Yamaha Corp showcased a stick-like device, "Muro Sensor," that can be used to play music by sensing the direction and speed of acceleration.
The Muro Sensor was displayed as a reference exhibit at Wireless Japan 2008. Yamaha plans to use the device in the company's new project, "Music and Health," for its music training classes.
The Muro Sensor, in its about 15cm long chassis, is equipped with a triaxial acceleration sensor, a proprietary 2.4GHz wireless module developed by Nordic Semiconductor ASA of Norway, and so forth. And it looks like Nintendo's "Wii Stick" (Wii Remote).
When a user swings the Muro Sensor, the values of the acceleration are wirelessly transmitted to the base unit of the wireless system and, then, to the user's PC. If the PC is connected to a sound generator, preset sounds can be played based on those values.
Yamaha explained the reason why it used Nordic's proprietary wireless specifications as follows.
"It enables to connect up to 24 units of the Muro Sensor to one base unit at the same time," said Katsumi Matsui, who belongs to the Center for Advanced Sound Technologies, Innovative Technology Division, Yamaha Corp. "Also, its transmission delay is less than 3ms."
The company tried other wireless specifications such as Bluetooth and ZigBee. But the wireless network provided by the main unit of Bluetooth, "Master," can handle only seven terminal devices (called "Slaves") at the same time. And the transmission delay of ZigBee is too long, the company said.
"Humans are sensitive to erratic rhythms," Matsui said. "So, they feel uncomfortable if the lag is as long as 5ms."
Each unit of the Muro Sensor has its own ID and can generate different sounds.
"Suppose, for instance, a unit is held in each hand," Matsui said. "When you swing the unit in your right hand, it barks 'bowwow.' And you can make the sound 'meow' by using the unit in your left hand."
Because up to 24 units can be used at the same time, 12 people can play at the same time even if each of them holds two units.
Nordic's wireless communication IC adopted this time is the "nRF24LU1" on which not only a wireless transceiver but also a control circuit for USB 2.0 interface are integrated. The size of the IC is 5 × 5mm. And its top data transmission speeds are 2Mbps at the physical layer of the wireless system and 12Mbps with the USB interface.