ANENG AN8001, 6000 count true RMS Multimeter for $14.

[shved]

Has anyone managed to get UART working?
I'm looking for cheap DIY data-logging solution. I've successfully modded several UNI-T and HoldPeak meters before.
My thought process is: PC<USB<USB-UART bridge RX<IR photo transistor<IR LED<cheap meter UART_TX.

[wasedadoc]

The Parkside PDM 300 C1, C2 and C3 DMMs have a serial pin. The protocol has been reverse engineered and there are at least two versions of software written to get readings from it.

It is a basic auto-ranging meter whose CAT rating has been certified by TUV.  Parkside is a Lidl brand and these meters appear in their "special buys" every so often at £10 or local equivalent. ebay.uk currently has several listings from £15 upwards.

Pictures show how I've added a serial to USB board.  The serial output pin is mostly high so to minimise the added power consumption the optocoupler (legs in the air) is between serial pin and the positive output of the regulator.  I used a Sharp PC817 opto and a 1k series resistor was low enough to reliably transmit to its output side.  That's a BC558 (PNP) and 10k resistor piggybacked on the USB-serial module.  I did need to shave the module's PCB slightly to fit it in.  There is a 3mm thick plastic sheet between the DMM PCB and the module.  Epoxy glue securing everything including the opto.

Just connect to computer USB port with normal USB to micro-USB cable.

Photo is of a C1 version.  I also have a C2 version which is identical except that the DMM chip is directly on the main PCB but Tx pin is there and marked.  Info on the internet says the C3 version (Spring 2022) is also amenable.

[floobydust]

Has anyone managed to get UART working?

It's doubtful the Serial TX Data Output pin is actually bonded to the die, like this AN8002 pic apparently shows.
You can look for a substrate diode reading, or scope the pad as another way to see if there are signs of a connection. I did not find one.
EEPROM location 0xFD (stock is 0x82) can be programmed for some options:
"V1.9 Add UART upload option: 24C02 FDH.6=1 select 9721 compatible format, FDH.6=0 (dtm0660L version), FDH.5=1 send 14Bytes, FDH.5=0 send 15Bytes (dtm0660L version)" refers to bit 6 and bit 5.

[shved]

Thanks everybody.
New version(currently sold) is on a different PCB with different chip & pinout.
Best guess on the chip is SD7501 by SDIC Microelectronics ( http://www.sdicmicro.cn/upload/img/2021-08/611cad9c519ad.pdf ).
If anybody has some info - please share.
No EEPROM, no reaction on the extra button pins, no signal on UART pin. Pretty unmodable, as far as I can see. Shame.
Internals photo included.

[shved]

For my data-logging project I've bought and modded VICTOR VC-921 instead of Aneng AN8001.
https://www.eevblog.com/forum/testgear/hacking-the-victor-vc-921/25/