Diving Deep Into The Game Boy LCD Protocol

[Craig] wanted to make the original Game Boy LCD screen do his bidding so he sniffed out the data protocol that it uses. We were amused when he mentions that there’s an army of people out there looking to build pointless crap as part of a hobby. Guilty. And he goes on to outline why this LCD screen is a great resource for hobbiests.

As you can see in the pinout above, it uses 5V logic, with a 4 MHz data clock. These traits are both very friendly to a wide range if inexpensive microcontrollers. If you know how to address the display it should be very easy to use. Furthermore, the low pin count is thanks the to a 4-shade grayscale screen, limiting the data pins to just two. [Craig] hooked up his Saleae Logic probe to capture communications and walks us through what he discovered. During this process he proved to himself that he had figured out the protocol by exporting captured data from the logic probe and reassembling it into an image on his computer.

Tools: Saleae Logic, Logic Analyzer

A logic analyzer records bus communications between two chips. If you’ve ever had a problem getting two chips to talk, or wanted to reverse engineer a protocol, a logic analyzer is the tool you need to spy on the bus.

The Logic is a USB logic analyzer with eight channels and sampling rates up to 24MHz. Among hobby-level logic analyzers, the Logic has a good mix of features and decent sampling rates. We’ve been following Joe Garrison’s work on the Logic for a long time. If you’ve ever considered bringing a product to market, you can learn a lot from Joe’s blog that documents his development process.

When it debuted, the Logic was so popular that it was hard to buy one. It’s now widely available, and Saleae gave us one to try. Read our review below.

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