I finally decided I might as well make an overall block diagram of the Gameslab system. I was working on changing the design schematics and realized I forgot a couple things. So, I made this block diagram to use as a checklist–makes sure I don’t forget pieces. It also helped to figure out which peripherals would connect to the Zynq PS versus the PL. For example, the LCD touch controller was originally connected to PS I2C pins, but the PL has to be enabled to use the LCD anyway. So, it made more sense to route the touch screen I2C bus through the EMIO.
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While working on the DDR3 interface of the re-imagined Gameslab, I wanted to do some simple sanity checks for signal integrity. Since I don’t really want to pay >$1000 for two PCBs with controlled impedance and a custom stackup, I just wanted to verify my cheap boards from PCB-POOL would work at all. PCB POOL lists the stackup for 6-layer boards on their site, so I plugged these specs into a trace impedance calculator. My best option so far looks like routing the high-speed DDR traces on the inner layers with a reference ground plane above each signal layer. I calculated the impedance at ~63 Ω. Since DDR3 has 34 Ω driver and typically 40 Ω transmission lines, I wanted to at least do a sanity check simulation.
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I bought one of the PSP LCD screens from Sparkfun forever ago, planning on building some kind of game console-like device with it. Slowly, I accumulated more hopeful parts, like the PSP-style thumb-sticks and a touchscreen that fits the LCD perfectly. All these parts are screaming at me to build something cool, so I’m going to build an FPGA based, hand-held game console. From scratch.
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Before I write much about my Gameslab project, I think it’s worth looking back at my Gamesphere project from over four years ago. I still receive a handful of emails per month asking for schematics or help on building a new game console. Usually, these emails are desperate college seniors looking for an easy senior project. And, I’m afraid for the people that are legitimately looking for schematics to learn from, I didn’t make any. That’s part of why I want to look back on my previous project; I want to see what I can do better this time around, and also, what I did well the first time.
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