Bluetooth Low Energy virtual drumkit allows drummers to practice anywhere by creating authentic sounds from sensor-tracked stick movements

Freedrum, drumstick

‘Freedrum’ employs Nordic’s nRF52832 SoC to run angle-tracking algorithms and wirelessly connect drumstick-attached devices to an app where users follow live drumming patterns

Nordic Semiconductor today announces that Freedrum, a Sweden-based startup, has selected Nordic’s nRF52832 Bluetooth® Low Energy (Bluetooth LE) System-on-Chip (SoC) to provide the wireless connectivity for its ‘Freedrum’ virtual drumkit.

In the optimal set-up, Freedrum comprises four compact (80 by 22 by 9mm) and lightweight (16g) wireless devices fitted to the pair of drumsticks and the user’s feet, connected to an iOS-, macOS-, and Android-based partner app using Bluetooth LE wireless connectivity provided by the Nordic SoC.

Built-in gyroscopes and accelerometers track the direction and angle of the drumsticks’- and the drummer’s feet-movement then detect ‘impacts’ that translate to actual drum sounds. Freedrum then transmits the data via MIDI over Bluetooth LE to a paired Bluetooth 4.0 (and later) smartphone or tablet, allowing the user to play their virtual drumkit anywhere and listen live to the generated audio. Musical Instrument Digital Interface (MIDI) is a technical standard that describes a protocol, digital interface and connectors, and allows a wide variety of electronic musical instruments, computers, and other related devices to connect and communicate with one another.

The nRF52832 SoC’s powerful 64MHz, 32-bit Arm® Cortex® M4F processor (combined with large capacity 512kB Flash memory and 64kB RAM) has ample power to cope with the complex Floating Point (FP) computations necessary to run Freedrum’s detailed angle-tracking algorithms at high speed, manage its raw sensor values, and supervise the Bluetooth LE RF protocol software. The data is then relayed via low latency Bluetooth LE wireless connectivity to the user’s smartphone, where the drummer can use the Freedrum app to listen to the beats and view the positions and directions of drumsticks in relation to the virtual drum zones they are hovering over or striking.
We also appreciate the unique level of customer and development support offered by Nordic’s DevZone
August Bering, Freedrum
The Freedrum app features six ‘hit areas’—snare, floor tom, ride cymbal, high tom, crash, and hi-hat—while the user can also open the hi-hat with their left foot and operate the bass with their right foot. Each device employs a 200 mAh LiPo battery that lasts approximately two weeks between recharge when played for one hour per day, thanks in part to the nRF52832’s ultra low power consumption.
Nordic’s unique software architecture provides clear separation between Nordic’s S132 SoftDevice (RF protocol software) and Freedrum’s application code, easing product development. The S132 SoftDevice is a Bluetooth 5-certifed RF software protocol stack for building advanced Bluetooth LE applications. It features Central, Peripheral, Broadcaster and Observer Bluetooth LE roles, supports up to twenty connections, and enables concurrent role operation.
Nordic’s nRF52832 multiprotocol SoC combines the Arm Cortex M4F processor with a 2.4GHz multiprotocol radio (supporting Bluetooth 5, ANT™, and proprietary 2.4GHz RF protocol software) featuring -96-dB RX sensitivity, with 512kB Flash memory and 64kB RAM. The nRF52832 SoC supports over-the-air device firmware updates (OTA-DFU) enabling in-the-field firmware enhancements
“The fast CPU, large memory capacity, and quality of Nordic’s Software Development Kits [SDKs] and documented example code during the development and testing process were all major factors in Freedrum’s decision to select the Nordic SoC,” says August Bering, Founder/Inventor of Freedrum. “We also appreciate the unique level of customer and development support offered by Nordic’s DevZone.”