DIY HDMI Switcher Project – The Beginning

This is a relatively long post, so if you don’t feel like reading the whole thing, just scroll to the end and read the TL;DR section.

Yes, I know I haven’t posted in a while. I was on vacation in Vermont last week, during March Break. We went skiing there. I’ve also been working on a little electronics project. I’ve never done anything like it before, until now I’ve been playing around with circuits on breadboards. This is the first electronics project I’ve done that has a practical application.

So what is this challenging and novel project of mine? It’s an HDMI Switcher. It has two HDMI inputs and one HDMI output. This device chooses which HDMI input will be connected to the output.

Here’s a real world example to help visualize it (This is, in fact what I’m going to be using it for); I have a PC and a Blu-Ray player, among other things. I use both of them with my HDTV. But if I want to use my PC on the TV, I have to go behind and pull the HDMI cable out of the blu-ray player and plug it in to my PC. Then if I want to use the blu-ray player again, I have to go behind the equipment again and switch the cable.

What this device will do is make it so that I can have them both plugged in at the same time, but I can press a button to switch between them. So I can choose which one is going to the TV at the touch of a button, without having to switch up any cables whenever I want to use one of them and the other happens to be plugged in.

It isn’t finished. Indeed, it’s still in the planning stage. I have a schematic drawn, but I won’t post it yet because it’s half-finished! I’m making it on a PCB, and prototyping it on a breadboard isn’t an option because we’re dealing with clock signals at frequencies up to ~340MHz. Therefore, controlling parasitics in this circuit is critical. Also, the multiplexer IC I’m using calls for a specific controlled amount of differential transmission line impedance. To be honest, I don’t know what that means. That’s another thing I’ll have to figure out (This is made much easier because the kind people on ##electronics have pointed me in the right direction!). But I know that I can’t create a controlled value of it on a breadboard.

So, I’m going to have to spend lots of time on the planning stage, because if I order parts and get a PCB fabricated, and I made a mistake, that’s money and time down the drain because then I have to order a new PCB and maybe new components too.

So, let’s hope it works! And even if it doesn’t, it will be a great learning experience. This project will involve surface-mount soldering, PCB design and ordering, programming an AVR microcontroller chip, and more. And all of those things I have never done before.

This is the start of a series of posts, which will be complete when the project is complete.

TL;DR:


- I’m making an HDMI Switcher

- It will require designing and ordering a PCB, and soldering surface-mount parts, and programming an AVR microcontroller

- I’ll be posting regularly about it on this blog, I’ll be sharing lots of information that I’ve learned and experiences that I have throughout the project.