Hi there! I'm Joonas, a passionate software developer from Finland.
I'm a senior software dev during the day, hardware researcher and emulator developer in the evening, Game Boy specialist 24/7.

I've worked in the IT industry since 2004, and had my own IT consulting company Jawsy Solutions during 2009-2013.
I've used Java since 2000, Scala since 2007, and Rust since 2014.
I'm currently freelancing as a hands-on software/firmware/hardware/gateware consultant via my own company Merulogic Oy.
I studied at Aalto University and have a B.Sc degree in Bioinformation Technology and a M.Sc degree in Computer Science.

My current interests include:

• Rust
• Game Boy emulators and hardware analysis
• FPGA/CPLD systems (with VHDL)
• Digital electronics

Notable public projects

• Game Boy Hardware Database: Data and photos of various types of Game Boy consoles and game cartridges
• Gekkio/gb-schematics Various Game Boy -related schematics based on reverse engineering work
• Gekkio/gb-research Game Boy hardware research and reverse engineering (including fully traced and RE'd SM83 CPU core)
• Game Boy: Complete Technical Reference: A Game Boy reference manual focused on answering the unanswered questions
• GhidraBoy: Sharp SM83 / Game Boy extension for Ghidra reverse engineering framework
• Gekkio/gb-hardware: Game Boy -related custom hardware
• Mooneye GB: A Game Boy research project and emulator written in Rust

Talks I've given

• October 2022: DIY air quality sensor network with Rust, Nordic nRF, and BLE (at Rust Finland Meetup)
• May 2018: Reverse Engineering fine details of Game Boy hardware [v3.0] (at Reaktor Breakpoint 2018)
• April 2018: Reverse Engineering fine details of Game Boy hardware [v2.0] (at Reaktor Meetup: Hack the hardware)
• January 2018: Reverse Engineering fine details of Game Boy hardware (at Disobey 2018) [errata blog post]
• October 2017: imgui-rs: Immediate mode GUIs with Rust (at Rust Finland Meetup)

Recent blog posts

• 8 years of Game Boy tweets - December 26, 2022
• Power consumption of Game Boy flash cartridges - April 17, 2021
• HHL Bivert Module V2 - technical review - August 22, 2020
• Decapped random chip - STMicro L78M05CV - August 12, 2020
• Decapped random chip - Microchip PIC16LC72A - August 12, 2020