CGM Status (0x2AA9): byte layout
GATT characteristic · org.bluetooth.characteristic.cgm_status · read from the Bluetooth SIG’s repository on 2026-10-17 · commit 408f4a0 (2026-10-14)
CGM Status is Bluetooth GATT characteristic 0x2AA9, org.bluetooth.characteristic.cgm_status in the Bluetooth SIG's assigned numbers. The SIG's GATT Specification Supplement file lays its value out as 3 fields: Time Offset, CGM Status and E2E-CRC.
- UUID
- 0x2AA9
- Identifier
org.bluetooth.characteristic.cgm_status- The SIG’s description
- The CGM Status characteristic is used to represent the current status of a continuous glucose monitor (CGM) sensor.The structure of this characteristic is defined below.
- Service the SIG’s files tie it to
- None: no file in the repository lists this characteristic under a service.
- Source file
- gss/org.bluetooth.characteristic.cgm_status.yaml
Byte layout: 3 fields
In the order the SIG’s structure lists them. Type and size are as published; sizes count octets except where a struct is marked as sized in bits. The offset is printed only where every earlier field has a fixed size; where an earlier field can be absent or vary, the cell names what it depends on. “Present when” is read from the field’s own “Present if” line, shown in full in the field notes below.
| Offset | Field | Type | Size | Present when | Unit |
|---|---|---|---|---|---|
| 0 | Time Offset | uint16 | 2 | Always (fixed size) | — |
| 2 | CGM Status | boolean[24] | 3 | Always (fixed size) | — |
| 5 | E2E-CRC | uint16 | 0 or 2 | Present if E2E-CRC Supported bit in CGM Feature characteristic is set to 1 | — |
Field notes
Each field’s text in the SIG’s file, line by line.
- Time Offset uint16 · 2
- The Time Offset field specifies the time since the Session Start Time (see CGM Session Start Time (0x2AAA)).
- CGM Status boolean[24] · 3
- The structure of this field is identical to the structure of the combined Status fields as defined in Sensor Status Annunciation in CGM Measurement, but it always consists of three octets regardless of the value.
- E2E-CRC uint16 · 0 or 2
- CRC calculated over all fields except the E2E-CRC field itself. See
§ crc_calculationfor details.Present if E2E-CRC Supported bit in CGM Feature characteristic is set to 1
Guides on this site
No guide on this site names 0x2AA9 yet. The connected-devices guides cover pairing, subscribing and testing for the device types they do name.
Questions
- What is the UUID of the CGM Status characteristic?
- 0x2AA9. The Bluetooth SIG's characteristic_uuids.yaml lists CGM Status as 0x2AA9 with the identifier org.bluetooth.characteristic.cgm_status. No file in the SIG's repository ties it to a service: the repository lists service and characteristic UUIDs separately.
- Which CGM Status fields are optional?
- 1 of its 3 fields has a published size that can be zero: E2E-CRC (0 or 2; Present if E2E-CRC Supported bit in CGM Feature characteristic is set to 1). Time Offset (2) and CGM Status (3) have a fixed size.
- In what order does the CGM Status structure list its fields?
- 1. Time Offset (uint16, 2, offset 0); 2. CGM Status (boolean[24], 3, offset 2); 3. E2E-CRC (uint16, 0 or 2, offset 5). Sizes are as the SIG publishes them; an offset is given only where every earlier size is a plain number.
Source
Read on 2026-10-17 from gss/org.bluetooth.characteristic.cgm_status.yaml and assigned_numbers/uuids/characteristic_uuids.yaml in the Bluetooth SIG’s public repository (branch main, commit 408f4a0, committed 2026-10-14), by scripts/fetch-bluetooth-gatt.mjs. The file’s notice says it is proprietary to Bluetooth SIG, that furnishing it grants no licence, and that it is subject to change without notice; it is © Bluetooth SIG, Inc., and its text is quoted here for identification. Generated by AIFitnessAPI, which is not affiliated with Bluetooth SIG; the SIG’s file remains the authority. The full notice and the conventions used on these pages are on the reference hub.