BLETeensy -- BLE for Teensy 4.x + Murata Type 1YN (CYW43439) Copyright (c) 2026 Earle F. Philhower, III. All rights reserved. LGPL licensed, see headers.

This library lets a Teensy 4.x board become a BLE server (i.e. the thing your phone or PC connect to, like a BLE heart rate monitor) or a BLE client (the thing that connects out to remote devices).

It's a port of Earle Philhower's BLE library from arduino-pico -- originally written against the Pico SDK's BTstack integration for the Pico W's onboard CYW43439 -- retargeted to run on top of the BTstackTeensy library instead, which provides the same underlying BlueKitchen BTstack HCI/GAP/GATT stack for a Teensy 4.x + Murata Type 1YN (CYW43439) module. The public BLE/BLEServer/BLEClient/ BLECharacteristic/... API is unchanged from the Pico version; it tries to be relatively compatible with the ESP32 BLE and Arduino.cc ArduinoBLE libraries, but isn't guaranteed to be so.

Requirements

• A Teensy 4.x board (Teensy 4.1 or 4.0) wired to a Murata Type 1YN (CYW43439) module as documented in BTstackTeensy's README -- HCI UART on Serial8 (pins 33-36 by default) plus the BT_ON pin.
• The BTstackTeensy library installed alongside this one (depends=BTstackTeensy in library.properties); this library includes BTstackTeensy's raw BTstack headers (btstack.h, hci.h, gap.h, ble/sm.h, ...) directly rather than going through BTstackTeensy's own BTstackTeensyManager/BTstackTeensy wrapper classes, so both libraries can be installed side by side without any symbol clashes.

Porting note: BLE.update()

On the Pico W, BTstack runs on the second core via the Pico SDK's async_context, so the Arduino sketch's loop() never needs to service it. Teensy 4.x has no such background driver -- BTstackTeensy polls its HCI UART and BTstack's run loop from a function that must be called every iteration of loop() (see BTstackTeensy::loop()). This port adds that same requirement here as BLE.update(): call BLE.update() once per loop() iteration (see the examples) or BLE processing -- including BLE.begin() itself, which blocks until the local address is known -- will stall.

Examples

• Beacon, BLEClientDemo, CharacteristicOnWrite, CustomService, Scan, SerialBLE -- ported from the original Pico examples; button/ID calls specific to the RP2040 (BOOTSEL, pico_get_unique_board_id(), rp2040.getFreeHeap()) were swapped for Teensy-portable equivalents.

bleteensy