Problem capturing 'One Shots' Hardware or Software (or both?)
acmg
Posts: 2
I have been trying to deal with 'spurious interrupts' in an Arduino based anemometer. (yeah I know I should use a Propellor and avoid interrupts all together but the learning curve is greater). Anyway, the anemometer is just a spinning magnet which periodically closes a reed relay. I use that to pull down an input on the Arduino. Sometimes I get interrupts much too close together probably caused by 'noise' on the roughly thirty feet of telephone wire. I figured I would use my Propscope to look at the signal before designing a hardware filter . My propscope was finally persuaded to do the job (sometimes) but is very temperamental and reports absolutely crazy measurements more often than not. The Arduino runs off USB voltage 5 volts. I set the trigger edge to 'Fall' and level to 'normal' ( I have quibbles with propscope's 'auto' setting but I digress) In general I can see propscope updating its measurements every second or so . If I am very careful I can get several valid displays, but ultimately propscope 'freezes' (the one second updates disappear if triggering is turned off). Then it gets strange, to 'reset' propscope I hit the 'run' button or hit F9. Requesting a 'Load firmware' often will cause a 'click' in propscopes relay(s) and then either 'unable to find propscope' or it comes up but displays both C1 and C2 at -8 to -9 volts ! ( an interesting trick as C2 is tied to ground and the Arduino does not to my knowledge entertain negative voltages). Pulling and re-inserting the USB connection and restarting Propscope clears the situation. When playing the devils advocate and trying to look at 50 ns timing I often get a blast of noisy readings reporting very high voltages followed by the dreaded lock up. Does anybody have any ideas as to what is happening? .
doc
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