project: extending HP3478A functionality

[Miti]

Here are the Gerbers, the schematic, and the BOM for this project. Take the BOM with a grain of salt, check before you order.
I've never made this version of board but the changes from the one that I have made are minimal, adding a pull down resistor and changed the USB pin header from 4 to 5 pins.

[Vaionko]

Thank you kirill for this awesome project! Getting continuity with this is actually the reason I got a 3478A, otherwise I would've gotten something else. After a bit of fighting with bad connections, it works! I don't have any equipment to plug into the GPIB port, so I took the whole port out and replaced it with a 3D printed bracked with an Arduino Nano mounted on it and the USB port accessible on the back of the meter. This project is great!

The 3D print file if anyone's interested: https://www.printables.com/model/1403032-arduino-nano-mount-for-hp-3478a-multimeter

Edit: Now that I said this, I actually tested it with the bracket installed, and it doesn't work... I get a serial connection but no response to GPIB commands or the SRQ key... 

[kuwoyuki]

Here's my version on a WCH CH32V203. There's a demo video and a PCB link in the readme.
It's a bit simpler and I didn't implement a 2 button nav with "LOCAL", and just did a hover/timer menu instead since I think it's a bit hacky and couldn't get it to work reliably, maybe kirill_ka can explain how it's done?