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org.bluetooth.characteristic.cgm_measurement

Last Modified: 2014-11-17 Approved: Yes

Name: CGM Measurement

Type: org.bluetooth.characteristic.cgm_measurementDownload / View

Assigned Number: 0x2AA7

Summary:

The CGM Measurement characteristic is a variable length structure containing one or more CGM Measurement records, each comprising a Size field, a Flags Field, a Glucose Concentration field, a Time Offset field, a Sensor Status Annunciation field (optional), a CGM Trend Information Field (optional), a CGM Quality Field (optional), and an E2E-CRC Field (mandatory if this feature is supported).

Value Fields

Names Field Requirement Format Minimum Value Maximum Value Additional Information
Size
Information:
The Size Field represents the size of the CGM Measurement record. In minimum the size is 6 octets and is enlarged by more octets indicated by the Flags Field (Sensor Status Annunciation Field, CGM Trend Information Field and CGM Quality Field) and the E2E-CRC Supported bit in CGM Feature. The Size Field itself is included in the overall length calculation.
Mandatory
uint8 N/A N/A None
Flags
Mandatory
8bit N/A N/A
Bit Field
Bit Size Name
Definition
Key Value Requires
0 1 CGM Trend Information Present
0 False
1 True C1
1 1 CGM Quality Present
0 False
1 True C2
5 1 Sensor Status Annunciation Field, Warning-Octet present
0 False
1 True C4
6 1 Sensor Status Annunciation Field, Cal/Temp-Octet present
0 False
1 True C4
7 1 Sensor Status Annunciation Field, Status-Octet present
0 False
1 True C4
2 3 Reserved for future use
CGM Glucose Concentration
Information:
The CGM Glucose Concetration Field contains the CGM glucose concentration in mg/dL as a SFLOAT data type. The SFLOAT-Type is a 16-bit word comprising a signed 4-bit integer exponent followed by a signed 12-bit Mantissa, each in twos-complement form.
Unit:
org.bluetooth.unit.mass_density.milligram_per_decilitre
Exponent: Decimal, 0
Mandatory
SFLOAT N/A N/A None
Time Offset
Information:
The following values are defined for the Time Offset Field, specifying the relative time difference of the single CGM values to the session start time. Value: (0x0000 - 0xFFFF), Description: (Time offset in minutes as offset to the Session Start Time).
Unit:
org.bluetooth.unit.time.minute
Exponent: Decimal, 0
Mandatory
uint16 N/A N/A None
Sensor Status Annunciation
Information:
The Sensor Status Annunciation Field is an optional field comprising up to three octets. It is only attached if one or more bits are set to “1”. Only the affected octet(s) shall be added and indicated by the Flags Field. The Sensor Status Annunciation Field shall be attached to every CGM Measurement Record to which the status applies.
C4
variable N/A N/A
Bit Field
Bit Size Name
Definition
Key Value
0 1 Session Stopped
0 False
1 True
1 1 Device Battery Low
0 False
1 True
2 1 Sensor type incorrect for device
0 False
1 True
3 1 Sensor malfunction
0 False
1 True
4 1 Device Specific Alert
0 False
1 True
5 1 General device fault has occurred in the sensor
0 False
1 True
8 1 Time synchronization between sensor and collector required
0 False
1 True
9 1 Calibration not allowed
0 False
1 True
10 1 Calibration recommended
0 False
1 True
11 1 Calibration required
0 False
1 True
12 1 Sensor Temperature too high for valid test/result at time of measurement
0 False
1 True
13 1 Sensor temperature too low for valid test/result at time of measurement
0 False
1 True
16 1 Sensor result lower than the Patient Low level
0 False
1 True
17 1 Sensor result higher than the Patient High level
0 False
1 True
18 1 Sensor result lower than the Hypo level
0 False
1 True
19 1 Sensor result higher than the Hyper level
0 False
1 True
20 1 Sensor Rate of Decrease exceeded
0 False
1 True
21 1 Sensor Rate of Increase exceeded
0 False
1 True
22 1 Sensor result lower than the device can process
0 False
1 True
23 1 Sensor result higher than the device can process
0 False
1 True
6 2 Reserved for future use
14 2 Reserved for future use
CGM Trend Information
Information:
The CGM Trend Information Field contains the CGM Trend information in (mg/dL)/min as an SFLOAT data type. This field is optional if the device supports CGM Trend information (Bit 15 in CGM Feature is set to 1) otherwise excluded.
Unit:
org.bluetooth.unit.mass_density.milligram_per_decilitre
Exponent: Decimal, 0
C1
SFLOAT N/A N/A None
CGM Quality
Information:
This field contains the CGM Quality information in % as an SFLOAT data type. The SFLOAT-Type is a 16-bit word comprising a signed 4-bit integer exponent followed by a signed 12-bit Mantissa, each in twos-complement form. This field is optional if the device supports CGM Quality (Bit 16 in CGM Feature is set to 1) otherwise excluded.
Unit:
org.bluetooth.unit.percentage
Exponent: Decimal, 0
C2
SFLOAT N/A N/A None
E2E-CRC
Information:
If the device supports E2E-safety (E2E-CRC Supported bit is set in CGM Feature), the measurement is secured by a CRC calculated over all fields. The computation of the CRC is done using a CRC-CCITT generator polynomial g(D)=D16+D12+D5+1 (i.e.210041 in octal representation) with a seed of 0xFFFF. This field is mandatory if the device supports E2E-CRC (Bit 12 in CGM Feature is set to 1) otherwise excluded.
C3
uint16 N/A N/A None

Note:

The fields in the above table are in the order of LSO to MSO. Where LSO = Least Significant Octet and MSO = Most Significant Octet

C1: Optional if device supports CGM Trend Information (Bit 15 is set in CGM Feature) otherwise excluded.

C2: Optional if device supports CGM Quality (Bit 16 is set in CGM Feature) otherwise excluded.

C3: Mandatory if device supports E2E-CRC (Bit 12 is set in CGM Feature) otherwise excluded.

C4: Optional if bit 5 or bit 6 or bit 7 of the flgas field is set to “1”, otherwise excluded.