To address some of the challenges of daily life with diabetes, and because #WeAreNotWaiting, several people worked to figure out how to connect up existing FDA-approved medical devices such as the Dexcom G4 CGM and the Medtronic Minimed insulin pump, using commodity computer / mobile phone hardware and open-source software, to create a complete closed loop Artificial Pancreas System (APS).  The first public example of this was the #DIYPS closed loop system, created in their spare time by @DanaMLewis and @ScottLeibrand in the fall of 2013 based on their earlier work to build the #DIYPS remote monitoring and decision assist system. # DIYPS used the Nightscout project’s uploader to get Dexcom CGM data off the device. # DIYPS was able to become a closed loop with the help of open-source decoding-carelink project created by @Ben West to communicate with Medtronic insulin pumps, retrieve data and issue insulin-dosing commands to pumps that support it. # DIYPS was the base system that led to #OpenAPS. 

In light of the success of #DIYPS closed loop and other simple APS systems built by individuals, Dana and Scott decided to further apply the #WeAreNotWaiting ethos to APS research, believing safe and effective APS technology can be made available more quickly and to more people, rather than just waiting for current APS efforts to complete clinical trials and be FDA-approved and commercialized through traditional processes. 

As a result, #OpenAPS is an open reference design for, and a reference implementation of, a self-built closed loop APS system that uses the CGM sensors’ estimate of blood glucose (BG) to automatically adjust basal insulin levels, in order to keep BG levels inside a safe range overnight and between meals. 

Over the years, there have been hundreds of individuals worldwide who have self-built their own OpenAPS systems, and dozens of people who have contributed to the further development, helping make OpenAPS what it is today!