadalix]

good point,  if  the OP  got help here to built / decode the original(s) modules and sell them ....

We've been had in a way ...

[sd_tony]

This module is way complicated to make than what you thought, I ended up bought two TDS2CM modules with $100+ each, and reverse engineered them completely by myself, please remember that you will need to decode the PLD on the original module, and find out what exactly the firmware is doing during scope boot and during RS232 communication, the 1st TDS2CM module was broken after too many experiments, and I have to bought another one to continue my project.

Picture attached is the 1st prototype I made to verify the concept, as you can see that there are lots of blue-wire to correct the mistake and verify the solution. I can give you an example how difficult to debug the issue encountered: after the module finally can be recognized by scope, the communication with PC is not stable somehow, sometimes it can be identified by PC, sometimes not, that frustrated me a lot. After weeks of debug, it ended up that the UART transceiver (SCN68681) has a limitation which requires the serial resistance of 3.6864M crystal to be <180 ohm and the shunt capacitance to be < 15pF, otherwise the oscillator may have power-up failure. after trying couple of different type of 3.6864M crystals, I finally found one that perfectly meet the requirements.

After this issue got resolved, I realized that this module is component depended (PLD and UART transceiver etc.), it can't be simply reproduced with schematic and PLD firmware, if somebody want to create one as what I did, he may encounter different issues which I may not be able help because I don't the exactly same hardware he has, not even mention that it's not worth to just make one module from cost perspective.

[mtk]

@sd_tony

In my opinion your concept is wrong. This whole module including the PROM and RAM can be emulated on fast MCU like ESP32 and have additional capabilities like WiFi, Bluetooth, USB connectivity as well as internal storage on SD card.

It is disappointing that some prefer to keep their findings instead to share with the community and make better projects.

On the other hand, currently there are much better offers on the market. For example, I found recently an offer for Owon SDS 7102V - 155 €, large color display, USB, Ext, LAN, VGA even possibility to use an internal battery.

[Fieroluke]

Interesting thread!

Inside the TDS2000C series there is an unpopulated 50 pin connector that could be installed, and I assume the pinout is probably at least compatible.
Since the B-version firmware works on the C-series, I wonder if the old expansion modules would be recognized.
For instance adding a printer or serial or gpib. I know the 2000C has USB, but I’m curious…