Bluetooth GATT Characteristic Reference

CGM Status (0x2AA9)

org.bluetooth.characteristic.cgm_status

The CGM Status allows the Collector to actively request the current status from the CGM Sensor, particularly when the CGM measurement is not running and the status cannot be given in the measurement result in the Status Annunciation.

Quick Summary

Payload length is 7 bytes. This page is generated from official GATT XML and presented as implementation-ready guidance.

At a Glance

Key reference details for BLE implementation, interoperability testing, and AI-assisted troubleshooting.

Property	Value
Name	CGM Status
UUID	0x2AA9
Type	org.bluetooth.characteristic.cgm_status
XML Root	Characteristic
Source File	org.bluetooth.characteristic.cgm_status.xml
Field Count	3

Field Specification

Parsed field definitions from the source XML value structure.

Field	Requirement	Format	Unit	Exponent	Notes
Time Offset	Mandatory	uint16	org.bluetooth.unit.time.minute	0	The Time Offset Field specifies the actual relative time difference to the session start time.
CGM Status	Mandatory	24bit	-	-	The structure of the CGM Status Field shall be identical to the structure of the Status Annunciation Field, as defined in the CGM Measurement Characteristic "Sensor Status Annunciation Field". It always consists of three octets regardless the value.
E2E-CRC	C1	uint16	-	-	If the device supports E2E-safety (E2E-CRC Supported bit is set in CGM Feature), the status is secured by a CRC calculated over all fields.

Byte Layout and Decode

Payload length is 7 bytes.

function decodePayload(dataView, offset = 0) {
  const time_offset = dataView.getUint16(offset + 0, true);
  // Parse cgm_status (24bit) according to Bluetooth format rules.
  const e2e_crc = dataView.getUint16(offset + 2, true);
  return { time_offset, cgm_status, e2e_crc };
}

Use Cases and Integration Notes

BLE Telemetry

Map characteristic values into dashboards and alerts for device observability.

Firmware Regression

Compare decoded fields across builds to detect protocol or scaling changes.

App Integration

Build stable parsing paths that convert raw payloads into typed app models.

Implementation Checklist

Validate payload length and mandatory fields before decode.
Decode with Bluetooth-specified signedness, unit, and exponent handling.
Convert units at presentation boundaries to avoid drift in business logic.
Persist raw packets and decoded values for reproducible troubleshooting.

FAQ

What is CGM Status in Bluetooth GATT?

CGM Status is defined as a Bluetooth GATT characteristic entry with type org.bluetooth.characteristic.cgm_status and UUID 0x2AA9.

What UUID identifies CGM Status?

The UUID for CGM Status is 0x2AA9.

How should I parse CGM Status?