MinIMotion detector operation


New Member
I have one of the MiniMotion detectors. I have yet to write the SW to read the DS2405, but wanted to find out what to expect for output from the DS2405. From the DS2405 documentation page 5 it says each time the Match ROM command is issued the PIO pin is toggled and then it's logic state is returned. So, if there has been motion what is the logic state returned? (1 or 0) Would I also always need to issue 2 Match ROM's commands to return the PIO back to it's original state? or??

Any example interaction sequences would be appreciated!



For the Mini Motion Detector you would want to use the Search ROM command since it will return the state of the PIO pin without changing it. The DS2405 starts up with the PIO output off so as long as your code never sends a Match ROM to the DS2405 then the output shouldn't change.

The Mini Motion Detector will pull the PIO pin high for about 1 sec. each time it detects motion.

Let me know if that didn't answer your question.

So, if I don't poll (Search ROM) the DS2405 during that 1 second then I would miss detecting that motion? I may not be able to poll all devices I have and get back to the MotionDetector in time to catch the motion.

I have some of your Dual Counter devices I'm using to detect door openings with a mag. reed switch. All I do is poll them as frequently as I can and then if the count has changed since I polled last I know there has been a door opening since the last time I polled and I would know how many door opeings there have been sicne I last polled. (I save the previous total count)

I was hoping that with the MiniMotion detector that it would set a latch when motion has occured then I could detect that and reset it when I poll.

Looks like there is no work around to be able to 'not miss' detected motion by not polling frequently enough.

Any thoughts on this?


The Mini Motion Detector board can also use the DS2406 which has an alarm state that will let you know if there has been a change since the last time you queried the chip.

The reason I don't currently use the DS2406 on the device is because it is more than twice as expensive as the DS2405.

OK, thanks for the insight. Maybe a future design using the DS2423??? Works great as I described in my previous post. Not sure how the cost compares.

Thanks again....