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In lugnet.robotics.rcx.legos, Steve Hassenplug wrote:
> ok, I have a real question.
>
> I'm interested in sending messages between RCXs using only the sensor ports.
>
> I've tested and found by switching between active and passive, signals can be
> sent, however, when the port is set to active, it is not powered 100% of the
> time (power is turned off to read sensor).
>
> Is there a way to switch the power on, and keep it on, until I wish to switch it
> off?
>
> Also, I only want this change to affect one sensor port, not all three.
Take a look at the functions ds_power_on() & ds_power_off() as defined in the
dsensor.c kernel file. When you've set the sensor to passive mode, you should
be able to manipulate the sensor power bits using these functions[1] or just use
the bit_set() and bit_clear() macros directly.
The bit numbering of the sensor ports is reversed in the hardware, so sensor
port 1 is bit 2, port 2 is bit 1, and port 3 is bit 0.
> Finally, can someone tell me how long the sensor power is off, when reading an
> active sensor?
Typically 30us, however, the 1ms system timer interrupt can block the sensor
interrupt handler from repowering the sensor for up to 550us!!![2] If you're
using one of the suggestions that Joe Woolley or myself put forth on slowing the
sensor sample rate, then the 1ms timer interrupt won't be a problem, but you can
still have delays with the serial IR interrupt handler when sending & receiving
IR messages.
Mark
[1] I say "should" because I don't think I've ever tried this with BrickOS but
I'm basing this on a quick look at the dsensor.c file. :-)
[2] When an LCD refresh operation *and* a task switch occur on the same 1ms
interrupt.
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| ok, I have a real question. I'm interested in sending messages between RCXs using only the sensor ports. I've tested and found by switching between active and passive, signals can be sent, however, when the port is set to active, it is not powered (...) (20 years ago, 5-Jan-04, to lugnet.robotics.rcx.legos)
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