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Kekoa Proudfoot <kekoa@pixel.Stanford.EDU> wrote:
> Maybe the light sensor just does not receive IR light like you expect it
> to, despite your experiences with the IR remote? I will try to write a
> program to do what you seem to be trying to do, since it will only take a
> few minutes or so to do that.
So I just tried this, and it took more than a few minutes to get it to
work. But it does work.
Apparently, the modulation of the IR signal is needed for the light sensor
to give a reading. The standard modulation used during regular IR
transmission is sufficient. I used the following code to set up the IR
signal:
/* Set TxD to output */
*(char *)0xffb8 = *(char *)0xfd84 |= 1; /* Set port 5 bit 0 to output */
*(char *)0xffb6 &= ~1; /* Set port 5 bit 0 to low */
/* Set up 38.5 kHz modulation */
*(char *)0xffd0 = 9; /* clear on compare match A, div 8 */
*(char *)0xffd1 = 0x13; /* toggle on compare match A */
*(char *)0xffd2 = 0x1a; /* 26 cycles for 38.5 kHz carrier */
/* Set range to long */
*(char *)0xffb5 = *(char *)0xfd83 |= 1; /* Port 4 bit 0 output */
*(char *)0xffb7 &= ~1; /* Port 4 bit 0 low */
I then polled the sensor and updated the display with the raw value as seen
by the a/d inputs, using a/d code that is similar to that used by the
firmware but much different from LegOS, as explained in a previous message
to this list. I saw typical raw values around 750, with readings
constantly fluctuating between around 400 and 600 at several to tens of cm,
and a mostly constant reading of around 315 at 0 mm from the IR filter at
either side of center.
-Kekoa
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Message has 1 Reply:
 | | Re: Blocking IR
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| In addition to what I mentioned in the previous message, I also set the sensor input port to active. Setting it to passive also works, in which case the ambient light level seems to be around 480-495, and the sensor aimed directly at the IR port (...) (25 years ago, 21-Jun-99, to lugnet.robotics.rcx.legos)
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Message is in Reply To:
| | Re: Blocking IR
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| (...) I doubt you have a broken RCX. If you did, firmdl.c would not download firmware correctly. (...) That is a good thing to try; I suppose it did not help things? (...) I don't see why you couldn't post the .srec file. I don't know if you also (...) (25 years ago, 20-Jun-99, to lugnet.robotics.rcx.legos)
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