KVM - PS/2 dongles, USB hub

Projects / KVM Switch  Original post date:04/28/2017

This project is a bit different than my usual one as it utilizes a lot of the off the shelf consumer electronic products as building blocks.  I just don't have the same level access to the parts

I ordered the additional parts for this project.

The keyboard dongle finally arrived today. It took exactly 4 months! They must have the big warehouse like the end of the first Indiana Jones movie. For all that expensive rent in the Canada Custom in Vancouver that handles imports, they could simply hire more people.

Here is what's inside the dongle

It is minimalist design with the black epoxy encapsulated chip, a decoupling cap and the connectors. The good part is that the PS/2 interface supports hot plugging for both mouse and keyboard. It supports scroll mouse.  They really should solder in the shield tabs for the USB connector to provide extra mechanical support.

I have been procrastinating on this trying to figure out a clean way of connecting to the dongle. I could simply drill a hole and solder wire to the dongle, but in the long run it will be a maintenance nightmare.

I start off with using a pencil to mark off the cut out area.

It turns out that I need to cut quite a bit bigger hole. The plastic was easy to work with and reasonably strong which is surprising for cheap Chinese stuff.

I am using a 3 pin fan connector to connect the Clk, Gnd and Data for the keyboard PS/2 signals. This goes to the microcontroller that sense a hotkey sequence and drives the HDMI select button.

The connector is supported on the back side by a small piece of protoboard.

I used a scrap piece of connector pin as mechanical support and connect to the unused footprint for the power LED. The PCB and this pin helps to keep the connector in place.

I made 2 connections on the top side of the PCB. The white wire is connected to Data while the brown one to ground.

The Clk line is connected to green wire at the back.

This is how it looks when glued back together. The connector pins are protected by the case. A dummy connector can be used as a protection cap against short circuiting.