The RileyLink (RL) is an open-source hardware device that can bridge Bluetooth Low Energy (BLE) to 916MHz or 433MHz wireless communication. What does that mean to you? It means RL is the communication highway between your insulin pump, CGM, and iPhone.

Loop will not work without the RileyLink.

Buying or Building RL

The RL is available as a set of PCB files and software, with instructions on how to build your own RL hardware module. All this can be found here: RileyLink Github

If you aren’t up to the task of building your own RL (and most of us aren’t), community members coordinate periodic production runs of RLs. You can place an order here: RileyLink order site

Assembling RL

Your RL will come with the battery disconnected and the parts not already inside the case. It will be up to you to put the RL in the case and attach the battery.

Make sure the lipo battery is well-plugged into the connection. Line up the little ridge appropriately, and push fairly firmly to get the connection tight. Poor battery cable connection can make the Loop communications fail. See photos below, for example.

Common new user errors

The most common two errors for new RL owners are (1) not fully pushing in the lipo battery cable connection and (2) failing to charge the RL. Compare your lipo battery cable with the photos; it takes a bit of oomph to push that plug fully in like the photos show below. Remember to charge your RL each night.

RL with loose battery cable.

RL with properly secured battery cable.

Finally, the board and the battery fit into the slim case fairly tightly as well. Click on the image below to watch a helpful assembly video.

Radio communications

The RL communicates with the pump through radio frequency communications. Numerous factors can influence how well those communications can function...interferences from other devices, temperature, physical blocking, etc.

When your RL and pump first pair together, Loop performs a series of tests that you won't see...they are tuning tests. Basically, RL sends little test messages to the pump and waits for a response. The RL tries this same "ping" to the pump a range of various radio frequencies. The range of radio frequencies it tries is based on the pump you've told RL to expect (Omnipod, Medtronic NA/CA, or Medtronic WW). RL will then record the radio frequencies that provided the strongest response and use that frequency for future pump communications.

Usually this best frequency is pretty constant for any given pump+RL, but during temperature changes it may be that the best frequency is not the one currently set. In the event that RL has problems communicating with the pump, Loop has code built-in that will automatically tell the RL "Hey, try that tuning pump thing again...maybe there's a better frequency we need to try." This retuning is started automatically if pump communications fail for 14 minutes (in other words, two looping cycles).

Bluetooth communications

RL communicates with your iPhone and Loop app through Bluetooth (BT). If your iPhone has BT issues, your Loop will have failures. There have been reports of BT audio devices (such as BT pairings in your car or home audio BT speakers) interfering with the Loop. If you are finding Loop failures frequently happening at a particular location, you may try to troubleshoot if there are BT problems in the area.

Your BT signal strength can be seen in the Loop settings, under the RL menu, on the Signal Strength line. As you move closer and further away from your phone, you can watch that number dynamically change. This line is not displaying the signal strength of your pump communications discussed above.


RL has several lights that you may notice from time to time. There is no 'power' light. If you suspect that your RL is not being powered, try turning it off and on using the small sliding switch. You should see lights in the middle of the board flash when you do this. If they flash, that means the board has power.

A solid blue light that consistenly remains lit on the board could mean one of two things:

If your blue light remains on despite trying a restart, it is time to pull out your backup RL.


The battery that comes with RL is not likely charged completely when it is shipped, so feel free to charge it up. You'll need a mini-USB cable and 0.5A USB charging power supply like your iPhone power supply. RL takes about 2 hours to fully charge (the red light will turn off when fully charged, read note above about red light patterns) and should easily last at least a full day of constant Loop use. Typically, it can go into the 30-hour range without problem. Most people charge their RL each night when they are sleeping. You don't have to worry about leaving the RL plugged in "too long" for charging. It will automatically stop charging the battery when it is fully charged.

Since the best practice is to charge your RL overnight while you sleep, and the battery lasts safely over 24 hours, there is no battery level indicator for the RL. The RL's charge level is not viewable on Nightscout, nor within the Loop app. If you forget to charge your RL overnight, you can recharge it with a portable USB battery in a pinch. A short mini-USB cable could be a good addition to a small gear bag.


The range that your RL will function is heavily dependent on the environment that you are in. Most people wear the RL in a pocket or carry a belt holster during the day. The radio frequency communications will have a shorter range than the BT communications, therefore RL will do better closer to the pump rather than the iPhone if you are deciding on options for carrying gear.

Problematic environments will be places like technical conferences, sports arenas, and other places where wireless communications are heavy and plenty.

Lipo Battery

If you ordered your RL kit, you will need to plug in the battery cable. Please make sure your RL’s battery cable is securely pushed all the way into the socket. Poor battery cable connection can make the Loop communications fail.

RL with loose battery cable.

RL with properly secured battery cable.

Keep your RL and lipo battery protected from damage. Lipo batteries are unsafe when damaged or punctured, so the case is an important part of safe Looping. If your battery is damaged in some way, please disconnect it immediately, and dispose of it (they should be recycled). You can order new batteries on the GetRileyLink website

Removing Lipo Battery

To remove the lipo battery from the RL, please do so slowly and patiently. Work the battery connection side to side slowly to loosen it from the plug. Some people have reported success using small, curved needle nose pliers such as hemostats. Others have used small flathead screwdrivers as shown in this video.

Waiting for RL

Yes, waiting for RL to arrive is extremely difficult if they are backorder. PLEASE be patient, since Loop CANNOT work without RL.

If you're really dying to do something while RL ships, consider these things below.

FIRST AND FOREMOST: If you switched pumps in order to Loop, get used to the pump and start using it before Loop. Sometimes switching pumps will lead to a change in your settings (basals, boluses, etc) simply by the way the new cannula delivers insulin. It's a great idea to use your pump and sets before you ever begin Loop so that you can have one less variable when you do start looping. At least you can check if you need to adjust basals or other settings. The same tips apply for Dexcom. If you are new to Dexcom, start using it before Loop. Get familiar with things like compression lows, sensor variability, and calibration timing before Loop use.

But, if you're familiar with your pump and Dexcom, here are some ideas:

  1. Program your pump with your basal patterns
  2. Enter the other pump settings required for Loop to work
  3. Update your iPhone/iPod touch's iOS, if needed
  4. Update your computer's macOS, if needed
  5. Update your Apple Watch's watchOS, if needed
  6. Download Xcode from the Apple App Store on your Apple computer (this takes more time than you'd expect, it is a large download)
  7. Sign up for a Developer Account. Confirm your enrollment by checking your email afterwards.
  8. Install Homebrew on your computer
  9. Download Loop source code and get started with Loop building
  10. Make customizations, if desired
  11. Build Loop app onto your iPhone/iPod touch
  12. Set up a Nightscout site or update your existing site (optional)
  13. Bookmark the LoopDocs page for future reference
  14. Join Zulipchat and/or the Looped Facebook Group

BUT, then you must wait. You can't go any further with Loop operations until you get the RL. However, if you do all those things above while you will be ready to go as soon as the postman knocks on your door with the delivery.