As far as I know, Tim Nolan started the Arduino-based MPPT solar charge controller design in 2009:

Unfortunately, his web site is down

http://www.timnolan.com/

but the content can still be seen at

http://web.archive.org/web/20140626064134/http://www.timnolan.com/index.php?page=arduino-ppt-solar-charger

In 2013, Julian Ilett created a circuit that uses only one n-channel MOSFET instead of three, using opto-isolators to transfer the PWM signal from the Arduino to the MOSFET.

I tried this approach but didn't like the frequency response of the opto-isolators:

Already at 15kHz, the rectangle pulse is degraded significantly, so I opted for the driver-based half-bridge solution (currently running at 80 kHz).

There are lots more of Arduino-based MPPT's but these are the ones that I have used in my project.