Electronics > Repair

HP 34401a DMM with leaking segments

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Zucca:
Congrats, well done!

HighVoltage:
How nice to see it on hackaday.
Congratulations.

coromonadalix:
Have you seen this display ?  RS232 interface   would it be possible to adapt / interface it ??? would the physical size fit ???

http://noritake-vfd.com/gu256x64d-7000bx.aspx

pdf
https://www.eevblog.com/forum/repair/fluke-8846a-repair-shenanigans/?action=dlattach;attach=511772

qu1ck:
You can interface it (using parallel, rs232 is too slow) but it's too big. I think you can fit at most 135x35mm display without taking dremel to your dmm.
Also it costs half the dmm :D

justanothername:
So.
I spent the day trying to get the display working, but I must give up for now, I'm completely stuck.
Installing the platformio IDE and the tools in windows was not easy, i must say this seems to be a linux-only project. I really would apreciate just a .hex file to upload with JFLASH but there is nothing on github.
So I don't really know if I did everything right, since there is a tool needed in Windows to get the driver working (Zadig) and there are many driver options to choose from. I was able to flash the bootloader onto the MCU by soldering SWO wires onto it. And I was able to find the correct settings in Zadig to upload it at least once. The status now is that it displays the bargraph, but nothing else (see attached picture).
I was not sure how to connect to the PCB to the display board of the 34401a, but at least clock and int seemed clear. I tried crossing out MISO and MOSI (DI and DO) but no reaction.  The problem now is that i don't know if it just can't decode the display data or if it the MCU somehow crashes after the bargraph is drawn.
So:
What is the correct connection? Is there a hex or bin that works when i just flash it by SWO? how should I set the boot jumper (I can see by looking the picture that position F is soldered)? How can i assure that the program is working at least?
That was quite a frustrating journey until now :)

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