Friday, February 15, 2008

Another design flaw in the LPF RC Receiver

After the news about a first design flaw on the LEGO Power Functions (LPF) RC Receiver at Eurobricks [1], which prevents it to be used with a classic 9V battery box [see end of this post], just another design flaw seems to have been found.

Don't know whether it is official or not, but the info below was posted at Lugnet [2].

TLG has just released the following information:

"We have been testing the LPF RC Receiver today and discovered an error in the RC Receiver firmware or chip masking. A register is not addressable. It affects all the set, clear and toggle commands for single pins....and only these commands.
We will do an update of the chip mask at some point (not too far into the
future). At that point it will be corrected."

While this is not catastrophe, it is a significant drawback that prevents the short term usage of 'single pin mode' applications. It could delay the release of other PF elements applications from OEMs who may had features like this under consideration (now that the LPF protocol is open source), for development of new products.
The same applies for LEGO itself. But as written above, the solution is just at their hands for when they want to put a fixed design in production.

At least LEGO, should learn that as the technology used in products and complexity increases, the effort put on testing them must also increase accordingly.

Personally I'm convinced this 'single pin' operation mode, could be of great use to control devices other than motors, like LEDs and simple actuators. Hope to see them in the future PF Trains line... ;)


krimpie said...

I am quite confused as to what the problem is with the reciever. What is 'single pin' operation mode? I am guessing that it refers to being able to change the direction of 2 different motors, even though both of them are attached to one, not two ports, but I am probably wrong. If it is possible to do that, it would be great, as the main problem with pf is that it is not designed for normal rack and pinion style steering, so I have to attach two XL motors to one port on the IR reciever, meaning thta I have to do some fancy gearing to get them to go in the same direction. And if you change the now open source PF firmwware, how exactly do you upload it to the pf battery box? It is no usb outlets to plug it in... Sorry to ask so many questions, but I am quite confused :)

TechnicBRICKs said...

Maybe if you read the LPF RC specifications, it comes more clear for you.
You have 'Single Pin Mode' and 'Single Pin Timeout Mode', both working on the same principle, except the second one clears the output automatically after 1,2sec.

With single pin you can control the signal that's put on C1/C2 pins individually. This intends to control simple devices like LEDs that require just one pin control while the other is fixed at 0V or 9V.
That's not the case of the motors, because you need two controllable pins (C1 and C2), so the motor direction can be reversed.

The PF firmware is not something you can change by your own. It something that lies on the chips chipmasks.
Protocol specification was just made open-source, so other vendors may develop their own devices, compatible with the LEGO ones and extending the functionalities actually available.

TechnicBRICKs said...

If 'Single Pin Mode' would be used to control to independent motors at the same port, they would be able to move just in one fixed direction or stop.

Alex Campos said...

Oh my dog... did LEGO get bought by Microsoft?

Anyway, I hope they make the the revised receivers discernible from the old ones; like perhaps a red switch instead of orange, or different assembly details like the two 9V geared mini-motors. Having a bug-free receiver may be critical in a future application.

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