| Communications | |
| This page is divided into the following subtopics: | |
| IR Tower Info | |
| IR Tower/PC to RCX Communication | |
| RCX to RCX Communication | |
| RCX to IR Tower/PC Communication | |
| Other (Palm Pilot to RCX, etc...) | |
| IR Tower/PC to RCX Communication | |
| RCX to RCX Communication | |
| This is not a problem,
but if you use the standard firmware you are limited
to one byte transfers. If you roll your own code to do this
you can do pretty arbitrary stuff modulo general reliability of IR
communication, which can be flaky depending on your
lighting environment, orientation of RCXs, etc. I
think LegOS might include some useful general IR code, but I am
not sure.
-- Thanks to Kekoa Proudfoot
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| RCX to IR Tower/PC Communication | |
| RCX->PC is difficult
because of the tower hardware. The tower shuts off a
few seconds after it completes transmission to save power. Messages from
the RCX that arrive during or after the shut off are truncated or not
received. The tower works best in request/reply mode where the PC requests
something and the RCX replies to it. In request/reply mode, a good
practical cap on the max number of data bytes to transfer from RCX to PC
in one go is 256 (does not include header, complements, or checksum).
Larger sizes might work, but I know 256 works. When grabbing the ROM
image, I distinctly remember having to reduce the size to avoid losing
data to the tower shutting off. I ended up using the 256 size.
-- Thanks to Kekoa Proudfoot After you get some data, like 768 bytes or something, send another signal from the PC. The RCX waits for this, and then sends another 768 bytes. This should keep the tower on for the right amount of time. Also, be careful of sending too much data, increasing the duty cycle, and burning out the IR LED's in the tower or RCX. They can be replaced, but it is probably hard. -- Thanks to Andy Gombos
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| Other Forms of Communication | |
| IR Tower Info | |
| The tower converts an
RS-232 serial transmission directly
into IR and vice-versa. -- Kekoa
Proudfoot
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