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(...) This is a great idea except for one very important item: there is no such thing as a broadcast message (ie: a message sent to everyone) using Bluetooth. So for any such system to work, each robot has to know about every other robot, and send (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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The problem here is the management of a single shared resource, i.e. the air through which the ultrasonic signals travel. The lack of a Bluetooth broadcast mechanism makes the implementation of a conventional resource locking system difficult, but (...) (18 years ago, 21-May-06, to lugnet.robotics, FTX)
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| | Re: Ultrasonic sensor interactions
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(...) How about a single computer that was Bluetooth accessable. The server could act as a "lockable" resource that a NXT could acquire prior to doing the US detection. Then the NXTs don't need to know about each other, just the main server (and it (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) The 'Aloha' protocol was the predecessor of this. (...) Someone earlier told us that the thing runs all the time and can't even be shut off. That being the case, I think we're pretty much doomed. (...) Yes - but the relatively low frequency at (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) The device operates at 40kHz, the transmit and receive piezo devices are only resonant at that frequency. Even though the measurement period is short (time from transmit to time to receive) it is necessary to wait quite a while for the sound (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) Wow! That's a lot lower than I'd have expected - at that frequency there is a good risk of harmonics from normal sound interfering with it. (...) Right - 350 meters per second is pretty slow by computer standards. (...) (Not to mention things (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) I was the one that mentioned that I couldn't find a way from the SW I have to turn the US sensor off. That said, I don't think it's time yet to worry about intractable problems: A hundred of us or so have been playing with this stuff for a (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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I've heard of one possible answer, though don't know if it is feasible on the NXT. If the robot software sends timed pings, regardless of time of flight, they will be returned with the same delay between them. So if you send two pings 73 msecs (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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Hello Brian, (...) That's easy to do in NBC, and not hard with NXT-G: to shut off the US sensor, just "use" another sensor type on the same port. Here is a sample program that switches the US sensor on/off with NXT enter button. (URL) If the sensor (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) I'm not positive of that. If the US sensor is plugged in to a powered NXT, I can detect a clicking from it - I presume it's on. Regardless of what sensor I define the port as, this clicking continues. This is what I was basing my "can't turn (...) (18 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) Within the same room - is unlikely to be a problem - but think about two Sumo bots trying to find each other or two robots doing some kind of cooperative tasks in a contest or something...not likely to be so easy I think. (18 years ago, 22-May-06, to lugnet.robotics)
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(...) Agreed... perhaps surprisingly, based on dozens of hours of testing, with 1) sumo bots with a ring of sonars on all sides 2) Lego bots with two sonars on the front, we found no discernable problem. This is an anecdotal report, but the (...) (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) Sorry Brian, you are right! my ageing ear was not able to get the much weaker "ping" at first. My interpretation (to be confimed) is that the US sensor goes on working even if not configured, but some sensor modes don't provide the 9V supply (...) (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) I'm not sure yet; I admit to not being even remotely a "hardware guy", which is why I keep doing all this SW testing :-). (...) Another odd feature is that the ping frequency seems to change with both what you define the sensor as well as (...) (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) OK, and since I'm one of the few... I sent up a stationary NXT with an US sensor, and a "target" NXT with an US sensor as well, pointed directly at each other. Furthermore I had the "target" move back and forth to vary the range slightly. I (...) (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) OK, verification done, the voltage is correctly switched to 5V with the touch sensor. I probably programmed a wrong port# ! But clearly the 5V is enough to power the US transducers (probably with reduced range) Philo (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) ; us_off.nbc ; ---...--- variable declarations ---...--- dseg segment ;------- definitions ------- TCommLSWrite struct Result sbyte Port byte Buffer byte[] ReturnLen byte TCommLSWrite ends ;------- declarations ------- thePort byte 0 // port 1 (...) (18 years ago, 22-May-06, to lugnet.robotics)
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(...) I can confirm that the 0x2, 0x41, 0x0 "off" command does, indeed, turn off the clicking sound that you can hear coming from the US sensor. I can also confirm that the 0x2, 0x40, 0xNN "set measurement interval" command does set the measurement (...) (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) Excellent! Thanks for the update, and it's great to know this is availible within the HW. I wish NXT-G had access, but... well, either it eventually will, or LEGO has specificly included goodies in the FW just for 3rd party environments. (...) (18 years ago, 22-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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Hello John, (...) I have played with this command, it seems that only the low nibble of paramater is useful. The interval range goes from 12.5ms for 0 to 3s for 0xf. Interval seems to be roughly proportional to the square of the parameter. I have (...) (18 years ago, 24-May-06, to lugnet.robotics)
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