RSC Measurement (0x2A53): byte layout
GATT characteristic · org.bluetooth.characteristic.rsc_measurement · read from the Bluetooth SIG’s repository on 2026-10-17 · commit 408f4a0 (2026-10-14)
RSC Measurement is Bluetooth GATT characteristic 0x2A53, org.bluetooth.characteristic.rsc_measurement in the Bluetooth SIG's assigned numbers. The SIG's GATT Specification Supplement file lays its value out as 5 fields: Flags, Instantaneous Speed, Instantaneous Cadence, Instantaneous Stride Length and Total Distance. The first, Flags, is a boolean[8]; 2 of the others are present only when a bit of it is set as the field's text states, so after the first of those, a field's offset depends on which bits are set.
- UUID
- 0x2A53
- Identifier
org.bluetooth.characteristic.rsc_measurement- The SIG’s description
- The RSC Measurement characteristic is used to represent data related to a running speed and cadence (RSC) measurement.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.rsc_measurement.yaml
Byte layout: 5 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 | Flags | boolean[8] | 1 | Always (fixed size) | — |
| 1 | Instantaneous Speed | uint16 | 2 | Always (fixed size) | velocity (metres per second)org.bluetooth.unit.velocity.metres_per_second |
| 3 | Instantaneous Cadence | uint8 | 1 | Always (fixed size) | — |
| 4 | Instantaneous Stride Length | uint16 | 0 or 2 | Bit 0 of Flags is 1 | length (metre)org.bluetooth.unit.length.metre |
| Depends on Flags (bit 0) | Total Distance | uint32 | 0 or 4 | Bit 1 of Flags is 1 | length (metre)org.bluetooth.unit.length.metre |
Field notes
Each field’s text in the SIG’s file, line by line.
- Flags boolean[8] · 1
- See Flags
- Instantaneous Speed uint16 · 2
- Base Unit: org.bluetooth.unit.velocity.metres_per_secondRepresented values: M = 1, d = 0, b = -8Unit is 1/256th of a m/s
- Instantaneous Cadence uint8 · 1
- Unit is 1/min
- Instantaneous Stride Length uint16 · 0 or 2
- Base Unit: org.bluetooth.unit.length.metreRepresented values: M = 1, d = -2, b = 0Unit is CentimeterPresent if bit 0 of Flags field is set to 1
- Total Distance uint32 · 0 or 4
- Base Unit: org.bluetooth.unit.length.metreRepresented values: M = 1, d = -1, b = 0Unit is 1/10 mPresent if bit 1 of Flags field is set to 1
Flags and value tables
The definitions the SIG’s file gives for its fields, every row as published. On a flags table the last column lists the fields whose “Present if” line names that bit.
Flags
The bits of this field are defined below.
| Bit | Description | Fields its condition names |
|---|---|---|
| 0 | Instantaneous Stride Length Present | Instantaneous Stride Length when 1 |
| 1 | Total Distance Present | Total Distance when 1 |
| 2 | Walking or Running Status:0 = Walking1 = Running | — |
| 3–7 | Reserved for Future Use | — |
Guides on this site
The metric RSC Measurement carries, on every platform this site covers — each type quoted in its platform's own words:
The connected-device guides that name 0x2A53:
Questions
- What is the UUID of the RSC Measurement characteristic?
- 0x2A53. The Bluetooth SIG's characteristic_uuids.yaml lists RSC Measurement as 0x2A53 with the identifier org.bluetooth.characteristic.rsc_measurement. No file in the SIG's repository ties it to a service: the repository lists service and characteristic UUIDs separately.
- Which RSC Measurement fields are optional?
- 2 of its 5 fields have a published size that can be zero: Instantaneous Stride Length (0 or 2; Present if bit 0 of Flags field is set to 1); Total Distance (0 or 4; Present if bit 1 of Flags field is set to 1). Flags (1), Instantaneous Speed (2) and Instantaneous Cadence (1) have a fixed size.
- What units does RSC Measurement use?
- The SIG's text names a unit for 3 of the 5 fields: Instantaneous Speed: velocity (metres per second) (org.bluetooth.unit.velocity.metres_per_second); Instantaneous Stride Length: length (metre) (org.bluetooth.unit.length.metre); Total Distance: length (metre) (org.bluetooth.unit.length.metre).
- What do the bits of the RSC Measurement Flags field mean?
- The SIG defines them as: bit 0, Instantaneous Stride Length Present (Instantaneous Stride Length when 1); bit 1, Total Distance Present (Total Distance when 1); bit 2, Walking or Running Status: 0 = Walking; 1 = Running. The remaining bits are reserved for future use.
Source
Read on 2026-10-17 from gss/org.bluetooth.characteristic.rsc_measurement.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.