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EEVblog => Other Blogs => Topic started by: Perrin21 on August 07, 2019, 07:59:27 am

Title: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Perrin21 on August 07, 2019, 07:59:27 am
Hi, does anyone know which multimeters are using the STM32 Microcontroller?  I have recently been testing one out (a multimeter based on this micro) and wondered how common this microcontroller is in DMMs.  I have noticed there is a large hacking community for these microcontrollers and have just watched Dave's STM32 video showing how the chips can be reprogrammed.  Could this be the ultimate hackable DMM?  or am i barking up the wrong tree and its quite common? Its not what i expected to find when i tore it apart.

Review here https://youtu.be/xRkMdbNCBWo
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 07, 2019, 08:39:10 am
Hi, does anyone know which multimeters are using the STM32 Microcontroller?  I have recently been testing one out (a multimeter based on this micro)

I don't know any, but you can tell more about the one you tested. PCB pictures will help too.

Quote
I have noticed there is a large hacking community for these microcontrollers

Any pointers to stm32 *hacking* community?
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 07, 2019, 09:42:39 am
That's interesting.  I have one here.  Very cool.  That should at least make the teardown more interesting.  Will share more details very soon, I'm just working on the video now.  Could be a nice hackable meter then :) 1000V Cat 4 too.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 07, 2019, 09:54:45 am
here is a teaser
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 07, 2019, 11:11:57 am
here is a teaser

Teaser? :) Can't you tell make and model of multimeter? Yes, indeed there is stm32 inside. So what? Most likely you can't read-out it's firmware anyway (unless you are ready to invest significant amount of money). It means no *hacking*. You have to swap chip on PCB with new one and *develop* stm32 code from grounds-up. Before that you have to reverse-engineer and analyze circuit of device to fully understand it's operation so you can write code that actually works. All that for what exactly? - To prove that you can do it? Good luck with that. I mean it.

"Improvement"of instruments is recurring topic here. Most of those who actually want to use instruments will just use them as is. Serious engineer do not want to debug device he is building with tool he can't rely-on, that needs to be debugged itself.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Kean on August 07, 2019, 11:16:06 am
Hi, does anyone know which multimeters are using the STM32 Microcontroller?

You know that Dave's 121GW DMM uses an STM32L152 don't you?
Title: Re: Which multimeters use the STM32 Micro?
Post by: 001 on August 07, 2019, 11:55:03 am
here is a teaser

Why so pathetic? It is only EE forum
Title: Re: Which multimeters use the STM32 Micro?
Post by: ebastler on August 07, 2019, 12:14:41 pm
here is a teaser

Yeah, man, you have uncovered the ultimate business model. Buy those secret multimeters, hack them up to 10 times better resolution and add an on-board Tetris game, then sell them for twice the price. Better make sure nobody figures out the DMM brand!

 ???
Title: Re: Which multimeters use the STM32 Micro?
Post by: coromonadalix on August 07, 2019, 12:20:42 pm
Why double posting  in the microcontroller section ? 

Annoying to say the least.  thread removed
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 07, 2019, 01:27:15 pm
As we know that Dave's DMM uses this exact stm32 kind, it could be Brymen 869S? Other option would be Megger AVO835?
Title: Re: Which multimeters use the STM32 Micro?
Post by: coromonadalix on August 07, 2019, 03:24:56 pm
Another going nowhere thread .......  unless Perrin21  show us a video of photo(s) or model name and brand,  this thread should stop here.



Title: Re: Which multimeters use the STM32 Micro?
Post by: gamalot on August 07, 2019, 04:36:29 pm
EEVBlog 121GW  :)
Title: Re: Which multimeters use the STM32 Micro?
Post by: MosherIV on August 07, 2019, 09:16:57 pm
I think the Fluke 287/289 both use an STM32F of some kind.

How hackable are they?
Firstly, someone has already mentioned that the firmware is likely to be protected, it is near impossible to read out.
Secondly, there are over 100 variants of the STM32F line of micros. Even if you know the specific micro, with all the peripheral options,  knowing what all the io pins are doing means reverse engineering the entire circuit.
Thirdly, The original source code is likely to be in high level language like C. So the amount of binary/assembly code is likley in 100s Kbytes. Then you have compiler optimisation to get your head around.

Simple answer - not very. Only the really, really, really, really determined will even try!
Title: Re: Which multimeters use the STM32 Micro?
Post by: gamalot on August 07, 2019, 11:35:59 pm
I think the Fluke 287/289 both use an STM32F of some kind.

How hackable are they?
Firstly, someone has already mentioned that the firmware is likely to be protected, it is near impossible to read out.
Secondly, there are over 100 variants of the STM32F line of micros. Even if you know the specific micro, with all the peripheral options,  knowing what all the io pins are doing means reverse engineering the entire circuit.
Thirdly, The original source code is likely to be in high level language like C. So the amount of binary/assembly code is likley in 100s Kbytes. Then you have compiler optimisation to get your head around.

Simple answer - not very. Only the really, really, really, really determined will even try!

MCU used in Fluke 287/289 is MSP430 from TI:

https://www.eevblog.com/forum/reviews/fluke-287-dmm-teardown-and-photos/ (https://www.eevblog.com/forum/reviews/fluke-287-dmm-teardown-and-photos/)
Title: Re: Which multimeters use the STM32 Micro?
Post by: Mr. Scram on August 07, 2019, 11:42:16 pm
Guess what I had for supper last night? I'm not going to tell you but I'll give you a hint. It came on a plate.
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 08, 2019, 01:01:15 am
Guess what I had for supper last night?

You think we want to know but whole sensation of revelation is just your illusion
Title: Re: Which multimeters use the STM32 Micro?
Post by: Mr. Scram on August 08, 2019, 07:01:29 am
You think we want to know but whole sensation of revelation is just your illusion
Considering the number of revelation teaser threads lately that can't be right.
Title: Re: Which multimeters use the STM32 Micro?
Post by: DaJMasta on August 08, 2019, 06:21:28 pm
Guess what I had for supper last night? I'm not going to tell you but I'll give you a hint. It came on a plate.

Fancy schmancy, you didn't have to eat it off some wax paper/paper bag?


I also don't understand the secrecy.  As far as I know, every STM32 is reprogrammable, so it would be hackable with commonly available tools.  Also not uncommon among meters, it's a fairly standard, fairly good, fairly cheap micro from a reputable brand name, and it makes for a good light-duty low power application processor.
Title: Re: Which multimeters use the STM32 Micro?
Post by: blueskull on August 08, 2019, 06:24:53 pm
MCU used in Fluke 287/289 is MSP430 from TI:

Yup. And F289 was once regarded as an excellent design using off the shelf perts (rest of a custom part made by LT).

And I believe F289 was born before STM32.
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 08, 2019, 06:55:13 pm
You think we want to know but whole sensation of revelation is just your illusion
Considering the number of revelation teaser threads lately that can't be right.
Teaser of revelation does not guarantee that it will be delivered in the end. That's actually The Point.
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 08, 2019, 07:06:15 pm
As far as I know, every STM32 is reprogrammable, so it would be hackable with commonly available tools.

Incorrect. Read-out protection level-2 disables all debug interfaces leaving only bootloader as means for reprogramming. If bootloader is vendor-specific or what's worse - uses firmware encryption, you are out of luck reusing such stm32 IC especially "with commonly available tools".
Title: Re: Which multimeters use the STM32 Micro?
Post by: MosherIV on August 08, 2019, 08:23:54 pm
Quote
As far as I know, every STM32 is reprogrammable, so it would be hackable with commonly available tools.
If by 'hackable' you mean wipe and re-program from scratch. Yes.

If you mean read out and modify single bytes to modify the existing program -  :palm:
NO.

I refer you to ogden's comment and if you manage to read out the existing code I refer you to my ealier post
Quote
Secondly, there are over 100 variants of the STM32F line of micros. Even if you know the specific micro, with all the peripheral options,  knowing what all the io pins are doing means reverse engineering the entire circuit.
Thirdly, The original source code is likely to be in high level language like C. So the amount of binary/assembly code is likley in 100s Kbytes. Then you have compiler optimisation to get your head around.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Nornand on August 08, 2019, 08:50:53 pm
Hacking a secured STM32FO

https://www.aisec.fraunhofer.de/en/FirmwareProtection.html (https://www.aisec.fraunhofer.de/en/FirmwareProtection.html)
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 08, 2019, 09:07:11 pm
Hacking a secured STM32FO

https://www.aisec.fraunhofer.de/en/FirmwareProtection.html (https://www.aisec.fraunhofer.de/en/FirmwareProtection.html)

To do the "hacking", in this case flash readout, protection level must be downgraded from RDP2 to RDP1 using UV EEPROM eraser on previously decapsulated chip. It can't be considered as "reprogramming with commonly available tools" :)

Quote
As far as I know, every STM32 is reprogrammable, so it would be hackable with commonly available tools.
If by 'hackable' you mean wipe and re-program from scratch. Yes.

No. You can't wipe nor reprogram RDP2-protected stm32.
Title: Re: Which multimeters use the STM32 Micro?
Post by: MosherIV on August 10, 2019, 09:54:46 am
Quote
No. You can't wipe nor reprogram RDP2-protected stm32.
I have not worked with ST parts now for more than 5 years but I thought that using SWD/JTAG to disable RDP2 would result in wiping the flash and hence allow reprogramming. My bad if I am wrong.
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 10, 2019, 10:34:17 am
Quote
No. You can't wipe nor reprogram RDP2-protected stm32.
I have not worked with ST parts now for more than 5 years but I thought that using SWD/JTAG to disable RDP2 would result in wiping the flash and hence allow reprogramming. My bad if I am wrong.

How could you disable RDP2 with SWD/JTAG when main function of RDP2 is to disable SWD/JTAG?!  :-DD
Title: Re: Which multimeters use the STM32 Micro?
Post by: Mr. Scram on August 10, 2019, 01:22:51 pm
Did we get an answer from OP yet? If not it's time to close the thread.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Kean on August 10, 2019, 03:25:09 pm
Did we get an answer from OP yet? If not it's time to close the thread.

I presume you mean the "answer" to the teaser?

Because OP's original question has been answered: it is somewhat common, and without more info I suspect the EEVblog 121GW is most likely more hackable due to the published schematic and microSD slot.
Plus, some significant work has already been done on reverse engineering the 121GW beyond the schematic ... https://github.com/tpwrules/121gw-re

If you just want a well documented multimeter circuit to hack into your own design, then Digilent have this https://store.digilentinc.com/dmm-shield-7-function-digital-multimeter-shield/
Title: Re: Which multimeters use the STM32 Micro?
Post by: ebastler on August 10, 2019, 03:46:51 pm
Did we get an answer from OP yet? If not it's time to close the thread.

No, the OP hasn't been back on EEVblog since three days. Busy building his new multimeter business, or turning his scoop into a full-length movie, I presume.  ::)
Title: Re: Which multimeters use the STM32 Micro?
Post by: CDaniel on August 11, 2019, 08:03:47 am
For a fully functional multimeter with a mature firmware , what is the point for "hacking" ? You can't add features or improve it . The 121GW , as it is now , is not used to the max and has some deficiencies, that why the haching and improving the firmware could be very usefull .
Title: Re: Which multimeters use the STM32 Micro?
Post by: coromonadalix on August 12, 2019, 07:23:04 am
Seems this meter,   a video has been made

https://www.eevblog.com/forum/testgear/ive-reviewed-the-megger-avo835-this-feels-like-it-fell-under-the-radar/new/#new (https://www.eevblog.com/forum/testgear/ive-reviewed-the-megger-avo835-this-feels-like-it-fell-under-the-radar/new/#new)
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 12, 2019, 07:39:03 am
Yes, well-made video.  :-+
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 10:06:17 am
Yes, well-made video.  :-+
Thanks, im very new to all this.  Glad you liked it.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 10:09:16 am
Did we get an answer from OP yet? If not it's time to close the thread.

No, the OP hasn't been back on EEVblog since three days. Busy building his new multimeter business, or turning his scoop into a full-length movie, I presume.  ::)

Haha, you have no idea.  Filming and editing the video has been non stop for the full week.  Even deciding if i should just do a basic unboxing or go into deeper depth wasn't easy to decide as you can see from some of the comments here.  I have been editing for 5 days solid and the result is a 12 min video lol.  Don't know how most youtubers manage to release content so fast. 
Title: Re: Which multimeters use the STM32 Micro?
Post by: Black Phoenix on August 12, 2019, 10:13:39 am
Haha, you have no idea.  Filming and editing the video has been non stop for the full week.  Even deciding if i should just do a basic unboxing or go into deeper depth wasn't easy to decide as you can see from some of the comments here.  I have been editing for 5 days solid and the result is a 12 min video lol.  Don't know how most youtubers manage to release content so fast.

We can talk again one year from now when you released a lot more videos... With time you will start getting shortcuts and knowing where everything is plus improving your workflow.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 10:13:58 am
Did we get an answer from OP yet? If not it's time to close the thread.

I presume you mean the "answer" to the teaser?

Because OP's original question has been answered: it is somewhat common, and without more info I suspect the EEVblog 121GW is most likely more hackable due to the published schematic and microSD slot.
Plus, some significant work has already been done on reverse engineering the 121GW beyond the schematic ... https://github.com/tpwrules/121gw-re

If you just want a well documented multimeter circuit to hack into your own design, then Digilent have this https://store.digilentinc.com/dmm-shield-7-function-digital-multimeter-shield/

In many ways this was the scope of the question, to establish if id found gold or tin.  I haven't taken apart enough meters to know if the STM32L152 is common amongst them or if its a rarer find.  I also come from more of a hacking background so like to tweak things to do things they shouldn't.  Someone joked about Tetris, i have a remote control I've made do that already lol.  Even making it flash on continuity would be useful to someone.  I think id feel warm inside if i powered it up and it said PWND but hey, its the little things. 

I think you can see from my video and the way i went about it that i didn't want to make just another multimeter video (even if some would have preferred that) because it isn't me.  I prefer to try and find out what something can't do rather than just see what it already does. 
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 10:22:16 am
here is a teaser

Teaser? :) Can't you tell make and model of multimeter? Yes, indeed there is stm32 inside. So what? Most likely you can't read-out it's firmware anyway (unless you are ready to invest significant amount of money). It means no *hacking*. You have to swap chip on PCB with new one and *develop* stm32 code from grounds-up. Before that you have to reverse-engineer and analyze circuit of device to fully understand it's operation so you can write code that actually works. All that for what exactly? - To prove that you can do it? Good luck with that. I mean it.

"Improvement"of instruments is recurring topic here. Most of those who actually want to use instruments will just use them as is. Serious engineer do not want to debug device he is building with tool he can't rely-on, that needs to be debugged itself.

All good points and i don't disagree with anything you have said.  I wasn't looking to offend with the term Teaser.  Please allow me some intrigue for the efforts I've made to make a video review of a meter that isn't commonly known.  I hope you  have enjoyed the video and at least its a tiny bit more insight than the community otherwise had into this product.  My channel isn't monetised as i don't have enough subscribers or views yet so this is a lot of work for no financial reward (over a weeks worth).  Im hoping i can make content that gets views over time rather than just over the first few days.  Its an early first effort at doing a proper review and promoting it.  Don't be too harsh lol.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 10:27:53 am
Did we get an answer from OP yet? If not it's time to close the thread.

No, the OP hasn't been back on EEVblog since three days. Busy building his new multimeter business, or turning his scoop into a full-length movie, I presume.  ::)

No multimeter business, just trying to make a youtube channel worth watching.  I guess i didn't realise how tough the audience is lol.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 10:30:12 am
Haha, you have no idea.  Filming and editing the video has been non stop for the full week.  Even deciding if i should just do a basic unboxing or go into deeper depth wasn't easy to decide as you can see from some of the comments here.  I have been editing for 5 days solid and the result is a 12 min video lol.  Don't know how most youtubers manage to release content so fast.

We can talk again one year from now when you released a lot more videos... With time you will start getting shortcuts and knowing where everything is plus improving your workflow.

My experience of Final Cut Pro is this one video, im learning as i go.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 12, 2019, 06:15:25 pm
Did we get an answer from OP yet? If not it's time to close the thread.

Here is the answer you desire https://youtu.be/xRkMdbNCBWo
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 12, 2019, 06:41:45 pm
Im hoping i can make content that gets views over time rather than just over the first few days.  Its an early first effort at doing a proper review and promoting it.  Don't be too harsh lol.

No worries. Production quality is very good, well above average in the category. Looks like expensive enough commercial :) Impressive start. Hope that you have next trick in your sleeve already.
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: CDaniel on August 12, 2019, 07:26:05 pm
Video is good , but implying is a competitor or somewhat equivalent to Fluke 87-V is  a little farfetched if you look at the specs ... I don't think you will get many viewers with such exaggerations  :)
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Perrin21 on August 12, 2019, 07:42:47 pm
Wow that's some compliment for my first proper video.  Thanks, glad you liked it.  I had an idea in my head how i wanted it to look but once you start adding flashy FX it does start to look like an advert lol.  I tried to rein it back in but i also wanted it to look as professional as possible as im trying to improve my production quality as time goes forward.  This video literally felt like it took an age to make but its worth it if people like it.  I have seen loads of other DMM videos and many are a lot more technical than i was able to get so i made up for that with 4K and some additional info.  Glad you liked it, hope you subscribe.
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Perrin21 on August 12, 2019, 07:47:41 pm
Video is good , but implying is a competitor or somewhat equivalent to Fluke 87-V is  a little farfetched if you look at the specs ... I don't think you will get many viewers with such exaggerations  :)

I wasn't trying to exaggerate.  Its clear that's what the Product is targeting even if it may fall short in some areas.  I have made clear comparisons in the video where they have even appeared to copy some of the Fluke design.  I would say the input protection is every bit as good as the Fluke 87V and the board is much more modern in its design and layout.  I never gave it a 10 star review and i have been critical in the areas i could see where it fell short.  I couldn't put everything or the video would be twice as long and it would have lost the viewer.  I watch it and know there were things i forgot to mention but once its up its up.   Megger is a very reputable brand here in the UK, every bit as reputable as Fluke and they specialise in much more expensive equipment than the DMM i reviewed.  In many ways its a small device to them in the big machine that is Megger.
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Grandchuck on August 12, 2019, 08:19:18 pm
Damn good video!  Can't wait to see what else you come up with.
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Perrin21 on August 12, 2019, 08:26:32 pm
Damn good video!  Can't wait to see what else you come up with.

Maybe I will even surprise myself, thanks. 
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: CDaniel on August 12, 2019, 08:49:57 pm
Video is good , but implying is a competitor or somewhat equivalent to Fluke 87-V is  a little farfetched if you look at the specs ... I don't think you will get many viewers with such exaggerations  :)

I wasn't trying to exaggerate.  Its clear that's what the Product is targeting even if it may fall short in some areas.  I have made clear comparisons in the video where they have even appeared to copy some of the Fluke design.  I would say the input protection is every bit as good as the Fluke 87V and the board is much more modern in its design and layout.  I never gave it a 10 star review and i have been critical in the areas i could see where it fell short.  I couldn't put everything or the video would be twice as long and it would have lost the viewer.  I watch it and know there were things i forgot to mention but once its up its up.   Megger is a very reputable brand here in the UK, every bit as reputable as Fluke and they specialise in much more expensive equipment than the DMM i reviewed.  In many ways its a small device to them in the big machine that is Megger.

A small advice ... you have to be impartial to be succesfull in this area , I see that you a very big Magger's fan  ;D , or they pay you to do it .
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Perrin21 on August 12, 2019, 09:40:47 pm
Video is good , but implying is a competitor or somewhat equivalent to Fluke 87-V is  a little farfetched if you look at the specs ... I don't think you will get many viewers with such exaggerations  :)

I wasn't trying to exaggerate.  Its clear that's what the Product is targeting even if it may fall short in some areas.  I have made clear comparisons in the video where they have even appeared to copy some of the Fluke design.  I would say the input protection is every bit as good as the Fluke 87V and the board is much more modern in its design and layout.  I never gave it a 10 star review and i have been critical in the areas i could see where it fell short.  I couldn't put everything or the video would be twice as long and it would have lost the viewer.  I watch it and know there were things i forgot to mention but once its up its up.   Megger is a very reputable brand here in the UK, every bit as reputable as Fluke and they specialise in much more expensive equipment than the DMM i reviewed.  In many ways its a small device to them in the big machine that is Megger.

A small advice ... you have to be impartial to be succesfull in this area , I see that you a very big Magger's fan  ;D , or they pay you to do it .

No not a fan of the brand as such.  I used to have an old AVO2007 when I was 10 that was handed down from a close family member and always loved its industrial design.  That was a Metrawatt device they branded.  I was recently looking for a new meter myself and started my research here then during my search I thought id check out Megger after trying to find the modern replacement for my old AVO.  If you search my posts here you will find that.  I then settled on the Yokogawa meter as it felt closest to my aspiration in industrial design but Joe Smith put me off it with his review when it didn't register dangerous voltages.  So I decided to take advice given here and got the Brymen 869S which I am very pleased with.  I later looked into the Megger AVO835 some more as I liked the look of it but I couldn't find any reviews of it on YouTube bar 1 which was just an unboxing.  After talking with Joe he suggested I do my own review of it as I was curious still so the rest is history.  I like the device and I had very high hopes for it as its British designed, the more I dug I to it the more I liked it.  Is it perfect? no, but its still a nice meter that shouldn't be ignored.  My Channel is very new and it's not even monetised, I've made the extra effort in case another brand wants me to check out their gear so I can build my channel.  I 100% agree about being impartial, you think they would pay me to chuck their probes in the bin and slate their accessories? I live in Brexit Britain and wanted to see what we had to offer in the space, I wasn't dissapointed with the meter itself, inside its a work of Art.
Title: Re: Which multimeters use the STM32 Micro?
Post by: Perrin21 on August 13, 2019, 06:09:16 am
Quote
No. You can't wipe nor reprogram RDP2-protected stm32.
I have not worked with ST parts now for more than 5 years but I thought that using SWD/JTAG to disable RDP2 would result in wiping the flash and hence allow reprogramming. My bad if I am wrong.

how do we know they bothered to encrypt it?
Title: Re: Which multimeters use the STM32 Micro?
Post by: ogden on August 13, 2019, 06:46:59 am
Quote
No. You can't wipe nor reprogram RDP2-protected stm32.
I have not worked with ST parts now for more than 5 years but I thought that using SWD/JTAG to disable RDP2 would result in wiping the flash and hence allow reprogramming. My bad if I am wrong.

how do we know they bothered to encrypt it?

Solder debug connector, connect debug adapter and check using stm32 debugger or st-link utility - MCU responds to debug interface or not (debugger can ID chip). Be careful doing that - do not execute erase. Such error will brick your device.
Title: Re: Which multimeters use the STM32 Micro? Ive just reviewed one.
Post by: Perrin21 on August 14, 2019, 12:53:31 pm
excellent well that confirms what I had planned anyway.  let's see what happens. Daves video on the STM32 micro was very interesting