This section tries to point out several
questions, topics and potential problems about sensors, wireless interfaces and
use of the WiSe Box.
Q. The sensors connector is not
practical at all / terribly awful ! Why not using mini-jacks ?
A. Because size DOES matter ! The WiSe
Box has been designed to be portable, and individual connector would triple the
size of the box. More over, when attached to a costume, plugging sensors
individually before performing is a nightmare while having just 2 plugs to
insert is so easy.
Q. Why don’t you provide a pigtail cable
?
A. Because there is no standard for
sensors wiring / plugging. It has to be done by the user whom chooses which is
more adaptable to the sensors he might already own, and also much cheaper. A
pigtail cable has to be done manually and our “huge” team of 2 people cannot
afford it neither time wise nor money wise.
Q.
Whaow ! This device draws a lot of current !
A.
To maintain a reliable radio link with such a rate (11 Mbps) and range, some
power is required. A professional wireless microphone behave the same way and
its autonomy is about the same as the WiSe Box.
Q.
Why not using a classic 9V battery ?
A.
Because it cannot provide enough current for the box. A 9 volt battery can only
provide about 160 mAh. Moreover, such a voltage is not needed since the WiSe
Box works at 3.3 V. The 4 AAA batteries (eq. 6V with alkaline ones) provide the
best compromise between autonomy and power efficiency ratio.
Q.
Why not using an internal Li-ion battery ?
A.
For many reasons. First, they cannot be bought so easily because their charge
as to be controlled very carefully, if not, they simply explode. A device
powered with such a battery has to pass a lot of tests before being authorized.
The second reason is that when the battery is old, it has to be replaced, which
costs a lot and it means that we need a battery stock. Unfortunately Li-ion
batteries do not support long term stocking (> 3 months). Last, and most
important point : when the battery is discharged, your WiSe Box is locked up
for the rest of the rehearsal session.
It is much simpler to put in a set of charged batteries, or to run to
the closest drugstore to buy regular ones !
Q.
Why didn’t you implement a charger in the box ? / Why is it not USB
rechargeable ?
A.
See last point of the previous question. Moreover, external battery charger are
inexpensive and can charge several sets of 4 AAA batteries at once.
Q.
My WiSe Box does not start when plugged in my USB hub ! I get a message like
“USB : This peripheral draws too much current”
A.
The WiSe Box consumes about 290 mA. A native (i.e. on the computer) USB port
can provide 500 mA while a non-powered hub will dispatch a maximum of 100 mA
per device only. You can either plug you WiSe Box in a native port or add a
power adapter to your USB hub.
Q.
This device is particularly complicated to configure ! Why not having a simple
auto-installation ?
A.
Because the WiSe Box is a network peripheral and has to be setup in a custom
way depending on the Operating System / Computer / peripheral combination of
the user. Moreover, the WiSe Box is very versatile and can be used in many
different ways. Configuration has therefore to be adaptable and might be
tricky.
Q.
This serial port USB driver is difficult to install / manage / understand… Why
not having a dedicated and straight driver for the WiSe Box
A. Because we don’t know how operating systems
and hardware will evolve. Our main design rule is not to re-invent the wheel.
Therefore we implement in our hardware functions designed by specialized
companies, such as the USB serial port. FTDI provides the technology, drivers
and installation guides and supports the product for future evolution of the
Operating Systems.
Q.
The 2.4 GHz band is pretty busy ! (WiFi, BlueTooth, A/V transceivers) Do you
think it is reliable ?
A.
Yes… and no ! Using wireless devices is ALWAYS risky, however, several points
can make wireless more reliable. First of all, a free radio channel has to be
selected (See “Security Issues” paragraph). BlueTooth has a frequency hopping
system which automatically uses non occupied radio channels. As a general
remark, using radio for Live Performance requires an identification of the free
radio band available in the performance space, as it is achieved for wireless
microphones. The 2 goods points are :
Q.
When I have no sensors plugged, I receive a non-zero value in my software. Is
it normal ?
A.
It is perfectly normal. The WiSe Box digitizes analog voltages on 16 bits
(65535 steps). Its sensitivity (voltage quantification) is therefore 3.3 V /
65535 = 50 µV. The internal analog hardware features a normal offset of 3-4 mV
(0.1% of the dynamic range) which correspond to [80-100] digital value. We
preferred not to suppress this by the WiSe Box because :
§
It would have been kind of “cheating” about the real
specifications of the device. A NULL offset does not exist !
§
It wastes CPU power to “suppress” the offset inside
the WiSe Box. Our main concern is the quality of the sampling and the data
rate. A simple use of scale and clip in Max/MSP will shape your
sensors’ data the way you expect.
Q.
Digitizing sensors is nice, but how about having OSC to DAC/CV ?
A.
It is totally possible, but not for this product. Actuator and Continuous
Voltage control / generation through OSC needs might be different from a user
to another, which makes difficult for our lab to have a global answer. However,
our development OSC platform EtherSense provides a quite simple way to
build electronic daughter boards and to interface them with OSC through
Ethernet. Electronic and code templates for EtherSense Daugther Boards are
available on-demand.
Please visit : http://recherche.ircam.fr/equipes/temps-reel/movement/index.html
Q.
What is this strange “puzzle” icon you use everywhere ?
A. Does it puzzle you ? For us,
the WiSe Box was a kind of missing part for our multi-performer approach
and the puzzle piece also symbolizes connectivity with other entities.
Q.
When I turn the WiSe Box on, the LED stays red !
A.
The WiSe Box is protected not to start if the power supply voltage is too high.
Check your batteries or USB source. If you use a Mains Adapter with USB output,
make sure it delivers less than 6.2 volts (and more than 3.4 volts).
Q.
Can I plug a microphone in the WiSe Box ?
A.
Yes… and no ! The WiSe Box is a continuous controller to OSC converter. It is
supposed to be used with sensors that deliver low frequency and positive
signals, which is not the case of a microphone. However, with some electronic
circuitry, a microphone can be turned into a pulse detector or tap tile. To
digitize a microphone, the appropriate device is… a sound card !
Q.
Can I track the pitch of an audio signal with the WiSe Box ?
A.
No
Q.
Is it possible to be connected to the Internet while using the WiSe Box
A.
Yes, if you are using Infrastructure Mode with an Access Point which is also a
router / gateway. In the LAN properties of the Host Computer set the Default
Gateway and DNS address to the router IP (default is usually 192.168.1.1). In Ad-hoc mode, Internet access should be
achieved by connecting the LAN adapter to your DSL modem. Be sure to have the
WiSe Box & WiFi adapter IPs on a different class than the LAN & DSL.
Q.
Why not using DHCP ? IP configuration is so boring / complicated !
A.
Using a simple DHCP makes identification of the WiSe Boxes on the network
impossible since you cannot predict the IPs affected to the WB, disabling OSC
monitoring of individual WB. Even if configuring several WB takes a bit of
time, further configuration is not needed after proper setup.