6:55 "ISR" is the "Interrupt Service Routine", ie the code that runs when the CPU gets an Interrupt. what you meant there is called an "IRQ" which is the "Interrupt Request" signal that goes to the CPU and causes it to run the ISR (if interrupts are enabled).

As a convenience and to exemplify the behavior of the timer: LEDHZ = 1 TCNT = 65535 - (F_CPU/1024)/LEDHZ

Your videos are extremely helpful and educational. I can not express my appreciation for your work in words. Thank you very much. I have a small request, if it is possible please archive your twitch streams on youtube.

Thanks for this. Can you please do this same thing with another processor, say an SAMD21 or RP2040? I have used up all 6 ISRs on the 328P and need more, but can't understand the datasheets of the Cortex M0+ processor.

i didn't know your channel, but i instantly loved the fact that you started the video saying: "low level GANG".

I'm a full stack developer who did embedded systems as well in varsity and enjoyed it, however due to the nature of my work I haven't been writing much C since college but this channel has gotten me practicing again and my skills have level up 10 fold..Thank you so much for your A - Grade content 🔥🔥keep it up and I'll keep recommending you 🙏 also can we get some esp8266 mesh network projects?

I was just searching for this for a school project! Great timing!

I didn't know it was on 16-bit overflow condition, I thought the timers counted down and on zero the ISR was called. Thanks for this!

Really you should use OCR1A and OCR1B registers for the timer value and set CTC mode for timer 1, rather than setting TCNT1=0 in the ISR. That will get the hardware to reset the timer to zero for you immediately it matches the programmed OCR value. As your code stands there is some latency between the interrupt being triggered and your ISR getting called, so you will not have “exactly” 15KHz (or whatever frequency division of the CPU clock you are aiming for). Worse, if other interrupts preempt your service routine, you will also introduce drift with a manual reset.

You can also use the CTC modes and set the OCR1A or IC(i forgot the rest of the register name) and use their corresponding ISRs to do this task without fussing around with the timer counter itself.

Thanks I have some code I did ages back using the timer registers but I don't think I understood what I was doing as well as I do now with your explanation. Still... it did at least work!

Hello this was a very informative video but i would like to know if there is any difference between bare metal AVR C an CMSIS in the case of ARM processor?

Great Video, but i think you should always mention or show the specific part in the manual where you get the needen port and interrupt specifications from, its very hard to follow these low level stuff otherwise for beginners. Reading the documentation in the video would also teach your audience how to read these docs properly. Which is a higly needed skill to have if you are programming bare metal stuff.

Cool baremental programming technique! I think one the pros of interrupt-driven is power save, maybe you can upload another video to explain it.

thank you so much. if I want to have three timers so what part of the code will repeat? i suppose I would have to change 1 with 2 and 3 in TCNT... and also an ISR should be set for every timer. could you make a bare metal programming video on I2C and another on U(S) ART for the Arduino chip?

great tutorial, hope to see more like this !!

Wow reminds me of my university days learning how to program a Microchip in assembly.

Oh damn, your makefile... I recall taking some massive makefile for raw AVR programming and distilling it down to a nice hand written makefile like that and it was so much cleaner. But I lost that thing years ago and didn't want to recreate it 🤣, very glad to see you have a MUCH nicer starting place

Being raised on 6502 and watching SEI for actually enabling interrupts makes me feel dizzy a bit ;p But video is as clear as it could be, guess that anyone who understands bitwise C operators and concept of interrupt handler will take benefit from this video, thanks!

I don't know why I'm watching this, I have no clue what's even going on lol

i always learned to do it with timer compare that way you dont have to do the subtract but its just a different way of doing the same thing :)

would it be possible to explain this for arm ?

Nice video, keep it up!

Is it possible to put the CPU to sleep instead of spinning an infinite loop?

When I wrote my space invaders rip-off on the AT328 I got a stable framerate by using this interrupt by putting at the end of the frame loop a _while(variable){ }; variable=1;_ and then in the interrupt I set variable=0, so I would just loop there until the interrupt kicks in. I don't know if that's the best way to do it tho.

Great vid, but I did notice one problem, the Egyptian Braces in your int main :P

I used to program the 2560 in the old AVR Studio, its simulator was pretty good and useful, but nowadays I do prefer to program it like this.

Nice, easy to understand. I would still suggest adding more comments about the register assignments for easy lookup but the video is short enough to rewind. Wouldn't it make sense to also use a macro since we were the same code twice for TCNT1? (In the end both the compiler might precompute the constants into a single value so this would only be for the human reader.) On the other hand, the TCNT1 assignment in main() is basically setting the first delay. Can we just set it to 65535, as basically an almost zero delay to just not worry about it? Or is there a chance that the timer will tick "too fast" in the background if there is more setup code in main() before the sei() call, so the initial value will overflow and need to increment the total amount before the first "interrupt routine" is being run?

If you had something like a TL866 chip programmer and the 328p was removable, could you just dump the hex file directly onto the microcontroller?

Thanks for the helpful video. 2 things I had to google: Do CS10,CS11&CS12 change a lot for different avr chips? Else wouldn't TCCR1B = 0b101; be clearer? maybe that is just me. Is using _BV() to show different methods to do the same thing or would (1

Is there a reason you use _BV() sometimes but not other times?

How to compile Rust for Risc-V?

It would be worth including a comment about how the interrupt flag gets cleared. In many micros you have to do it explicitly but I am guessing the Atmel clears it automatically when you reload the timer. A common mistake used to be forgetting to clear the interrupt flag.

You should have also put the CPU into one of the sleep states to conserve power.

I am having trouble with flashing the code using avrdude: avrdude: stk500_recv(): programmer is not responding. I am on Linux Mint, 64 bit.

What increments TCNT1?

Instead of XORing PORTB, PIN5 to toggle, just write a 1 to PINB5. That will toggle for you. Cheers, Norm.

Like to see the same type of info for ESP32 boards

Buildroot & Flutter app tutorial, please 🙂

Instead flooding the CPU with "push" and "pop" with using interrupts, you should start coding in a sequential multitasking style. Using a few interrupts is no deal for most conditions. But using interrupts for every single task you have ends up in wasting very very much time executing "push"s and "pop"s. Just have a look at the assembly output from the compiler. You are right, sleeping the CPU with delay() is waste of time, but using interrupts as a global task worker results in a lot of time waste as well.

Your github repository seems to be missing some code in main() ;-)

Bear... metal (laughs) I do that infinite loop as `loop: rjmp loop` .... always want to "dare" C programmers to use a goto. ;)

Is your Sublime Text Unregistered?? 🧐

after using stm32, AVR just feels so underwhelming in every thing :P

I need deeper knowledge about atmega 328p

Should it be "by using Arduino Timer Interrupts"?

You lost me at 8:57 I don't get how that becomes a second

great, now go to sleep() instead of while(1) nop'ing

Second