Day 22 (published 23 December 2020)

Start Looping

You have made it through this massive version of an “Advent Calendar”, and no matter if you ate all the chocolates in one or two days, or if it took you two months to get through it, you have decided to start Looping.   This “Calendar” will continue to be updated by the Loop and Learn volunteers as information changes, so please come back and visit the relevant sections as time goes on and you have questions.

If you have decided against monitoring the various Facebook, Telegram, Zulip groups on a weekly basis, please at least sign up for the Loop and Learn newsletter so we can blast you an email if we see something that we think is critical you should know about.   If you aren’t interested in hearing about presentations, uncheck the presentations box.  You can always find out about presentations on this site or the FaceBook group  Or you watch them on the Loop and Learn YouTube channel (and subscribe for notices of new videos) after the live event is over.

Below is a checklist that you should carefully go through as you build and start Looping.    Make sure to pay particular attention to the “Cautions” and “Future tasks” sections that come after the checklist, to be successful – you must not skip them.

  • Check that your Mac OS is the most current patch level of whichever OS you are running, you need to be running Catalina or newer to be successful.
  • Check that your iPhone or iPod Touch has at least the version needed to run the branch/fork you want to use.  Note that some branches other than Master Branch require at least iOS 13.
  • Check that you have a compatible pump.   If you are on OmniPod, that is the Eros pods, with the clear plastic tab.   If you have the Dash pods, with the blue plastic tab, they will not work with Loop.    If you have another pump, such as a Medtronic, pay close attention to the info about your pump, including country and version codes, before you try to start looping.
  • You should already have your RileyLink, OrangeLink, or EmaLink in hand.
    • Charge the RileyLink for three hours and unplug it before trying to pair the first time.
    • They sometimes will not pair with a pump if plugged into power.
    • If you are going to Loop with Omnipod, your RileyLink should have a bump with an antenna sticking out the top, if you are going to Loop with another pump, it should not have that bump (this is due to frequency differences).
  • Download or update Xcode (set up command-line tools, add Apple Dev account), Homebrew, Carthage.
  • Make sure your Apple Developer program subscription is valid and visit the site to make sure no new terms or conditions are pending acceptance.
  • Although not absolutely necessary, set up your data storage destination (such as Nightscout).  If you need help with Settings, posting NightScout charts is going to get the fastest advice.  If you need to bring data to your doctor, find out what they use in the office (NightScout, TidePool, something else)?
  • You cannot call in and get replacements for some types of pod failures when Looping (because you won’t have the PDM error code needed).   Consider trying to get your doctor to prescribe more pods than you expect you need.  Many insurances will cover a pod replacement every 2 days.
  • If this is for a child, consider how you are going to handle interactions with the school nurse and when/if/what do you need to add to the 504 plan.   Make sure you are in a position to keep the school from taking away the RileyLink or Phone from your child.
  • Commit to checking in with the “source of truth” for the branch of Loop that you are installing at least weekly to look for safety-related warnings.    If you are not going to check in weekly, at a bare minimum, sign up for the Loop and Learn “general” newsletter, and read it when it shows up in your inbox.
  • Your settings are wrong.    I don’t care how much testing you did, your settings are wrong.   Start with open-loop most of the time, keep checking your settings until you have them close.
    • Don’t be afraid to switch between closed-loop and open-loop often as you get them sorted out.
    • Overnights are often the first part of the day that people close Loop on because with proper settings, it will mute, or prevent low blood sugars.   But, jump in the pool slowly.
    • You can use Loop as simply a PDM to manually enter bolus amounts.   Don’t think it is a race to be full-time looping.
    • And, always, if you have a dodgy CGM, open loop until the CGM is stable again, or changed.   Loop is only as good as the data that is feeding it, if the CGM is giving bad data, do not leave Loop closed and trying to make math decisions based on what you already know is bad data.
  • Download the version you are wanting to run.
    • It is generally recommended that you start with “Master” until you are comfortable with your settings, but
    • You can also use AB or FreeAPS and set it to run exactly like Master, then turn on one auto/micro bolus algorithm at a time as you get things tuned in.
    • Download the latest version of what you decide to run.   Don’t use one you downloaded a few months ago, always go with the latest download.
  • Plug the phone in, take a deep breath, then click on the build button.
  • It may take a long time, but Xcode always ends with Build Succeeded and then copies to app to your phone or Build Failed.  (If you are updating Loop, do not worry – your current app on your phone will not be corrupted if the Build Fails because Xcode will not copy anything to your phone until you get Build Succeeded.)
  • If you run into build problems, be sure to follow the “how to ask for build help” post to get the fastest response.
  • Post a message in Loop and Learn announcing that you have started, or if you are shy, send us feedback.


Test and re-test all your settings.     They are wrong.   Deal with it and fix them.   Settings that work when you do the math a few times a day are going to be much more forgiving than settings that are re-worked for dose decisions using differential calculus looking at trends over the last 30-90 minutes and plotting data points every five minutes looking six hours in the future.

No, your DIA is NOT 3 hours, it is 6. (maybe it is 5.5, but that is an advanced topic), it is NOT 3 hours.    DO NOT use WALSH.   At an absolute minimum, unless you are injecting insulin directly into your bloodstream, your DIA is at least 5 hours.   (Injecting insulin directly into your bloodstream is for a future topic).

Future Tasks

Data for Doctor:   Make a plan for how you will share your data with your doctors!

Updates!  Make sure your Profile expiration date is on your calendar along with your Developer renewal date and your quarterly rebuild.


Please let us know with a post in Loop and Learn that you followed this calendar and made it into Looping.  OR, if you don’t want to post in public, use the feedback form on this page to let us know.

We are all volunteers. We’d like to know if our hard work and passion putting together this information has helped people, or not.

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