Hacking the UNI-T UT71C (WIP/Need help) - Page 1
Forum section: electronics / testgear

author: XOIIO
author_rank: Super Contributor
timestamp: May 08, 2014, 05:43:02 am
content: Hello all, my shiny new UNI-T UT71C came in the mail, a 40,000 count multimeter with 100 points for dataogging internally, and as soon as I got it my urge for hacking started to itch. Aside from wanting to do a fuse mod in the future to put HRC fuses in, I want to possibly upgrade this to it's bigger brother the UT71D, which is identical, aside from having 10,000 data logging points internally, and I figured the boards will be identical, and it will be the firmware that does it.In the other thread someone was able to let me know the B and D models use the same eeprom chip, and thos does too:http://ww1.microchip.com/downloads/en/DeviceDoc/21673E.pdfNow, here is where the hackery comes in, and where I need your help. I've never messed with EEPROM before, I hear you can use an arduino to read and write it, unsure if you can dump the rom to a file that way, if not, I need to know what tools to get to do this properly. Is there much risk of bricking it just by swapping ROM's?I also need someone to dump the ROM of their UT71D, so that I can try replacing it, or comparing the ROMS, and hopefully that will unlock the full memory!I look forward to your responses, this should be fun if we get what we need.Here is a picture of the board, the EEPROM chip is under the metal shield on the top right.

author: XOIIO
author_rank: Super Contributor
timestamp: May 08, 2014, 03:18:39 pm
content: Giving this a bump since it was posted at a bad time.

author: Dongulus
author_rank: Regular Contributor
timestamp: May 08, 2014, 03:41:12 pm
content: Does the C model have the same size RAM as the D model? I would check that to make sure that UNI-T didn't knock down the storage size in the C model.Unfortunately, I have the UT71B so I can't help you with getting a hold of the D model ROM contents.

author: mariush
author_rank: Super Contributor
timestamp: May 08, 2014, 05:45:05 pm
content: Let's see... you blew up your previous multimeter, you can barely afforded to buy this other multimeter... and now you want to fuck it up by messing with this new multimeter you have. Does that sound intelligent?How about you cut it out and have a fully working multimeter on your bench for your hobby instead? You don't really NEED 10k points of data logging, I'm almost sure. If you do, you can already just use the cable it comes with instead of risking damage to your only multimeter.

author: XOIIO
author_rank: Super Contributor
timestamp: May 08, 2014, 05:50:01 pm
content: Quote from: mariush on May 08, 2014, 05:45:05 pmHow about you stop acting like a fucking asshole and get out if you have nothing to contribute.

author: mariush
author_rank: Super Contributor
timestamp: May 08, 2014, 06:14:49 pm
content: Fine.. want me to contribute so i will.That microchip IC is just an i2c eeprom.. you can just solder 4 wires (voltage, gnd, and two data wires) and read the eeprom data with arduino. That won't help you much, the eeprom most likely contains the calibration data in the first bytes and the rest of the IC is empty and available for holding data ... assuming 4 bytes per point, you have 40000 bytes used from the 512 kilobits (64000 bytes)The meter has its own microcontroller with its own firmware in the flash (most likely the IC in the top left corner, because it has sticky with C on it which means it was flashed with the C firmware) which reads the calibration data from the eeprom, sends it to the cyrustek meter chip and then just uses uart or i2c or something to talk back and forth with the cyrustek chip.Chances are.. you need jtag or something to even try to talk with the mcu, it will probably have its code/memory protected (90% sure) so you can't READ the binary data in it, and unless you find the IC and a good datasheet, you won't know how to flash it.IF you find a firmware for 71D/E/Whatever you still need to decrypt it, dissasemble it, understand the code and where the 100p restriction is, change those bits in the binary, encrypt it back and then flash your mcu.Sounds easy enough, right?

author: Shock
author_rank: Super Contributor
timestamp: May 08, 2014, 08:56:32 pm
content: Well another point is trying to update a 71C to 71D is kind of silly (but don't let that stop you).They cost $20 difference so hardly worth the bother there.From what I understand it's not just the fuses it's the input protection as well. I know there was some discussion on the 61E had subtle differences on the Euro supplied model is this the same with the 71 series? Being able to safely measure mains power sounds useful to me.An illumination mod would come in handy. That 30 seconds max limit is a bit sad.As I also mentioned in another post the probes that come new with the 71 series seem to have some coating (or at least not cleanable by alcohol) on them. When testing the diode test it's slower to beep touching the sides of the probes but fast touching the probe tip to screw part, I'm wondering if buffing the surface will improve them.

author: XOIIO
author_rank: Super Contributor
timestamp: May 08, 2014, 10:07:17 pm
content: Quote from: Shock on May 08, 2014, 08:56:32 pmThat's something else I was hoping I might be able to change in firmware, the max 30 second timeout is a pain.As for input protection it only has a PTC, I want to add some MOV's, but apparently that will affect capacitance readings, unsure how much by, or if it will affect resistance as well.I got this on sale so with shipping it only cost me around $104, sadly the UT71D was not available or I would have gotten that.It's excellent for it's money, I just wish it had a bit more than 100 internal datalogging points, you'd think it would be at leas 1000, that would make the upgrade to the D more sensible.

author: miguelvp
author_rank: Super Contributor
timestamp: May 10, 2014, 07:27:42 am
content: Did you try to install the PC software? with the usb optocoupler it came with you can just datalog as much as you want (until the battery dies).The PC usb driver just acts like a com port so you probably can roll your own software, but I didn't look into the details.Also check out:http://sigrok.org/it shows the UN-T61 series as supported not the 71 series and I haven't tried it myself but it might work? source is available too so if it doesn't you could add support.

author: XOIIO
author_rank: Super Contributor
timestamp: May 12, 2014, 01:31:58 am
content: Quote from: miguelvp on May 10, 2014, 07:27:42 amYeah the software works great, it would just be nice to have more internal storage.