--- title: "AccelerometerService" canonical_url: https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService/ last_updated: 2026-10-28 sdk_version: 4.33.1 --- # AccelerometerService Source: https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService/ Using the Pebble accelerometer The AccelerometerService enables the Pebble accelerometer to detect taps, perform measures at a given frequency, and transmit samples in batches to save CPU time and processing. For available code samples, see the [feature-accel-discs](https://github.com/pebble-examples/feature-accel-discs/) example app. ## Function Documentation int accel\_service\_peek([AccelData](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#AccelData) \* data) Peek at the last recorded reading. ##### Note Cannot be used when subscribed to accelerometer data events. #### Parameters data (out) a pointer to a pre-allocated [AccelData](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#AccelData) item #### Returns -1 if the accel is not running -2 if subscribed to accelerometer events. int accel\_service\_set\_sampling\_rate([AccelSamplingRate](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#AccelSamplingRate) rate) Change the accelerometer sampling rate. #### Parameters rate The sampling rate in Hz (10Hz, 25Hz, 50Hz, and 100Hz possible) int accel\_service\_set\_samples\_per\_update([uint32\_t](https://developer.repebble.com/docs/c/Standard_C.md#uint32_t) num\_samples) Change the number of samples buffered between each accelerometer data event. #### Parameters num\_samples the number of samples to buffer, between 0 and 25. void accel\_data\_service\_subscribe([uint32\_t](https://developer.repebble.com/docs/c/Standard_C.md#uint32_t) samples\_per\_update, [AccelDataHandler](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#AccelDataHandler) handler) Subscribe to the accelerometer data event service. Once subscribed, the handler gets called every time there are new accelerometer samples available. ##### Note Cannot use [accel\_service\_peek()](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#accel_service_peek) when subscribed to accelerometer data events. #### Parameters handler A callback to be executed on accelerometer data events samples\_per\_update the number of samples to buffer, between 0 and 25. void accel\_data\_service\_unsubscribe(void) Unsubscribe from the accelerometer data event service. Once unsubscribed, the previously registered handler will no longer be called. void accel\_tap\_service\_subscribe([AccelTapHandler](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#AccelTapHandler) handler) Subscribe to the accelerometer tap event service. Once subscribed, the handler gets called on every tap event emitted by the accelerometer. #### Parameters handler A callback to be executed on tap event void accel\_tap\_service\_unsubscribe(void) Unsubscribe from the accelerometer tap event service. Once unsubscribed, the previously registered handler will no longer be called. void accel\_raw\_data\_service\_subscribe([uint32\_t](https://developer.repebble.com/docs/c/Standard_C.md#uint32_t) samples\_per\_update, [AccelRawDataHandler](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#AccelRawDataHandler) handler) Subscribe to the accelerometer raw data event service. Once subscribed, the handler gets called every time there are new accelerometer samples available. ##### Note Cannot use [accel\_service\_peek()](https://developer.repebble.com/docs/c/Foundation/Event_Service/AccelerometerService.md#accel_service_peek) when subscribed to accelerometer data events. #### Parameters handler A callback to be executed on accelerometer data events samples\_per\_update the number of samples to buffer, between 0 and 25. ## Data Structure Documentation struct AccelData A single accelerometer sample for all three axes including timestamp and vibration rumble status. #### Data Fields int16\_t x acceleration along the x axis int16\_t y acceleration along the y axis int16\_t z acceleration along the z axis bool did\_vibrate true if the watch vibrated when this sample was collected uint64\_t timestamp timestamp, in milliseconds struct AccelRawData A single accelerometer sample for all three axes. #### Data Fields int16\_t x acceleration along the x axis int16\_t y acceleration along the y axis int16\_t z acceleration along the z axis ## Enum Documentation enum AccelAxisType Enumerated values defining the three accelerometer axes. #### Enumerators ACCEL\_AXIS\_X Accelerometer's X axis. The positive direction along the X axis goes toward the right of the watch. ACCEL\_AXIS\_Y Accelerometer's Y axis. The positive direction along the Y axis goes toward the top of the watch. ACCEL\_AXIS\_Z Accelerometer's Z axis. The positive direction along the Z axis goes vertically out of the watchface. enum AccelSamplingRate Valid accelerometer sampling rates, in Hz. #### Enumerators ACCEL\_SAMPLING\_10HZ 10 HZ sampling rate ACCEL\_SAMPLING\_25HZ 25 HZ sampling rate [Default] ACCEL\_SAMPLING\_50HZ 50 HZ sampling rate ACCEL\_SAMPLING\_100HZ 100 HZ sampling rate ## Typedef Documentation typedef void(\* AccelDataHandler)(AccelData \*data, uint32\_t num\_samples) Callback type for accelerometer data events. #### Parameters data Pointer to the collected accelerometer samples. num\_samples the number of samples stored in data. typedef void(\* AccelRawDataHandler)(AccelRawData \*data, uint32\_t num\_samples, uint64\_t timestamp) Callback type for accelerometer raw data events. #### Parameters data Pointer to the collected accelerometer samples. num\_samples the number of samples stored in data. timestamp the timestamp, in ms, of the first sample. typedef void(\* AccelTapHandler)(AccelAxisType axis, int32\_t direction) Callback type for accelerometer tap events. #### Parameters axis the axis on which a tap was registered (x, y, or z) direction the direction (-1 or +1) of the tap