wtb: KVM input PS/2, output VGA, only with manual switches - Page 1
Forum section: electronics / general

author: legacy
author_rank: Super Contributor
timestamp: May 04, 2019, 04:04:57 pm
content: Common KVMs usually offer two way for switching from a computer to another:- they offer special keys to be pressed on the attached keyboard- they offer manual switch buttonsfor the special application I am designing I do not want any special keys on the keyboard: the user MUST only press buttons (and only if he/she is allowed to do so ... now you can guess why I don't want keys)I am not able to find a solution, neither a product made this way ... ideas?

author: legacy
author_rank: Super Contributor
timestamp: May 04, 2019, 04:08:39 pm
content: inputs are:four PS/2 lines for the keyboardfour PS/2 lines for the mouseoutput are:four lines for the VGA, and signals are about 1024x768@60Hzplus the console line:one PS/2 lines for the keyboardone PS/2 lines for the mouseone VGA channelso it's nothing special about spec.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 04, 2019, 04:51:34 pm
content: I've seen KVMs with physical knobs to switch, and since the setting on the knob would be wrong with hotkey switching as well, I presume they don't use that, though you may be hard pressed to find one with a lot of connections (I know of 2 connection and I think 3).Alternatively, if the internal architecture has a micro that monitors the PS/2 lines for the hotkey signal rather than routing them all internally, you may be able to lift a pin/cut a trace and just disable that functionality. If it's a KVM with all the signals routed into an integrated switching chip, then this option probably can't work.

author: legacy
author_rank: Super Contributor
timestamp: May 04, 2019, 04:59:30 pm
content: Quote from: DaJMasta on May 04, 2019, 04:51:34 pmYup, I have just analized a couple of KVMs made by DLINK and the MPU is embedded into a big chip.

author: Ian.M
author_rank: Super Contributor
timestamp: May 04, 2019, 05:13:36 pm
content: If the KVM has indicator LEDs for which device is selected, + manual buttons, you could program a MCU to monitor the LEDs and buttons, and if it switched due to a hotkey rather than a button, immediately switch back to the previous PC.

author: Shock
author_rank: Super Contributor
timestamp: May 05, 2019, 10:11:20 pm
content: I have one from the early 1990s was hideously expensive at the time due to all the gender bender cables. Mines not for sale but you can still buy them.https://sewelldirect.com/vga-ps2-manual-kvm-switch-4https://www.ebay.com/itm/352641805912

author: Brumby
author_rank: Unknown
timestamp: May 06, 2019, 06:06:03 am
content: Quote from: Shock on May 05, 2019, 10:11:20 pmTruly old school - just a mechanical switch.Seems to satisfy the brief.

author: legacy
author_rank: Super Contributor
timestamp: May 07, 2019, 10:33:34 pm
content: for my applicatio, the KVM needs to be digital, controller by a MPU and the switch must be not accessible by the end user. I will probably build one by myself.

author: cowasaki
author_rank: Frequent Contributor
timestamp: June 09, 2019, 07:54:28 am
content: Only issue you may have is that PS2 devices often don't work unless plugged in on switch on. So here you would have, potentially, several machines where it wouldn't work because those machines hadn't seen the PS2 device. You would need your device to appear as a PS2 keyboard to each computer all the time and then take an input from a PS2 keyboard and send that to the relevant computer. It's simple enough with a micro controller and a software serial port for each computer and another for the keyboard.