Bluetooth: Continuous Glucose Monitoring Service

The Continuous Glucose Monitoring Service sample demonstrates how to implement the Continuous Glucose Monitoring Service profile using nRF Connect SDK Bare Metal option.

Requirements

The sample supports the following development kits:

Simple board variantsMCUboot board variants

The following board variants do not have DFU capabilities:

S115:

Hardware platform	PCA	Board target
nRF54L15 DK	PCA10156	bm_nrf54l15dk/nrf54l15/cpuapp/s115_softdevice
nRF54L15 DK (emulating nRF54L10)	PCA10156	bm_nrf54l15dk/nrf54l10/cpuapp/s115_softdevice
nRF54L15 DK (emulating nRF54L05)	PCA10156	bm_nrf54l15dk/nrf54l05/cpuapp/s115_softdevice
nRF54LM20 DK	PCA10184	bm_nrf54lm20dk/nrf54lm20a/cpuapp/s115_softdevice
nRF54LS05 DK	PCA10214	bm_nrf54ls05dk/nrf54ls05b/cpuapp/s115_softdevice
nRF54LS05 DK (emulating nRF54LS05A)	PCA10214	bm_nrf54ls05dk/nrf54ls05a/cpuapp/s115_softdevice
nRF54LV10 DK	PCA10188	bm_nrf54lv10dk/nrf54lv10a/cpuapp/s115_softdevice

S145:

Hardware platform	PCA	Board target
nRF54L15 DK	PCA10156	bm_nrf54l15dk/nrf54l15/cpuapp/s145_softdevice
nRF54L15 DK (emulating nRF54L10)	PCA10156	bm_nrf54l15dk/nrf54l10/cpuapp/s145_softdevice
nRF54L15 DK (emulating nRF54L05)	PCA10156	bm_nrf54l15dk/nrf54l05/cpuapp/s145_softdevice
nRF54LM20 DK	PCA10184	bm_nrf54lm20dk/nrf54lm20a/cpuapp/s145_softdevice
nRF54LS05 DK	PCA10214	bm_nrf54ls05dk/nrf54ls05b/cpuapp/s145_softdevice
nRF54LS05 DK (emulating nRF54LS05A)	PCA10214	bm_nrf54ls05dk/nrf54ls05a/cpuapp/s145_softdevice
nRF54LV10 DK	PCA10188	bm_nrf54lv10dk/nrf54lv10a/cpuapp/s145_softdevice

Overview

The Continuous Glucose Monitoring Service (CGMS) is a service that exposes glucose and other data from a personal Continuous Glucose Monitoring sensor.

Allow list

By default, the sample does not use allow-list advertising, which means that any nearby device can connect and bond with the device. Bonded devices are stored in internal non-volatile memory (NVM) and are remembered across power cycles.

You can enable allow-list advertising by setting the CONFIG_BLE_ADV_USE_ALLOW_LIST Kconfig option to y in the base Kconfig fragment (prj.conf). When enabled, only previously bonded devices are allowed to reconnect, which allows faster reconnection and prevents unknown devices from connecting.

When allow-list advertising is enabled and you want to add a new bonded device, existing bonds must first be deleted. This can be done through user interaction, as described in the user interface section.

User interface

Button 0:

When pairing with authentication, press this button to confirm the passkey shown in the COM listener and complete pairing with the other device. See Testing.

Button 1:

Keep the button pressed while resetting the board to delete bonding information for all peers stored on the device.

When pairing with authentication, press this button to reject the passkey shown in the COM listener to prevent pairing with the other device.

Button 2:

Decrease the simulated glucose concentration.

Button 3:

Increase the simulated glucose concentration.

LED 0:

Lit when the device is initialized.

LED 1:

Lit when a device is connected.

Security

The sample integrates Bluetooth: Peer Manager (backed by Bare Metal Zephyr Memory Storage (BM_ZMS) for persistent storage) to support pairing and bonding.

The following security parameters are configured:

Peer Manager security parameters

Parameter	Value	Effect
Bonding	True	Supports storing of pairing information (bonding data).
MITM protection	False	Man-in-the-middle protection not required.
LE Secure Connections	True	Supports LESC pairing.
I/O capabilities	Display and Yes/No entry	Determines local I/O capability, actual pairing method depends on negotiation with peer.

This sample configures the following services and their characteristics with these specific operation modes and required security levels:

Service	Characteristic	Operation	Required security	Effect
Continuous Glucose Monitoring Service	CGM Measurement	Notify	Encryption, no authentication	Connection must be encrypted to subscribe to and receive periodic glucose measurement notifications.
	Feature	Read	Encryption, no authentication	Connection must be encrypted to read which optional CGM features the sensor supports.
	Status	Read	Encryption, no authentication	Connection must be encrypted to read the time offset and sensor status.
	Session Start Time	Read/Write	Encryption, no authentication	Connection must be encrypted to read or set the timestamp that marks when the monitoring session started.
	Session Run Time	Read	Encryption, no authentication	Connection must be encrypted to read the expected run time of the CGM session.
	Record Access Control Point	Write/Indicate	Encryption, no authentication	Connection must be encrypted to retrieve, filter, or delete stored glucose measurement records.
	Specific Ops Control Point	Write/Indicate	Encryption, no authentication	Connection must be encrypted to start or stop a monitoring session and configure settings such as the communication interval.
Device Information Service	All characteristics	Read	Encryption, no authentication	Connection must be encrypted to read device information such as the manufacturer name and firmware version.
Battery Service	Battery Level	Read/Notify	Open, no security	Any connected device can read the battery level and subscribe to battery level notifications.

See Testing for the pairing and bonding steps.

Building and running

This sample can be found under samples/bluetooth/ble_cgms/ in the Bare Metal folder structure.

For details on how to create, configure, and program a sample, see Getting Started with the samples.

Testing

1. Compile and program the application.

2. Connect the device to the computer.

3. Connect to the kit with a terminal emulator (for example, the Serial Terminal app). Note that the kit has two UARTs, where only one will output the log.

4. Reset the kit.

5. In the Serial Terminal, observe that the BLE CGMS sample initialized message is printed.

6. Observe that the Advertising as nRF_BM_CGMS message is printed. You can configure this name using the CONFIG_SAMPLE_BLE_DEVICE_NAME Kconfig option. For information on how to do this, see Configuring Kconfig.

7. Connect to your device using the nRF Toolbox mobile application with the Continuous Glucose service. If the device is not advertising, reset the board with the Reset Board option in Visual Studio Code or by pressing the reset button on the development kit.

8. Your mobile phone should now attempt to pair with your device to encrypt the link. When prompted, check that the passkeys are the same before confirming by pressing Button 0 on the kit and confirming on the mobile phone.

9. Observe that the text Connected and CGMS Start Session is printed in the COM listener.

10. Observe that you receive the CGMS records in the mobile application. The default time between each record is one minute.