Author Topic: EEVblog 121GW Multimeter Issues  (Read 250614 times)

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Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #1150 on: February 10, 2020, 09:11:33 am »
That is interesting and I hadn't seen any glitches in the logs I collected during testing and playing with it initially or with some of the later firmware (generally I don't use the 121GW for that much due to other gear available).

It was an intermittent problem, didn't always show up.
 

Offline mpallewa

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Re: EEVblog 121GW Multimeter Issues
« Reply #1151 on: February 10, 2020, 09:28:42 am »
Diagram attached. The power source is a Li-ion battery with a voltage of approx 3.945 volts.
 

Offline e0ne199

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Re: EEVblog 121GW Multimeter Issues
« Reply #1152 on: February 10, 2020, 02:21:53 pm »
UPDATE:
The SD card logging issue has been resolved, although I have not tested it myself yet, it just came through.
v2.04 is attached.

Quote
ST Micom recommended our team to use their library in order to send every 60 data packet stored in the EEPROM built-in the ST micom to the SD card.  We found this issue is caused by our using this library. We solved this issue by sending every 60 data packet stored in the RAM, instead of the EEPROM, built-in the ST micom to the SD card.

So it seems it was an issue with the ST micro SD card library.
IIRC they used to use their own driver, but then switched to the ST driver a suggested, so maybe this issue wasn't present on some much older version perhaps.

how about bargraph bug in VA mode? is it also solved too?
anyway UEi should take a look at VA mode measurement bugs too because there are lots of people talking about that here
« Last Edit: February 10, 2020, 02:25:38 pm by e0ne199 »
 

Offline dcac

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Re: EEVblog 121GW Multimeter Issues
« Reply #1153 on: February 10, 2020, 05:07:47 pm »
UPDATE:
The SD card logging issue has been resolved, although I have not tested it myself yet, it just came through.
v2.04 is attached.

Quote
ST Micom recommended our team to use their library in order to send every 60 data packet stored in the EEPROM built-in the ST micom to the SD card.  We found this issue is caused by our using this library. We solved this issue by sending every 60 data packet stored in the RAM, instead of the EEPROM, built-in the ST micom to the SD card.

So it seems it was an issue with the ST micro SD card library.
IIRC they used to use their own driver, but then switched to the ST driver a suggested, so maybe this issue wasn't present on some much older version perhaps.


Thanks Dave! I was suspecting the problem was something like that, i.e. based on twp_rules comment about buffering samples in the EEprom:
Quote
The only functionality storing samples in EEPROM (as opposed to RAM) has given the firmware is (seemingly) the ability to play back the last 60 samples of the most recent logging session even after the meter has been restarted. Other than that, it's damaging to the ROM and probably pretty power-hungry. Why did they do it this way?

IMHO twp_rules did an amazing job disassembling the 1.02 FW and I've been using this as an template to disassemble the more recent FW's.

I did try an hack that used RAM buffer instead, it's a good thing the STM32 has allot of unused RAM. But even though this hack seemed to solve the repeating samples issue there was still some stalling every 60 samples when the the buffer gets translated to plain text and stored on the SD card. This stalling could be up to 10-14 sec during longer logging sessions and during this time incoming samples are simply lost. This issue could perhaps be dependent on the type of SD card used, I used the original that came with the meter. I will be interesting to test if V2.04 also have an affect on this.

 
 


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