Just an addition, to my understanding; volatile also tells the c compiler that the value of a particular variable can be changed externally to the program (i.e: in an interrupt). Without declaring volatile, the value of a variable that changes only inside an interrupt will will "optimised" to a constant.
Thank you very much! I did not understand why a *delay()* command does not work in my timer interrupt subroutine, and spent many hours for troubleshooting until I luckily found your video and you explained it very clearly at 12:09.
@@LewisLoflin Hi, thank you for your excellent videos! Just one note - your myDelay(int x) routine actually delays for one more millisecond than indended, since the variable i is going from zero. Should be for (int i=0; i
Lewis Loflin OK, I was wondering if you were pulling down. Useful to note that I think the 328 data sheet says pulling down is more reliable. Thanks again. (While I have your attention don’t forget to make the trailing edge phase control video ...Greatscott has done one recently, but the subject needs the LL treatment!
@@whitefields5595 Thanks. One can only pull down if using internal pullups. Again this illustrated leading and trailing edge. I normally would use falling. Thanks.
I came here hoping to find out about interrupt registers... I came away having learnt what volatile actually does, and found out that Triacs and SCRs exist and what they are, and having learnt about phase controlled limiting of AC power output... I'm not complaining.
How about interrupts in software. How to do an ISR when, for example, specific amount of hardware timer ticks happened? Have you tried that with atmega328p (uno/nano)?
Hello Lewis Loflin i work for long time to understand pin change int but it doesn't work i want to have code wich use pin 7 (on arduino uno ) as pin change int to turn on and off led on pin 13
I would probably want to try a hall effect tach setup using interrupts to count rotations.. Is there a way to detect or calculate the shortest usable duration between events? Presumably you need some minimum processing time between interrupt events and when that goes to zero you are swamped!
***** The deal is while servicing an interrupt (ISR) other interrupts are ignored until a return is issued. If using say INTR0 and an interrupt comes in on INTR1 that will be serviced (if programed) afterward - but if multiple interrupts occurred on INTR1 they are lost.
+Lewis Loflin Thanks Lewis, I am just starting with Arduino. Ordered some Arduino cards, motors, micro switches etc. from China, waiting for them to arrive. I decided build an automated tea bag dipping machine for a first project :-)
OFF topic: Your UTube audio is weak and muddy on MAX volume! ........ Well it's back when I pull the headphone plug partly out. This has happened on two UTube videos tonight. Others are fine. It repeats on those same videos and makes absolutely NO SENSE! Anyone experienced this?
Lewis, don't make any updates because of my experience. When the audio came back (partly pulling the headphone jack) I could easily understand your voice. There is a bit of noise but not bad. The PC speaker works like it should! The reason I posted is this is a strange effect. It occurs at exactly the same places on those videos that display it. On one video the ad at the beginning is just fine but the following audio is bad. Although it is good on the PC speaker and a partly pulled headphone jack a fully inserted headphone has this inability to play some sections of the audio that otherwise is fine on the PC speaker. I am an engineer and want to know how this can be possible. Maybe the left and right channels are 180 deg out of phase on some audio and are cancelling each other? Just my first guess.