I am a student at the University of Illinois in Urbana-Champaign who has been tasked with a Senior Design Project that relies heavily on the communication between a Raspberry Pi and GERTboard. The objective of my team's project is to design and implement an herbicide spraying system and mechanical weeding system that can be paired with an autonomous lawn mower (http://www.coolhunting.com/tech/tango-e5-autonomous-mower.php). The lawn mowing robot that was given to us to use as the project platform is compatible with the Raspberry Pi. As our project began to come together, we realized we needed the GERTboard expansion pack to be successful. (Much thanks to Drew Fustini for kindly donating a GERTboard to my Senior Design Team!)
The system is comprised of a tank of herbicide that gets pressurized by an air compressor. The herbicide tank is connected to a solenoid valve that is controlled by a servo. We already had the Raspberry Pi working, but the Gertboard was necessary in providing the system with relays to control the solenoid valve, air compressor and servo.