Thursday, March 4, 2010

LEGO Power Functions RC Protocol v1.20 update

Today LEGO released a new version from the LPF RC Protocol document.
Now in its version 1.20, which can be downloaded from here.

After having analyzed the document, the main changes seem to be:

  • Removal of "Single pin continuous mode".
  • Removal of "Single pin timeout mode".
  • Some commands addition to the "Single output mode". As it seems this has also inherited equivalents to the commands from the first mode above (removed).

 Some questions that are now raising in my head, are:
  • Why were these modes removed?
    • For optimization and reserve space for new modes to come!?
  • Is it the "Single pin timeout mode" simply gone?
  • Reasoning for the negative logic at some "Single ouptut mode" added commands?
  • What have changed besides the protocol?
    • Does the RC Receivers will get changed too, getting us a 3rd version of them?
    • What about retro-compatibility? I guess the existing receivers will continue to answer to the modes now removed!?
  • Any other subtle changes in this new version of the protocol?

 ...clarification request addressed to TLG.

Having meanwhile studied the document again, I can say the both modes removed ("Single pin continuous" and "Single pin timeout") were incorporated into "Single output mode".

Also and answering to another set of questions above, one can say that the RC Receivers didn't get another change at the time.
It happens this new version of the document describing the LPF RC Protocol was intended to replace the previous one (version 1.10), which was released with errors. Thus the RC Receivers in production by then implement the protocol described in version 1.20, instead of 1.10.

Last Update: 2012.Jun.30 00:30 CET


mahjqa said...

Also; can anyone here explain what these modes actually DO?

Tristan said...

It would seem that the planned use of the Signal Pin mode is now dead. I think that might be a realisation that it had no use for them and so is redundant.

This is probably a major hardware redesign which is simpler and cheaper to make.(My opinion coming from an electrical engineering POV)

Anonymous said...

Could this update be part of the reason why the PF IR reciever is on backorder at LEGO Shop at Home?

-Toa Of Justice

Anonymous said...

Maybe TLG is trying to create the capability of controlling BOTH regular Power Functions components AND NXT components. See Philo's "Power Functions NXT Remote Control" webpage at .

JAMS said...

I'm with mahjqa, what does all this actually MEAAAAAAN

TechnicBRICKs said...

Sorry to say, but if you don't know you hardly need it.

This information is relative complex and until TLG decides to make own use of it, might be useful for:
- OEMs who might be interested in developing new PF compatible elements, once they take an agreement with TLG (I believe there is that possibility, like it happens with the MINDSTORMS NXT platform, despite the "non-comercial" warn in page 2 of this document).
- For Power users capable to program compatible IR emitters (e.g. NXT sensors) and willing to try dis advance modes.

There are many possibilities open by the modes in this document, from which I could give here one example from the newly added commands:
- Once properly programed it will be possible for an IR emitter and making use of "Single output mode" to generate a single-step increment or decrement to the speed of one PF motor, by the action of a single keystroke or lever actuation. This would be more reliable than actual PF Speed Remote control, designed to be used with PF trains.

There are many other commands and open possibilities.

TechnicBRICKs said...


I've two ordered since some weeks, to make sure I would get some of version 2.
Maybe I'll get directly version 3 instead, if it really happens to be a version 3 with these changes.

On the other way it may also happen the new HW version to be already including these latest changes together with the first ones and we getting them documented just now!?

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