DIY HDMI Switcher Project – PCBs are Expensive

So, about a month ago I posted about that HDMI switcher project (I really have to post more often… Luckily I have some new, good ideas for posts). I was researching PCB design for high-frequency systems like this, and I’m afraid the news isn’t good.

The PCB would need to carry high-speed differential signals (HDMI). This makes PCB design very critical. The differential impedance has to be controlled to a certain level, which from what I gather is accomplished by carefully controlling the length, width and spacing of the PCB traces that carry these signals while taking into account the material being used. Also, a 4-layer PCB is necessary for low EMI (Electromagnetic Interference) operation. You need these four layers:

- The ground plane
- The power plane
- Low frequency control signals
- High frequency differential signals

But here’s the problem; 4-layer PCBs are very expensive. The cost is in the hundreds. I think it would probably be worth it just for the experience. But I have zero experience designing PCBs, especially PCBs that have to be designed so precisely and with so many layers. I also don’t even know if the circuit will even work at all. So, it might be worth the money if I had any guarantee that it would work. But I can say with almost certainty that it will NOT work the first try, and that’s hundreds of dollars down the drain. I can’t afford that.

So I am sad to say it doesn’t look like I’m going to go ahead with this project any time in the near future. I either need a lot more money to waste, or a lot more experience and knowledge to reduce the risk of costly failures.

I’ll post the (unfinished) schematics and other stuff later, as they might be useful to someone. I’ll definitely have another project soon, that will be a bit less ambitious and expensive. But I can guarantee that it will be a learning experience for me, and it’ll make for some interesting blog posts.