Questions

and going a bit off topic from the B450 board...
Do you want to start a new Thread ? Maybe it could be better since it could also benefit other Projects.
I'd like to see some Code on GitHub

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1. esp32-s3 keyboard hid is working with translation for Azerty-BE, no mouse (yet). might look into generalizing it for other layouts such as Nicohoods implementation.
Nice

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Googling a bit implementing the Mouse might be quite straightforward
Arduino core for the ESP32. Contribute to espressif/arduino-esp32 development by creating an account on GitHub.
github.com
2. thinking about it, might be slow over wifi network, manageable over 100Mbit ethernet
I think we have to distinguish 2 kinds of Issues: latency (ping) vs bandwidth (throughput).
In normal Usage we don't need that much Throughput IMHO unless mounting an ISO Image over NFS or something (assuming there are Libraries and the ESP32-S3 has Hardware Resources to accomodate that).
WiFi Latency ... MEH

. It should work "alright" for most Stuff, but moving the Mouse is something I can imagine feel VERY sluggish. Not that we will need it much on a Server IMHO

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you'd have to emulate the mass storage from an ISO, don't know if the esp32-s3 has the headroom for that. mounting an sdcard to the host can be done with an additional board. a very small image can be put inside an ffat or exfat in the flash storage (4MB on my devices, shared with binary of the running program, larger on other devices), for a kind of bootstrapping or something like it could be possible.
That's probably one of the Reasons why I'm still NOT set on the ESP32-S3 and am thinking ... is it worth getting the Radxa Rock 2F/2A for line 12 EUR ... 18 EUR plus ~ 5-8 EUR for the SD Card ?
That way you can fully decouple all of the Systems, have local & decentralized KVM, able to emulate USB Gadgets (you could then mount an ISO from a NFS Fileshare as a USB Gadget, thus exposing the Drive to the HOST System I think).
3. esp32-s3 does HID. Connected to a pc, server, laptop: it gets power from usb port and uses usb port to send keyboard commands
I'd rather Power if from 5VSB, that Way you are ready once you implement ATX Power Control with the ATX Board

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Because I don't think USB keeps being powered ON while the System is Shutdown (but still AC Connected of course).
Without 5VSB you'd be left locked out if you turn the System Off ...
I agree USB Power Supply is fine for e.g. the VGA 2 HDMI Converter, because if the System is OFF, obviously there is no Video.
But you have to make sure you don't get locked out with the Board that is doing the ATX Power Control. Because in my View at least, it would make sense to do that locally. Or do you plan on doing that centralized as well ?
4. kind of, didn't like the extra usb TTL devices, leonardo is overpriced. Esp32-s3 has it builtin usb hid capable. I prefer a compact solution but with possibilities for extensions such as ethernet, display, atx control, and I want to easily customize for the 4x1 VGA selector.
Why would you need extra TTL Devices and/or Arduino Leonardo ? Might as well get a full blown Linux SBC like Radxa Rock 2F/2A/S0 or Radxa Zero 3E/3W at that Price Point.
motivation was realizing an idea i had for quite a while now and possibly cost (excluding time spent of course), mostly : using what I already had lying around.
Fair enough

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a single esp32-s3 (*) can do out of the box
a 5 eur budget does:
- USB HID
- probably also wako over usb if a motherboard doens't have a (working) WoL),
- wifi
Given the Issues with BIOS I'm not sure I would trust either WoL or USB Wake-up to be honest ...
a 10 eur budget also does
- VGA to hdmi
- HDMI capture (excluding a 'old' x86 device gathering dust)
Assuming the VGA Switch and NOT fully indipendent Solution I guess ...
a 15 € eur budget additionally gets
- ethernet 10/100Mbit
- 0.96" display
- atx pwr, rst and led monitoring
Aren't you a bit Optimistic on the ATX PWM, RST and LED Monitoring ?
Assuming 2 EUR for Ethernet and 1 EUR for Display ... 2 EUR for ATX+RST+LED Monitoring seems too cheap to be true.
Considering that the PiKVM Project reccomends IIRC some specific Panasonic Relays. I believe those are quite expensive.
of course these can be mixed/matched.
of course you need an 'other' device for the daemon, nginx, streaming, etc.
... maybe the s3 could do the html serving part too. so you only need a way to bring the video signal to your monitor (hdmi over ethernet or so... ) if you want even lower cost
(*) I got some esp32-s3 shipped for 3.59 € each (be careful not to get the 2MB flash version, that one works too but cumbersome since OTA updates might be difficult).
I think I got the N16R8 for like 6 EUR a year ago or so. Feels like I've been ripped off as usual ...
EDIT 1: although, to be fair about the Mass Storage Emulation (ISO/IMG Mounting), I don't think I EVER did that in the last ~ 5 Years or so (and previously maybe with Supermicro IPMIViewer, when it still worked). I always attached a Physical USB Drive to the System whenever I needed to perform some Rescue Operation. So I don't think it's worth to pay for a dedicated SBC for each System "just" for that Premium
