Bluetooth Smart-based wearable sensors provide wireless 360° freedom of movement on ‘active virtual reality’ gaming platform
Nordic’s multiprotocol nRF51822 SoC enables Virtuix Omni platform to simultaneously support Bluetooth Smart and proprietary 2.4GHz wireless connectivity while addressing latency challenge
Nordic Semiconductor today announces that Austin, Texas-based Virtuix has selected Nordic’s multiple award-winning nRF51822 multiprotocol System-on-Chip (SoC) for its new Virtuix Omni virtual reality (VR) motion gaming platform. The nRF51822 SoC provides wireless connectivity between up to 16 wearable sensor modules and a sensor hub, as well as to Bluetooth® Smart Ready smartphones, tablets, or personal computers.
The omnidirectional motion platform allows for ‘active virtual reality’ in which a player uses their whole body to control their actions―running, walking, sitting and “strafing”―with 360° freedom of movement.
The base of the platform is a smooth, concave disc, allowing the user to walk, run, and change direction freely when wearing a pair of Virtuix Omni shoes with a proprietary low friction shoe sole. After each stride the user’s feet slide back to the center of the concave platform allowing the action to be repeated to simulate walking or running in the game. The user is also strapped into a lower body harness to keep them centered above the unit while still retaining complete freedom of movement.
The movement of the user’s feet is captured by Virtuix Omni Tracking Pod wireless sensors mounted to the top of the Omni shoes. The Omni Pods are Inertial Measurement Unit (IMU)-based tracking devices employing the Nordic SoC, accelerometer, gyroscope, and magnetometer to accurately track the movement of each foot in any direction, even when jumping.
In its maximal configuration Omni uses 18 nRF51822 SoCs. Up to 16 wearable sensor modules, each powered by an nRF51822 SoC communicate wirelessly with the unit’s sensor hub. Because each nRF51822 SoC is able to connect on up to 8 channels, the sensor hub’s SoCs communicate with eight wearable sensors each. From there the data is transferred to a wireless headset and to a host application running on a Bluetooth Smart Ready device or via USB cable to a PC.
Nordic’s nRF51822 is a powerful and flexible multiprotocol SoC ideally suited for Bluetooth Smart and 2.4GHz ultra low-power wireless applications. The nRF51822 is built around a 32-bit ARM® Cortex™ M0 CPU with 256kB/128kB flash and 32kB/16kB RAM. The embedded 2.4GHz transceiver is fully compliant with Bluetooth v4.2, the latest Bluetooth Smart specification.
A key advantage of the nRF51822 SoC is its multiprotocol capability that enables the Virtuix Omni to simultaneously support both proprietary 2.4GHz and Bluetooth Smart wireless connectivity. The product uses a proprietary 2.4GHz protocol based on Nordic’s Gazell software to communicate between sensors and hub while the hub communicates with the mobile device-powered host application using the Bluetooth Smart or Bluetooth Classic protocol.
The nRF51822 SoC’s high level of integration allowed Virtuix to reduce the size of the PCB and the powerful ARM processor allowed the company to preprocess raw sensor data before wireless transfer, compressing the data stream from the sensor to the hub, boosting effective bandwidth.
“Low latency was our main challenge. In a man/machine system like a VR motion sensor, the system’s latency needs to be low enough that it isn’t perceptible to an average human user,” says David Allan, President of Virtuix. “In our case, we figured our system needed to react in 150 milliseconds or less.
“Bluetooth Smart had the low power we needed, but it didn’t support the latency requirement. So we designed our own 2.4GHz protocol based on Nordic’s Gazell software with low latency yet with a power consumption comparable to Bluetooth Smart.
“Working with Nordic has been great. We got excellent advice on customizing the Gazell protocol for our purposes. And when our board was ready, Nordic’s lab tuned the antenna circuit for us, boosting the signal strength and allowing us to reduce power consumption while holding transmission range constant.”
“The gaming market is undergoing a transformation thanks to VR technology,” says Geir Langeland, Director of Sales & Marketing, Nordic Semiconductor. “Virtuix has employed Nordic’s wireless technology to make its VR gaming experience stand out by taking full advantage of the multiprotocol capability of the nRF51822 SoC. The result is rapid response during gaming combined with the interoperability of Bluetooth Smart for seamless connectivity with smartphones, tablets and PCs.”