Arduino Pro Mini - How many varieties ?

Its really confusing as the on - line stores seem to have so many different types. I have a few which has A6 and A7 pins … then there is this one on Ebay which has a slightly different layout :


Question is whether there is any standard Pro Mini design as we have the UNO R3 ? The reason i am asking is i am planning to make a PCB to mount this and if i use a non-standard one then i am stuck if that vendor packs and goes home !

Any guidelines ??

Located one more on EBay itself and this one claims " Official Version " !

Just want to know if its truly the official version ??



Buy the “official” one from Arduino, not eBay.

In my experience they all work the same.

There are indeed many varieties, but up to A3 they are all the same. But yeah, if you want to use I2C things can get a little bit harder.

And to make it even a little bit harder, luckily not for the PCB, there is also a stupid version which has the FTDI pins in reverse order...

There are at least three different versions that I've seen.

The official version has A4~7 in these weird half-pitch locations for reasons I've never understood, making it very hard to use with generic prototyping board - (I sell project boards made for the pro mini, which break those out to more convenient locations Browse products by Azduino by Spence Konde on Tindie).

Then there are those black ones, with A4~7 in the middle along the edge opposite the FTDI connector. IMO this is the worst layout, because it's both incompatible with generic breadboard and doesn't match the official layout.

Then there are the ones with a double-row header along the end opposite the FTDI pins - these extra 10 pins include an ICSP header, and the 4 analog pins. This is my preferred layout, as it gives you a convenient ICSP header, and keeps the analog pins on a 0.1" grid. IMO, this should have been the official layout (I feel that an ICSP header should be included on any AVR based development board)

1 Like

If you’re making a PCB, why not just put the components on the board? Then you’re not depenendent on some outside group and 3-4 week shipping times and vagaries of supply, etc.
'328P, crystal/caps or resonator, 10K resistor, 4 0.1uF caps, maybe a voltage regulator depending on your power supply.

I have 5 versions.
All work.
There are 5v16Mhz and 3.3v8Mhz versions.


A6 & A7 are analog input only, if you’re not using them than a DIP part is all you need.

I like to use a Pro Mini as well. They are dirt cheap (cheaper then separate components) and you get extra PCB room for free. Also, if you want to share it with people who don't like SMD you can make the rest TH.

But I must say, I like the version DrAzzy hates the most :stuck_out_tongue: Yes, those pins will not fit a breadboard but so will the 10-pin version. And I just find the 10 pins a bit much and find a single row easier. And if you want to have access to those pins on a breadboard, just solder headers on top. This can also be an angled header which I think is also easier with the single row version. :slight_smile:

I agree with DrAzzy. All pins on the standard grid and ICSP header in that small of a form is great. I have a bunch of different Pro Minis but I’ve decided to only buy that model now. The reset button does interfere with soldering on the ICSP header because it’s a little too close to those pins but you only need to cut some plastic off the corner of the header with a knife or use a pogo adapter if you don’t program them via ICSP very often.

Ok looks like I have not been the only one who faced this variants ! But by and large the Blue Official version is the one I will go with ... thanks for that confirmation.

@DrAzzy : I can see your point on the A4-A7 sitting inconveniently for a bread board...but when I make a PCB I guess this is not an issue. Otherwise the PINs match the Official version. Somehow this Black one looks very nicely done with the big crystal and all !!

@CrossRoad : Yes I am also a big fan of the bare bone version and hardly ever use the regular modules like UNO. But for projects needing more than few PCBs its nice to go with a designed PCB and not a GP. And in my part of this world...getting small volume custom PCBs ( 5 to 10 nos ) of the SMT type is impossible. Its not about money - even if you are willing to pay nobody is keen to do it. So in those cases the ProMini is a God send

It's almost hard to fine two ProMinis that are the same these days. There are TONS of slightly different variations, with really annoying differences. Some have A4 and A5 0.050" offset from the edge pins, while others have them ALIGNED with the edge pins. Some have the programming header reversed. Some have A6 & A7 swapped. Some have the VCC/GND pins at the A6/A7 end of the board swapped. Some have TWO rows of pins at the A6/A7 end of the board. The dimensions vary all over the map, with some boards LOOKING the same, but one will be longer or shorter than another, with the programming header, A6/A7/VCC/GND pins further from the long rows of pins. It's infuriating. Even worse, when you buy them online, there is NO guarantee what you actually receive will match the photos in the ad. At least with E-Bay, if this happens, you can dispute the sale, and it is the SELLERS responsibility to arrange pre-paid return shipping. Most will simply tell you to keep them. I've had well over $1000 of purchases refunded, and got to keep the product, because of this.

Ray L.

Ray, how 'bout a Dummies book on that "refund and keep" thing. :grin:

eBay uses seller rating to influence where listings appear in the default "Best Match" search results. It can also affect seller fees. So one disgruntled customer can cost a seller much more than the price of the item. For this reason I find excellent customer service on eBay, though it can be frustrating when you're a seller dealing with an unreasonable customer. I've considered using this as a way to fight counterfeits: Order an item you know is a counterfeit (e.g. a $5 Uno that has the "made in Italy" silkscreen of an official Uno). If it shows up with that silkscreen then you report the item as a counterfeit. If it shows up with a different silkscreen then report the product is not as described in the listing. You help Arduino and get a free clone as a reward!