Author Topic: EEVBlog 121GW Discussion thread  (Read 209256 times)

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Offline fanOfeeDIY

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Re: EEVBlog 121GW Discussion thread
« Reply #75 on: January 21, 2018, 04:38:50 pm »
I just uploaded a video reviewing current measurements of 121GW, Fluke 87-V, Keysight U1241B.

I did not spend much time for rendering, and my camera is not good at auto focusing so
at least I tried to have the voice quality reasonable.

Please enjoy. :)

https://youtu.be/EfV_u2MFOPU
 
 

Online mikeselectricstuff

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Re: EEVBlog 121GW Discussion thread
« Reply #76 on: January 21, 2018, 04:44:39 pm »
Any word on publishing the format of the cal data and firmware files - these would be prerequisites for alternative firmware - probably possible to reverse-engineer, though it would be a bit of a pain.
BTW is a full end-user recalibration possible ( this would make reversing the cal data easier if nothing else)?

So, IDA and I have been having a bit of fun over the past week and I now have a perhaps 80% complete IDA database of the 1.02 firmware. I'm hesitant to release it because a) it's not done and b) I don't know what UEI would think. I also can't test a lot of theories because my own meter is not here yet.

Anyway, regarding the format of the firmware file. The CPU is an STM32L152 family Cortex-M3 ARMv7-M processor. I don't know what exact chip it is. If anyone could send me a photo of the exact chip in the meter, I would be grateful. The EEVBlog.bin file is burned into ROM starting at 0x08006000. It has a standard Cortex-M3 vector table at the start, where the first 32 bits are the initial SP and the second are the reset vector (+ 1 because the processor always operates in Thumb-2 mode). This is enough to get it disassembling correctly in IDA, or to start your own firmware once the exact chip is known.

Regarding calibration data, it actually seems possible to load and save the calibration area of the EEPROM to the SD card. As before, I can't test it cause I don't have a meter. There is a non-zero chance you could lose all your cal data or start a fire.  If you want to try, here is the procedure:
  • Boot holding the MEM key, or maybe boot the meter with no keys and quickly press MEM. (I'm not entirely sure) Screen will show SdCAL if you did it.
  • Press PEAK to load calibration data from SD card (screen shows SdSEt) or REL to save data to card (screen shows SdSAv).
  • Press MODE to do it. If successful, screen shows SAvEd. Else, screen shows -Err-.
  • Turn off the meter. The data is now in cal.bin on the SD card.
The cal.bin file is a copy of the first 1200 bytes of EEPROM. The first 48 bytes are used for settings, the rest of the 1200 bytes is calibration factors, and the rest of the EEPROM is involved with logging.

A lot of the ranges share factors and there are some I'm not too sure about. The official manual is pretty light on details, and it seems there are other things such as a bonus 50Mohm range calibration and some frequency calibration factors for the AC ranges which are not mentioned. (And what's with 10% for the AC ranges? Is that 10% of full scale as opposed to a dead short?) Fortunately, for most modes and ranges, it is indeed a simple 0 offset and a full-scale gain and I know which ones use which factors. Sadly, I'm not a metrologist, and these areas are heavy on algorithms I don't understand, so I'm having trouble. But I intend on communicating whatever I learn when I do learn it.

And Dave, could you give me an OK/over my dead body on releasing the work?
Maybe start a new  hacking thread?
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Offline bicycleguy

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Re: EEVBlog 121GW Discussion thread
« Reply #77 on: January 21, 2018, 06:13:36 pm »
I just uploaded a video...

Surprised you didn't mention the burden voltage on the 121's secondary display.  I see you didn't hook it up in the video, but would have been nice to compare it's value with the other meters.

thanks
« Last Edit: January 21, 2018, 06:16:16 pm by bicycleguy »
 
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Offline Iagash

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Offline ez24

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Re: EEVBlog 121GW Discussion thread
« Reply #79 on: January 21, 2018, 09:06:51 pm »
Maybe start a new  hacking thread?

There is already one: https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-firmware-details/

Thanks 

Now that there is talk of firmware hack, I am starting to get interested because I think someone is going to come up with something to make me want to buy one.  I am sure UEI does not understand this.

YouTube and Website Electronic Resources ------>  https://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Online EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #80 on: January 21, 2018, 10:01:03 pm »
Any word on publishing the format of the cal data and firmware files - these would be prerequisites for alternative firmware - probably possible to reverse-engineer, though it would be a bit of a pain.
BTW is a full end-user recalibration possible ( this would make reversing the cal data easier if nothing else)?

So, IDA and I have been having a bit of fun over the past week and I now have a perhaps 80% complete IDA database of the 1.02 firmware. I'm hesitant to release it because a) it's not done and b) I don't know what UEI would think. I also can't test a lot of theories because my own meter is not here yet.

Anyway, regarding the format of the firmware file. The CPU is an STM32L152 family Cortex-M3 ARMv7-M processor. I don't know what exact chip it is. If anyone could send me a photo of the exact chip in the meter, I would be grateful. The EEVBlog.bin file is burned into ROM starting at 0x08006000. It has a standard Cortex-M3 vector table at the start, where the first 32 bits are the initial SP and the second are the reset vector (+ 1 because the processor always operates in Thumb-2 mode). This is enough to get it disassembling correctly in IDA, or to start your own firmware once the exact chip is known.

Regarding calibration data, it actually seems possible to load and save the calibration area of the EEPROM to the SD card. As before, I can't test it cause I don't have a meter. There is a non-zero chance you could lose all your cal data or start a fire.  If you want to try, here is the procedure:
  • Boot holding the MEM key, or maybe boot the meter with no keys and quickly press MEM. (I'm not entirely sure) Screen will show SdCAL if you did it.
  • Press PEAK to load calibration data from SD card (screen shows SdSEt) or REL to save data to card (screen shows SdSAv).
  • Press MODE to do it. If successful, screen shows SAvEd. Else, screen shows -Err-.
  • Turn off the meter. The data is now in cal.bin on the SD card.
The cal.bin file is a copy of the first 1200 bytes of EEPROM. The first 48 bytes are used for settings, the rest of the 1200 bytes is calibration factors, and the rest of the EEPROM is involved with logging.

A lot of the ranges share factors and there are some I'm not too sure about. The official manual is pretty light on details, and it seems there are other things such as a bonus 50Mohm range calibration and some frequency calibration factors for the AC ranges which are not mentioned. (And what's with 10% for the AC ranges? Is that 10% of full scale as opposed to a dead short?) Fortunately, for most modes and ranges, it is indeed a simple 0 offset and a full-scale gain and I know which ones use which factors. Sadly, I'm not a metrologist, and these areas are heavy on algorithms I don't understand, so I'm having trouble. But I intend on communicating whatever I learn when I do learn it.

And Dave, could you give me an OK/over my dead body on releasing the work?

No problem.
I'm not going to stop hacking, it is encouraged.
And you are right, there is a boot key press mode that saves the CAL data to SD card. v1.01 firmware has a bug in this routine that was fixed in v1.02 (no other changes). Haven't added this to the manual yet.
 
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Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #81 on: January 21, 2018, 10:17:50 pm »
Maybe start a new  hacking thread?

There is already one: https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-firmware-details/

Perhaps it's best to keep that one for official firmware details. And start a new thread dedicated to firmware Hacking.

 

Offline benst

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Re: EEVBlog 121GW Discussion thread
« Reply #82 on: January 22, 2018, 12:21:19 am »
Is there anything known about when (if?) we can expect the iOS app? Looking forward to that!

Thanks,
Ben
I hack for work and pleasure.
 

Offline fanOfeeDIY

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EEVBlog 121GW Discussion thread
« Reply #83 on: January 22, 2018, 03:40:05 am »

Surprised you didn't mention the burden voltage on the 121's secondary display.  I see you didn't hook it up in the video, but would have been nice to compare it's value with the other meters.

thanks

I thought the same, I spent too much time in the first half of explaining USB-UART converter part and wanted to save time with just swapping the meter.
I would like to included it in the future review.
« Last Edit: January 22, 2018, 04:13:43 pm by fanOfeeDIY »
 

Offline MatthewEveritt

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Re: EEVBlog 121GW Discussion thread
« Reply #84 on: January 22, 2018, 04:07:16 pm »
Anyway, regarding the format of the firmware file. The CPU is an STM32L152 family Cortex-M3 ARMv7-M processor. I don't know what exact chip it is. If anyone could send me a photo of the exact chip in the meter, I would be grateful.
See here https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1406994/#msg1406994] [url]https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1406994/#msg1406994[/url]
 

Offline jordanp123

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Re: EEVBlog 121GW Discussion thread
« Reply #85 on: January 22, 2018, 08:23:29 pm »
Any news on the US meters?
 

Offline logictom

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Re: EEVBlog 121GW Discussion thread
« Reply #86 on: January 23, 2018, 12:13:31 am »
I am having trouble using the Bluetooth, I've got the BT icon on the meter, I have detected the meter on my phone, Google Pixel, and connected, now showing in my paired list, but I see nothing in the app.

Actually just got it to show in the app by forgetting the connection in android settings. But now I've closed the app I cannot get it to reappear.

I've tried the alternative app but that always responds Ble device not found.

Is there a particular sequence on must follow to get it to appear in the app?

When it was connected there appears to be an issue with the fonts in the upper left, auto DC
 

Offline ez24

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Re: EEVBlog 121GW Discussion thread
« Reply #87 on: January 23, 2018, 12:21:14 am »
I am having ....

Can I ask a stupid question - how did you get that screen shot ?

thanks
YouTube and Website Electronic Resources ------>  https://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Offline Cliff Matthews

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Re: EEVBlog 121GW Discussion thread
« Reply #88 on: January 23, 2018, 12:41:31 am »
I am having ....

Can I ask a stupid question - how did you get that screen shot ?

thanks
Roger, this should help. *edit (but you'll have to pull the jpg from the phones DCIM folder and copy or send it to a PC - YMMV)
https://www.greenbot.com/article/2825064/android/how-to-take-a-screenshot-on-your-android-phone.html
« Last Edit: January 23, 2018, 12:43:44 am by Cliff Matthews »
 
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Offline MagFlux

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Re: EEVBlog 121GW Discussion thread
« Reply #89 on: January 23, 2018, 06:14:32 am »
The iOS App has been available in Canada for a week. You may need to search the App Store daily as it could be released where you are very soon.
 

Offline Halcyon

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Re: EEVBlog 121GW Discussion thread
« Reply #90 on: January 23, 2018, 06:24:18 am »
Feature request

Could you include an option in the setup to disable the beeper? It's fine for power-on events and continuity testing etc... but it becomes more of an annoyance every time you turn the knob or press a button. I understand the reasoning behind it, but for me, I'd prefer to have the option to turn it off for key presses/mode changes (or at least select a lower volume).

OFF-LOW-MED-HI options would be fantastic.
« Last Edit: January 23, 2018, 06:26:50 am by Halcyon »
 
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Offline mtdoc

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Re: EEVBlog 121GW Discussion thread
« Reply #91 on: January 23, 2018, 06:42:52 am »
Feature request

Could you include an option in the setup to disable the beeper? It's fine for power-on events and continuity testing etc... but it becomes more of an annoyance every time you turn the knob or press a button. I understand the reasoning behind it, but for me, I'd prefer to have the option to turn it off for key presses/mode changes (or at least select a lower volume).

OFF-LOW-MED-HI options would be fantastic.

Yes, please.  My wife just asked how often that was going to be beeping. Never had her ask that with another meter.  When I said I wasn't sure, she went in another room and closed the door. ::)

Add - now she just yelled at me through 2 sets of closed doors "make the beeping stop!  :rant:
« Last Edit: January 23, 2018, 06:53:23 am by mtdoc »
 

Offline IanB

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Re: EEVBlog 121GW Discussion thread
« Reply #92 on: January 23, 2018, 06:50:12 am »
Can probably reprogram the beep with a pair of wire cutters  >:D
I'm not an EE--what am I doing here?
 

Offline mtdoc

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Re: EEVBlog 121GW Discussion thread
« Reply #93 on: January 23, 2018, 06:55:07 am »
Can probably reprogram the beep with a pair of wire cutters  >:D

Yes, I may have to resort to that. Otherwise my wife may reprogram it "up the side of my head"....
 

Offline Halcyon

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Re: EEVBlog 121GW Discussion thread
« Reply #94 on: January 23, 2018, 06:59:20 am »
Can probably reprogram the beep with a pair of wire cutters  >:D

Yes, I may have to resort to that. Otherwise my wife may reprogram it "up the side of my head"....

I just want to clarify, I want the beep on power-up and continuity, just no other time.
 

Offline mtdoc

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Re: EEVBlog 121GW Discussion thread
« Reply #95 on: January 23, 2018, 07:07:09 am »
Can probably reprogram the beep with a pair of wire cutters  >:D

Yes, I may have to resort to that. Otherwise my wife may reprogram it "up the side of my head"....

I just want to clarify, I want the beep on power-up and continuity, just no other time.

Yes, loss of continuity beep would be tragic - so the wire cutters will be held at bay for now.  I could tolerate the power on beep but I really don't want any of the other beeps though.   Volume control would also be good as you say.
 

Online EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #96 on: January 23, 2018, 07:26:02 am »
I have v1.04
Negative VA issue supposed to be fixed (haven't checked)
Beep is now off by default.
Ohms autoranging has been improved down to just under 4.5sec or so. They claim any faster and the meters would require recalibration. I don't know why they can't at least partially use the bargraph ADC for this.
 
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Offline Towger

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Re: EEVBlog 121GW Discussion thread
« Reply #97 on: January 23, 2018, 08:11:19 am »
I have v1.04
I don't know why they can't at least partially use the bargraph ADC for this.

Might be worth while getting David to have a good look at the code.  If it can be 'deciphered', with his strong maths background I am sure the algorithm can be improved/rewritten more.

Or just publish the code...

Is there going to be a solution to the wobbly knobs? [For those who already have a meter. ]
« Last Edit: January 23, 2018, 08:13:39 am by Towger »
 
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Offline hayatepilot

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Re: EEVBlog 121GW Discussion thread
« Reply #98 on: January 23, 2018, 09:34:30 am »
Ohms autoranging has been improved down to just under 4.5sec or so. They claim any faster and the meters would require recalibration. I don't know why they can't at least partially use the bargraph ADC for this.
Great news.  8)
Will it be further reduced for the 2nd batch? Calibration will not be a problem since it would be from the factory.
 

Offline Halcyon

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Re: EEVBlog 121GW Discussion thread
« Reply #99 on: January 23, 2018, 09:53:54 am »
I have v1.04
Negative VA issue supposed to be fixed (haven't checked)
Beep is now off by default.
Ohms autoranging has been improved down to just under 4.5sec or so. They claim any faster and the meters would require recalibration. I don't know why they can't at least partially use the bargraph ADC for this.

Thanks Dave, is there an official support page for the 121GW where we can download vetted firmware and manuals etc... (past and latest versions)? I think a lot of us would be keen on updating as I think most (all?) were shipped with v1.01 to-date?
« Last Edit: January 23, 2018, 09:56:12 am by Halcyon »
 


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