Atmega 328P vs Atemga328-U

[samarth]

So I bought an atmega328 (those were my exact words to the shop keep), in a DIP package. I had expected it to be the more common (i think?) atmega 328P.
Turns out, it was labelled Atmega 326-U.
Is there any major difference between the two?
Or is it the same difference as atmega328 vs atmega328p?

Regards,
SR

[TimFox]

Is "326-U" a typo?

[golden_labels]

It’s 328 and 328P. Letters after the dash indicate the ordering code. For both of them, not only 328. The ordering code is internal to Atmel/Microchip and its meaning is not documented. While some have been correlated with packaging type, binning or delivery options, other remain a mystery.

You are mentioning an U code, which is not listed in datasheets for ATmega<X>8 series, but that’s not the first time such components surface. However, be sure to check if that’s not AU, MU or PU: those are QFP, QFN and PDIP packages.

[samarth]

Here is a picture of the mcu I bought.
I thought it looked like a U?...

[samarth]

You are mentioning an U code, which is not listed in datasheets for ATmega<X>8 series, but that’s not the first time such components surface. However, be sure to check if that’s not AU, MU or PU: those are QFP, QFN and PDIP packages.

Ref the image I had posted...
Also, I am not sure that the body is not made of plastic. It is DIP though.

Regards,
SR

[Rick Law]

Important to note however, their is one difference you may consider major  (I would) ...

The TQFP/QFN/MLF package has 8 ADC channels where as the PDIP packaging (the one you got) has only 6 ADC channels.

So, with the PDIP, you have ADC0 to ADC5 but missing ADC6, and ADC7.  If you use I2C, ADC4 and ADC5 are used for SDA/SCL leaving only 4 ADC to use.  That two extra ADC with the non-PDIP ones come in handy.

[Psi]

It’s 328 and 328P. Letters after the dash indicate the ordering code. For both of them, not only 328. The ordering code is internal to Atmel/Microchip and its meaning is not documented. While some have been correlated with packaging type, binning or delivery options, other remain a mystery.

You are mentioning an U code, which is not listed in datasheets for ATmega<X>8 series, but that’s not the first time such components surface. However, be sure to check if that’s not AU, MU or PU: those are QFP, QFN and PDIP packages.

Be VERY careful with the letters on the end of AVR mcus, sometimes it matters, other times it doesn't. But it ALWAYS means you need to check.

eg, ATMega328  vs ATMega328P vs ATMega328PB   
(PB does not mean lead/leadfree, it's got different physical hardware support, QTouch, Peripheral Touch Controller etc)

Also
ATTiny2313  vs ATtiny2313A vs ATtiny2313V
The A version is a newer iteration and has PCINT on all pins but the non-A only has PCINT on some pins.
The V version is a non-A type that can run on lower voltages.
So if you designed your hardware for one you could run into real problems if you got the other on the board.

But it gets worse, When they came out with the newer 'A' type 2313A they also decided to come out with a 4KB flash version.
Since there was no prior 4313 part they called the new one 4313 and not 4313A like you would expect.
So you have ATtiny2313 and ATtiny4313 and the 4313 is the newer version with extra PCINT but the 2313 is the old version without it.   

[golden_labels]

Note that what Psi refers to are letters that are a part of the device number. They are well documented in the datasheets, even if the datasheets may be not readily available for older parts and noticing the differences may require a lot of careful reading.

The meaning behind the ordering codes is unknown and only partial guesses are available based on what can be found in the relevant datasheet sections (at the end).

[Nusa]

https://forum.arduino.cc/t/atmega328p-u-incompatible/540160/ discussion includes this gem from Microchip:

As part of Part marking change due to the migration from Atmel to Microchip, the package identifier has been removed from the device marking as this can be observed visually for different packages. This will be updated in the upcoming revisions of the device datasheet. As per this new marking the ATMEGA328P U are valid devices without any process change. Please provide more details on the application and nature of failure so that we can check this further.

[tooki]

You are mentioning an U code, which is not listed in datasheets for ATmega<X>8 series, but that’s not the first time such components surface. However, be sure to check if that’s not AU, MU or PU: those are QFP, QFN and PDIP packages.

Ref the image I had posted...
Also, I am not sure that the body is not made of plastic. It is DIP though.

The only alternative to plastic DIP is ceramic DIP (CDIP), which you definitely don’t have. They look different (kinda purple-gray, in layers), they feel different (heavier, colder), and they’re a LOT more expensive. (Very few ceramic DIPs are made any more, mostly for military grade parts.)

(I suppose some old optoelectronics parts were DIPs in colored epoxy, but that still falls under “plastic” DIP.)

[samarth]

https://forum.arduino.cc/t/atmega328p-u-incompatible/540160/ discussion includes this gem from Microchip:

As part of Part marking change due to the migration from Atmel to Microchip, the package identifier has been removed from the device marking as this can be observed visually for different packages. This will be updated in the upcoming revisions of the device datasheet. As per this new marking the ATMEGA328P U are valid devices without any process change. Please provide more details on the application and nature of failure so that we can check this further.

So that means that what I have is the "P" version of the atmega328?
Or is my reading comprehension out of whack due to lack of coffee
SR

[wraper]

No, You would have a P letter on it if it was 328P. What you have is Atmega328-PU. 328P in dip package would have part number Atmega328P-PU.

[wraper]

Older marking of 328P looked like this:


Newer look like this with letter indicating the package type eliminated:

[samarth]

Understood, thanks!

[westfw]

The ATmega328P is the "Picopower" version.  It has an option to turn off the Brown-out-detection via the MCU Control Register (BODS and BODSE bits); it MIGHT have lower power consumption in various sleep modes, too.
In 10+ years of people getting the wrong chip for their Arduinos, that's been the only actual difference that anyone has been able to detect.  :-)
The 328 and 328P also have different chip signatures, which you'll need to account for when programming them.  For Arduino, you can load up a bootloader that identifies the chip as a 328P even if it's a 328, and it will save you a lot of trouble.  But you have to specify that it's a 328 during the burning of the bootloader.

[rpiloverbd]

From your photo I can see that your chip is ATmega328. The letter after the dash(-) indicates the package type. Here are some answers regarding this issue.

https://arduino.stackexchange.com/questions/66694/atmega328p-u-vs-atmega328-pu