But if real CPU computer is cheaper than the microcontroller, you may start comparing it... :-)

Except you want that thing to run on battery, or act in near real time.

Regarding battery: +1 Regarding real time: you can have it also on RaspPi!

Sure they are.

I mean, sure, you and I know the difference between an 8-bit micro with some friendly libraries and a 64-bit ARM SOC running a full OS. But for a lot of stuff they accomplish the exact same thing. So why not compare them by what most people do with them rather than their raw technical specs.

This is like saying a farm tractor and a pickup truck are the same thing because they both have internal combustion engines and wheels.

Yeah, but if the farm tractor was cheaper, faster, and could carry more cargo than the truck, why wouldn't you just use the tractor?

AVRs have much better sleep modes (single digit microamps) and predictable performance (to the exact clock cycle) by default. If you need long battery life or hard real-time performance then they're probably a better choice than the Raspberry Pi.

All reasonable responses in this thread to GP, but parent hits the nail on the head.

For non-hobbyist problems where you really need a microcontroller, it is selected by spec (in terms of performance, operational predictability, physical/material properties, power consumption), and then purchased in volume (~ millions). Employing a general-purpose CPU for said problem, while potentially alright when prototyping, would not be satisfactory.

True, however that's AVRs and not Adruino. You very quickly get out of arduino-land when you have any constraints like battery life or performance. By far the vast majority of people contemplating either Arduino or RPi will never know enough to be able to tune things like that.

Heck the last time I looked into doing sleeping on an AVR-based Arduino it basically said go look at the 328's manual to set the registers directly. (Although that was a long time ago.)

One abstraction layer above in fact. It's like saying a farm tractor and a pickup truck are the same thing because they both can move you from point A to B.

I was being charitable, as both are Turing-complete computing devices of similar physical size.

They're not the same thing, but unless you have some specific use case that demands a farm tractor and you concretely know why, you should go for the pickup truck.

The big difference here is power drain. With Arduino you can use the Atmel ATmega328 microcontroller, which can run for months on 2xAA batteries.

https://www.openhomeautomation.net/arduino-battery/

Higher source/sink current with GPIOs is also a selling point of the Arduino.

Sure they are not.

Different form factors, and most importantly different energy need. You'll get much better result running an arudino on AA batteries than a pi.

No, they are not. One has more in common with a FPGA, the other is literally a Linux computer. Different complexity, different skillset, different use case.

..Unless you're talking about something like the Arduino Yun, which actually runs a Linux OS. But as an example, you're probably not going to build a wifi security camera on the original device.

Yeah, but you're still talking about the raw technical implementation of how they work.

All I'm trying to say is that for the vast majority of users a raspberry pi can do anything that an arduino can. Sure you might not be able to so some super tight real-time stuff that you could do with hand-rolled asm that you could do on an arduino, but at that point you're more at the level of 'using an AVR' than 'using Arduino'.

When the problem is "I want to control some RGB LEDs" or something, either can be used. That means that they are of the same category.

A rackmount server can control some RGB LEDs, if wired correctly. That doesn't mean a rackmount server is in the same category as a Pi.

Furthermore, most people using Pis and Ardunios are hobbyists who are necessarily familiar with the raw technical implementation and are choosing the product based on that technical data.

Yeah, but if a rack-mount server was cheaper, easier to use, about the same size, and used a reasonable amount of power compared to an Arduino, I'd probably use a rack-mount server for all my DIY projects.

Digging into it, it looks like the Arduino and friends trump the Pi versus sleep/idle modes in terms of power draw, and that's likely useful for easy battery operation. If you're tapping mains power, it's likely a rounding error.

OTOH, all the folks saying the knockoffs are $2-10, that's cheaper than a Pi.

I needed a small box to run owncloud. I would definitely use something like a Pi (or odroid).

I needed to control my brewery's heating element based on input from a timer and a thermometer. That definitely called for an arduino.

They're different, and while it's true I COULD have used a Pi for the latter, it would use way more power and be complete overkill.

I think people are getting hung up on verbiage here. Yes, I realize they are not completely identical.

But, the original comment was taking about the price difference between the arduino and an RPi. Sure the RPi is 'overkill' for for controlling brewing beer, but if it's cheaper, then why not use it? I could understand this argument if the more-feature-full thing was more expensive, but not when it costs more for less.

Don't get me wrong, I love Arduino. I use it way more than I use RPis. I just use it on $2 ESP8266 boards straight from China.

All the projects I did with arduino could have been done with the pi. Some even easier to code because I could have used python. So when a full microprocessor based PC is cheaper than a microcontroller why wouldn't you use the better option. Again, I know there are certain things a microcontroller excels at, but most people don't use their arduino for those things.

Now if the arduino was 10x cheaper, the entire value proposition and application space changes.