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Having had a good look inside my RCX, I'm thinking seriously about what is
really possible in the same space envelope, whether extra ports or functions
could be added for RCX3.
I think it's useful for us to know what's inside the RCX, especially if we want
to have any input into what's inside the next evolution of it, which is one
reason why I've been looking into the circuits. Perhaps our ideas are more
likely to be taken seriously if we understand the constraints of the space
envelope and available electrical and processing power.
Much of the circuit board is quite densely packed with components on both sides,
and the board already has 3 track layers, so the only way to fit more ports in
(with the necessary components) would be to hybridise parts of the circuit.
(Hybridisation is where all the components without their cases (just the silicon
bits) are put together inside one package, miniaturising the circuit. The
resulting hybrid might be a package looking a bit like the processor).
I don't think the motor port circuit could be miniaturised, as the motor
controllers are already 90% of the motor port circuit and the diodes need to be
rated for more power, so they should stay as discrete components.
The power supply circuit, likewise, needs to be rated for power. The capacitors
are some of the largest components. Does anyone know if some of them (6x300uF)
been removed in the RCX2? Certainly we want the original mains input port to be
put back for RCX3, though this would require the same space as the RCX1 power
circuit.
The sensor ports could be hybridised. Each sensor port requires 3 transistors,
5 resistors and 1 diode, plus the protection diodes and capacitor, which would
have to stay as discrete components for power reasons. If the pull-up
components were included then all three (or more) sensor port circuits could fit
into one hybrid. However, the sensor port circuits surround the port connection
clips, so the hybrid would have to go elsewhere on the board.
The processor, ROM and Octal flip-flops (74HC377) could be made into a hybrid.
This would not save much space, but it might be enough for a sensor port hybrid
to fit on that side of the board. The processor has eight ADC ports, of which
three are used for sensors. Others may be used for power supply or motor
monitoring, but there may be another one free for a fourth sensor port.
The display is a finite size and already has its controller chip and the sound
device underneath it, so no space could be saved there.
The IR LEDs and receiver device need to be where they are, behind a window at
one end of the unit.
Summarising, there is the possibility that sensor ports or the main computer
parts of the circuit could be shrunk into one IC, as long as the components are
available in die form. Therefore some space could be saved on the circuit
board.
Given that there is a custom IC inside the RC Tower, the miniaturisation of
circuits onto ICs is not impossible. The question is more one of the cost
feasibility for a production run of maybe 300,000 units.
I think enough circuit board space could be saved for a Bluetooth IC to be
placed in the space. This would give the RCX the freedom to wander out of sight
and still communicate, which would greatly expand its roving possibilities,
including a colony of RCX robots interacting. I'd like to see a port for the
camera to be plugged in, so that this too could take advantage of the Bluetooth
capability, making a remote spy robot!
The port connection clips are within 8mm of the edge of the board, so four ports
of each type across the case width is not possible with the current scheme. The
control center uses leads cut in half with wires to the circuit board, but the
trend is away from this and towards the clips. I don't honestly think that any
more ports could be implemented in the same box, unless an alternative connector
scheme were used.
Those of us with greater robotic ambitions, requiring more ports, probably have
the skills to interface two or more RCXs into one robot.
In conclusion, I think TLC did a really great job of fitting as much as they
could into the box. With the addition of Bluetooth and the restoration of the
mains port, the RCX3 would have as much extra hardware functionality as
possible, given the advance in technology since the RCX1 was produced.
Perhaps, given the anticipated release date and the long programme to produce
the next RCX, our time to suggest new functions has now passed, but at least we
can understand the limits if not everything we want is implemented.
PLMKWYT
Mark
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Message has 2 Replies:
 | | Re: RCX3 - Can extra hardware functionality be added?
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| I've seen this topic come up several times, and am curious why no one suggests that the input and output ports be extended from the RCX to pods. Using the same form factor constraints limits the possibilities. Using a more condensed cable connection (...) (19 years ago, 22-Jan-05, to lugnet.robotics)
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