Subject:
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RE: TLG & MIT Media Labs spawn another product: PicoCricket
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 31 Aug 2006 14:46:39 GMT
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Reply-To:
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<DICKSWAN@SBCGLOBAL.nospamNET>
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Viewed:
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3229 times
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On Thursday, August 31, 2006 7:03 AM danny staple wrote:
"Question - does anyone know how many output or input modules could be
attached, and if there are any plans for seperate motor control
boards? I strongly agree with Brian that having the motor controller
separate from the mainboard could be quite handy."
The PICO cricket had four ports. The ports are interchangeable -- you
can connect either inputs or outputs to the port. And any device can be
plugged into any port and the PICO cricket will find the device!
Each peripheral device is intelligent and equipped with its own small
microprocessor. There's a standard bus between the PICO cricket and the
devices. This common bus is used for both sensors and motors. There's a
good description of the Cricket bus somewhere on the MIT web site and
presumably this is what PICO has used.
From memory, I recall the bus as proving power, ground and a half-duplex
serial link. The packet protocol on the bus included an address field,
so it should be possible to daisy chain multiple items on the bus
although the PICO cricket does not have the mechanical capabilities to
do this. The bus was fast -- 100s of Kbits per second. THE MIT paper on
the protocol was particularly "proud" of the design innovation allowing
a bit-banged implementation on small micros that did not have hardware
UART -- I recall they stretched the 'start' bit.
The motors/sensors have self-identification capabilities. For example,
if you program a motor, it works whenever the motor is plugged into any
of the four ports. The self-identification is the "type of device" and
not an address.
For example, the base kit comes with two light outputs. If you do
nothing when you send a light control command then it is sent out over
all four ports. The default action is that a command applies to all
ports. There is a feature that allows you to specify that an
input/output command should use the single port specified.
The ports use a funny little connector. It looks like the same physical
shape as the tiny USB connector used on my digital camera. Logically and
electrically it is not US.
PICO cricket devices have features you can't find on the NXT. It has a
really neat user controlled light output; it looks like a tri-color LED
with variable intensity for each color. It has better sound playback --
you can select from 24 different instruments: piano, trumpet, bells,
vibe, rooster, horse , etc). Rooster/horse? -- remember this is a kid's
toy! You can also control the tempo (playback speed. 100 steps) and
volume (100 steps). You can also define your own tune/melody for
playback.
Two PICO crickets can message to each other by "beaming" infrared
packets between them. This is not the 'crippled' low speed IR found in
the RCX. I think it is much higher bandwidth.
Yes. I too think it would be neat if the PICO cricket devices could be
connected to the NXT. There seems to be two approaches:
1. Develop a new NXT "sensor" to beam IR packets to a PICO cricket.
2. Develop a new NXT "sensor" that contains one (or more) of the PICO
cricket connectors. There's probably a powering issue -- especially
with motors.
All power to ports is supplied from the main PICO cricket. It takes
three batteries (AA I think, but maybe AAA -- I can't remember). So I
think the motors are maybe a little underpowered for use in a Robot. It
only supports legacy LEGO motors.
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