Author Topic: Openterface USB KVM  (Read 2322 times)

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Online NiHaoMikeTopic starter

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Openterface USB KVM
« on: May 12, 2024, 09:20:34 pm »
https://www.crowdsupply.com/techxartisan/openterface-mini-kvm
Basically, it allows you to use an app on your PC to control any device that has HDMI or VGA video out and USB keyboard/mouse support. It could be especially interesting for scopes that don't have a particularly responsive remote interface.
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Offline PlainName

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Re: Openterface USB KVM
« Reply #1 on: June 09, 2024, 02:02:09 pm »
Interesting. Seems to be a modern version of the Lantronix Spider. Plus is that it uses HDMI; minus is it's USB only so you have to be physically connected to the kit. If it had a network option I'd buy one today.
 

Offline Nominal Animal

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Re: Openterface USB KVM
« Reply #2 on: June 09, 2024, 05:55:06 pm »
It's based on the MacroSilicon MS2109 HDMI-to-USB IC, using standard USB Video (UVC1.0) and USB Audio (UAC1.0) protocols over USB 2.0 (max. 480 Mbit/s).  It is commonly used in low-cost USB HDMI video grabbers.

(I cannot get to en.macrosilicon.com right now, but klayers.net has the chips and their datasheets.)

As it uses the standard UVC1.0 and UAC1.0 protocols, Linux and other OSes do not need device-specific drivers.  In Linux, all applications supporting UVC/UAC will Just Work, including OBS Studio.  (The HID interface looks like to be implemented using an USB-TTL converter pair.)

There is an USB 3 variant of the chip, MS2130 (see klayers.net for datasheet and specs), also using UVC1.0 and UAC1.0, just over USB 3, which allows better frame rates.  (Aforementioned OBS Studio should work equally well with these on Linux at least.)

Both MS2109 and MS2130 datasheets contain a Typical Application schematic, and to my eyes ––  purely a hobbyist, not a professional! –– the Openterface v1.6 2024-06-05 schematic is exactly that, just with reasonable power supply circuits and a couple of USB hubs and a USB-TTL+TTL-USB pair implement an USB HID KVM port.

Considering you can get MS2130-based HDMI-to-USB converters from AliExpress (look for MS2130) for under 10€, and MS2109-based HDMI-to-USB converters from Amazon (look for MS2109) for under 10€, I personally would not be happy to pay 10× the price for the Openterface one.  Granted, being open source hardware, and having the hubs and device-side USB ports makes Openterface a complete solution, and for anyone not as poor as myself it probably is worth the price, but for me, it's just not enough bang for the buck.  30-40€ I'd accept, but 100€ is just too much.

Apologies for being the negative-nancy here.  😢
« Last Edit: June 09, 2024, 05:57:34 pm by Nominal Animal »
 
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Online NiHaoMikeTopic starter

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Re: Openterface USB KVM
« Reply #3 on: June 16, 2024, 08:47:03 pm »
The real value is the software that integrates the streaming and keyboard/mouse emulation. I would be interested to try to make a DIY version of the USB bridge device, to be used in combination with a common HDMI capture card. Might be a good idea to wait for the software to become more stable first, to avoid debugging issues only to find it's not the DIY device at fault.
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Offline Nominal Animal

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Re: Openterface USB KVM
« Reply #4 on: June 16, 2024, 11:52:40 pm »
I would be interested to try to make a DIY version of the USB bridge device, to be used in combination with a common HDMI capture card.
Teensy 4.x can do dual USB device: it has two identical (AFAIK) USB 2.0 implementations built-in, both LS/FS/HS capable.  Unfortunately, Teensyduino currently only supports Device on one port and Host on the other, due to time constraints and other things being requested more often.

The second USB port is on pads on 4.0, and on a pin header in 4.1.  4.1 also has an Ethernet interface, and you can add 8Mbytes or 16Mbytes of PSRAM, to make one or both Device sides Ethernet-remotable.  Net security is a pain, though.  ATECC608B might help.

I've been thinking about making a small TI ISOUSB211 or AD ADuM3166/4166 low/full/high-speed isolator for the second port on the Teensy, so one could safely connect it between two computers and have it look like a combined mouse/trackpad/keyboard plus a couple of USB Serial endpoints to both (for data transfers; 200+Mbit/s is easily achieved in practice).  A Dual Device, in other words.  Teensyduino already has such in the Arduino interface; it's just currently limited to the one specific USB device.  I haven't looked carefully, but duplicating the code to ensure the two devices won't interfere with each other, should work.
 

Online SiliconWizard

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Re: Openterface USB KVM
« Reply #5 on: June 17, 2024, 12:26:51 am »
ATECC608B might help.

This is an interesting chip, and it's also not expensive. Note that the full datasheet is only available via a NDA, though.
 


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