---
title: "Bluetooth"
canonical_url: https://developer.repebble.com/pebbleos/docs/subsystems/bluetooth/
last_updated: 2026-10-21
sdk_version: 4.33.1
---
# Bluetooth

Source: https://developer.repebble.com/pebbleos/docs/subsystems/bluetooth/

`subsys/bluetooth/` is the Bluetooth Low Energy stack interface. Its public API is `include/pbl/bluetooth/`, enabled by `CONFIG_BT`; the [API reference](../apidoc/d3/ddb/group__bluetooth.html) lists every module.

## Layering

`fw/comm/ble/` is the host-side BLE layer and carries substantial design prose:

- `gap_le_connect.c` — connection management and the “connection intent” abstraction that virtualizes the link across multiple clients.

- `gap_le_advert.c` — round-robin scheduling of multiple advertising jobs onto a controller that only holds one payload at a time (the comment predates the current controllers, but the scheduler it describes is still in use).

- `gap_le_connect_params.c` — a primer on connection intervals, slave latency and supervision timeouts, and why the firmware deviates from the spec-recommended parameter-update pause for iOS.

```
flowchart TD
  ble["Host BLE layer<br/>fw/comm/ble/"]
  glue["subsys/bluetooth/"]
  nimble["NimBLE host<br/>third_party/nimble"]
  nrf["NimBLE controller<br/>nRF52 radio"]
  sifli["SiFli LCPU<br/>IPC, SF32LB52"]
  fake["Fake controller<br/>QEMU"]
  uart["H4 controller<br/>CONFIG_BT_HCI_UART"]
  ble --> glue --> nimble
  nimble -- HCI --> nrf
  nimble -- HCI --> sifli
  nimble -- HCI --> fake
  nimble -- HCI --> uart

  classDef app fill:#fa4a36,stroke:#fa4a36,color:#ffffff
  classDef system fill:#fd8a7c,stroke:#fd8a7c,color:#171717
  classDef base fill:#525252,stroke:#525252,color:#ffffff
  class ble app
  class glue,nimble system
  class nrf,sifli,fake,uart base
```

Beneath it sits NimBLE (`third_party/nimble`), glued in by `subsys/bluetooth/`. The HCI transport is chosen per SoC (`BT_HCI`): the NimBLE controller on the nRF52 radio, the SiFli LCPU over IPC on SF32LB52, and a fake controller on QEMU that acknowledges every command so the host runs without a radio. On QEMU the phone link is the emulator’s serial channel, `fw/comm/qemu/`.

## Modules

The [API reference](../apidoc/d3/ddb/group__bluetooth.html) documents every Bluetooth module.

Generated from PebbleOS [3a7b71785](https://github.com/coredevices/pebbleos/commit/3a7b71785fd439666c4a8bc116f561140e8dec01). This page is maintained in the pebbleos repository: [docs/subsystems/bluetooth.md](https://github.com/coredevices/pebbleos/blob/3a7b71785fd439666c4a8bc116f561140e8dec01/docs/subsystems/bluetooth.md).