Comments on: A Tour of the Arduino Internals: How does Hello World actually work?

By: Bryan Taylor

Bryan Taylor — Sat, 21 Sep 2013 17:08:07 +0000

Hey Greg. Great post. I’m often left wondering when (reading through someone else’s arduino sketch) what these little secretive code snippets with bits, bytes and masks mean. You’ve gone a long way to explaining how the pieces of the puzzle fit in this post. Your writing style is also easy to read (though I sometimes find myself wishing for a picture or a diagram…).

If you ever get the time (I know that the prescaler of life takes a lot of the clock cycles away…) I’d really love to see posts that explain more on how to follow higher level functions and macros back to their roots in the header files, and also how to look at a pinout diagram and begin to use it with bits and bytes. There’s a lot more I’d like to know now that I’m thinking about it, but I’m sure I’ve already hit my quota.

Thanks again. Being a nuts and bolts guy, I like the inner details of how things work.

By: micah epps

micah epps — Wed, 11 Sep 2013 19:59:40 +0000

I don’t usually bother leaving a comment while trolling for info on the net, but WOW. I do like this level of detail. Thanks for sharing !!

By: Jeff

Jeff — Mon, 17 Jun 2013 03:42:18 +0000

hmm, code snippets seem to be missing…

By: Ake

Ake — Tue, 14 May 2013 09:27:04 +0000

Thank you!

There’re not many people in this world understand this, and it’s lessen that those who understand share it to other people.

ขอบคุณครับ

By: fabelizer

fabelizer — Sat, 13 Apr 2013 00:44:46 +0000

Very nicely done! It took a while to find it, but a great article!
@MurphySquint: X is a place holder for the Arduino pin number you will connect to your reset pin.
digitalWrite(X, LOW); tells the Arduino to send a low to the pin, putting your IC into reset as soon as…
pinMode(X, OUTPUT); makes ththe pin an output.
Delay(100); tells the Arduino to stay like that 100 milliseconds.
pinMode(X, INPUT). tells the Arduino to now make that pin a high impedence so it neither is high or low.
For this to work, you need a pull up resistor from your reset pin and Arduino pin to +5V. A resitor in the range of 4.7K to 10K ohms would work well. The code assumes your IC reset pin is active low. In other words, the IC works normally when the reset pin is high (5V), and the IC is in reset when the reset pin is low (0V).
-fab

By: MurphySquint

MurphySquint — Sat, 29 Dec 2012 01:20:12 +0000

Your knowledge level is just what I have been looking for. I have posted the following on several sites but so far no luck getting an explanation to my question.
How do I use an Arduino to switch another IC’s pin (reset) to ground?
I am trying to turn an IC’s reset pin to ground with an Arduino. It is a 5 LED array that has an IC controlling several flashing modes. I need to reset the IC to change modes and I want to use an Arduino Nano. I have seen an explanation setting an digital pin to input and then making it low and then setting the pin to output but I don’t understand the process. Supposedly it simulates a momentary push button switch using an Arduino.
Here’s the code that I have been given but I totally don’t understand how it works.
pinMode(X, INPUT);
….
digitalWrite(X, LOW);
pinMode(X, OUTPUT);
delay(100);
pinMode(X, INPUT);
I guess I need a very thorough explanation for someone from the slide rule era.

Thank you in advance.

By: Wengu Zhoudong

Wengu Zhoudong — Sat, 30 Jun 2012 10:03:26 +0000

Thank you for the interesting written. I am wondering if you could provide the explanation for VB. As you probably know, VB is used much more than the ATMEL softs and I think it could be possible to make the VB example instead of the ATMEL.

Thank you!

By: Martijn

Martijn — Fri, 29 Jun 2012 06:52:26 +0000

Code snippets seem to have disappeared again. So sad.
But what a great article! I’m keeping the link on my site for reference.
The only thing that still mystifies me, however, is the mechanism by which the right bit in a PORT register switches on a voltage. In other words: how is this “software-controlled relay” implemented? I miss this last step in this “all the way to the metal” story.

By: Lutieri

Lutieri — Sat, 02 Jun 2012 22:00:35 +0000

very nice article. neat and clear explanations. looking forward to more!

By: greg

greg — Thu, 02 Feb 2012 05:47:58 +0000

I fixed the code snippets earlier this evening. Sorry it was broken so long everyone! It was hard to fix!