Electronics > Repair
HP 34401a DMM with leaking segments
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qu1ck:
hakko
Thanks for interesting data. I looked at SPI data dump you posted and the control frame headers on new panels differ from the old, no wonder my firmware doesn't work. But I kinda expected that.

For example first thing immediately obvious is that text control frames start with 0xff 0x2d instead of 0x00 0x7f and annunciator update starts with 0xff 0x00 instead of 0x7f 0x00.
Also there seem to be random 0x00 frames from cpu to panel sometimes (button state query?).

If you have time could you compile a table of control frames like found here? https://github.com/openscopeproject/HP34401a-OLED-FW/blob/master/protocol.md
That would help update firmware for these new panels.
qu1ck:
Thanks to coromonadalix who stepped up to help with capturing SPI data on a newer model 34401a meter I was able to figure out the differences in the protocol, which turned out to be minimal.
Here is new firmware that should be compatible with both old and new meters. firmware_debug.bin will spit out received decoded data onto usb serial line. If anyone can validate it I will publish new firmware and the fix to github.
coromonadalix:
had  tons or problems to make a blue pill work,  boot loader problems i did not understood    i'm a total nooob  for this

He sent me an firmware.bin  file who replace the boot loader, and have the debug option,   thus always needing an st-link to work.

Heres the results on a serial monitor (attached photo)  , i dont have an oled display, never received it.

my comments
-----------------------------------------------------------------------------------------------------------------------
Inverted the miso mosi line going to the blue pill    (if im not mistaken)
pb13 is the clk
pb14 is the 34401a mosi line / blue pill miso
pb15 is the 34401a miso line / blue pill mosi
ground wire

Arduino IDE board enumeration is :

BN: Maple Mini
VID: 0x1EAF
PID: 0x0004
SN: Upload any sketch to obtain it

Select com9 ; it says  Maple Mini

I start the Arduino serial monitor and voila   is see the data coming out ...  woh hoooooooo

Q: What are the 2 lines of Annunciators meanings ?
they have 0000  0001   etc ...

----------------------------------------------------------------------------------------
Going right to left in the menus

Dcv - Acv - 2w / 4w ohms - freq - period - DCI - ACI   all went fine, annunciators follow fine,   played with the range arrow more digits less digits    all ok

-----------------------------------------------------------------------------------------------------------------------

problems

Continuity          spits data very fast  and crashes
Diode test         spits data very fast and crashes  the pill red light flashes ?

The rs232 monitoring seems to crash the communications ... not enough buffers ?? or slow down theses tests ??

Have to unplug power or a long reset and restart rs323 monitoring

If i do a long reset the red led flashing is gone, restart monitoring, all is fine, if i'm outside  continuity or diode tests.


Goood   job you have done     thks for your patience and many emails exchanged.
coromonadalix:
Edit    with continuity open   data is going very fast

rs232 monitor   Termite  hold longer  before it crashes too ??

Termite wont reopen the connection   even if the pill is resetted ???
Arduino monitor does ???  after the pill was resetted
wictor:
It would help, if serial printing had lower priority, since it is disturbing spi decoding during debug.
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