At last, after a loooong pause, I've resumed my project of replacing my HP34970's front panel PCB, since the VFD was broken **and** I managed to kill the 80C51 controlling the front panel. The new PCB looks decent, it even fit the enclosure! Soon (hopefully) a new blog post on https://whatever.sdfa3.org/tag/34970a.html

So far so good (but I fried an STM32F303 because I fried the MCP1811 LDO, because I swapped the silk screen **marking** of 2 resistors... You know, the ones that set the feedback voltage for the TPS56043 18v->5v converter...) Oh well. Now I need to get back to the laptop to get a working firmware...

Making progress... https://peertube.social/videos/watch/cc6f4327-703f-42f6-8157-03cd0a987387

Still have a few problems to fix:
- selected (dimm) characters are not yet fully supported,
- power off of the front panel not yet implemented
- display is too flickery in some situations , need to investigate how to properly use DMA for the SPI transfert to the display module,
- the code a kind of a mess, but meh

Some progress
https://peertube.social/videos/watch/172bf449-eba7-4429-8840-ab9b2d5398f8

I'd say it's almost good enough, still have a few bits to improve and fix, but it should be good enough soon. Remaining stuff to do:
- implement dimmed icons/flags
- it seems I still sometimes send a keycode to the main unit while it has started a communication (and it does not like this at all),
- I'd the + and - font chars to be more similar

Things I will not do any time soon:
- add USB support; because of https://forums.mbed.com/t/usbdevice-support-for-stm32f3/10685 (I should probably have chosen an STM32F1, which has better support in MBed)