Howdy -
The pinout for the Pro Micro shows 3 pins labeled "GND":
Pins 3 and 4 (counting down from J1), and pin 23 (right before the "RAW" pin on the other side) are all labelled "GND" - but I think the are not the same.
If anyone is willing to agree with me and state that "they are not the same" - please explain and include a reference if you have it. I've looked here (and on the web a little), but c'mon... It should be well documented on the official site, right?
Thank in advance.
I think the onus is on you to back up your claim, not expect others to do so.
If it’s a Pro Micro, it’s not a true Arduino product, ergo no schematic from them, and you’ve posted in the wrong category.
Schematics from Oshwlab.com found online do not differentiate, using identical symbols for all those GND pins; that would indicate the CAD program used linked them all.
Evidence?
Just the basic "probes on the chip" type... They're not the same electrically - which I believe means they were intended to serve different functions.
To be clear, are you saying you used an ohmmeter, and measured more than, say,1 ohm of resistance between the GND pins? If so, the first thing I would suspect is a poor solder joint on one of the pins. Are they pins, and are they soldered in, or were you measuring the pin hole to pin hole, before soldering in the pins?
A photo of the board, and solder connections if any, are required. Clear, well focused, please.
Pins are all soldered in. I checked several (3) of my protoboard units, and they all show the same characteristics - including one that I just removed from the packaging about an hour ago. I'm certified "Hi-Rel" soldering (and wire-wrap, too !!!) so, my joints are good. I appreciate your help - let's see if anybody out there knows the answer... Thanks again for the inputs.
Sorry, but…
Oh! I'm the sorry one. Yes, more than 1MegOhm. I will tell you that 2 of the three pins read a dead short to the USB connector's outer "shell" but not to the third pin - and one more thing: I only paid about 5 USD for each of these on Amazon - so probably not original Arduino equipment. I also have one other unit (I think it's the first one I ever bought, about a year ago) which does not show the same characteristics... so a changed attribute possibly? Really - there's no rush here. My prototypes are working, and I have work to do yet - so please don't expend too many clock cycles on this - I just wanted to put it to rest. I've seen some posts that insisting that there's no difference - I only seek the truth. Thanks again.
We do believe you. Now, trace the unknown ground pin back to some chip and tell us what that is.
GND is GND is GND, there’s 3 of them. Use any or all of them you want. Just like Pro Mini, Pro Micro is a Sparkfun product. Get the official documentation from Sparkfun.com, including the schematics, Eagle files, and other information. Pro Mini got an “endorsement” or blessing from Arduino to call it an “Arduino” but Pro Micro never got that. Arduino has the “Micro” and there is no such thing as “Arduino Pro Micro” although people sometimes call them an Arduino. In any case, the documentation comes from Sparkfun.
See the schematic: https://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/Pro_Micro_v13b.pdf
So I can't agree with you that they are not the same.
Which official site?
Then quite simply there is a fault with your board. All ground pins are the same.
By the way most of the time Amazon sell crap at inflated prices, don’t believe the hype.
Thanks, Mike -
I've now realized that I've got the knock-off version from Amazon. (The brand name is "HawkMaker"). They might be totally different under the hood, but they are working for me - and why would anyone pay 22 us dollars for 1 SparkFun version when I can get 5 for 29 bucks? And it's not a board fault - all 5 of the ones I just bought are the same. They shouldn't be allowed to sell rip-offs! I'm just wondering why they all say "GND", but aren't connected electrically... Thanks again for the input.
Howdy - thanks for the input. I've just realized I don't have the SparkFun product. It's a knock-off - but it's working for me - and I did find that doc a while ago - but it doesn't really help. But my meter doesn't lie !!! Usually. Two of the pins aren't connected to the third. That's gotta mean something. Just trying to figure it out. Thanks again.
I don't have the actual SparkFun product. Amazon knock-off ! Still, if it's different than the original, there has to be a reason one pin isn't connected to the other two, right ? Just trying to figure it out. Thanks for the input - much appreciated.
Howdy - I did not mention before that these are "knock-offs" of the actual SparkFun product. apparently, the manufacturer has no media presence that I can find, and they probably don't speak my language. I just want to figure out how this thing works! Thanks for the input.
Well to avoid the “problems” like you are having in thinking there is something special about one of the ground pins.
In life you normally get what you pay for when it comes to low quality clones.
Probably either a bad circuit board design, or a production problem. Bad plating on a through hole that was meant to connect to the ground plane could cause it.
If you can post clear close-up pictures of your soldering job on the pins and the board markings perhaps it will reveal the problem.
With five boards exhibiting the same issue, I’d say it’s either a design or production fault, and you should simply tie all 3 together anyway, and move on. As long as the device works in that arrangement. Odds are good they floated the pin inadvertently and it’s connected to nothing, but it could also be that the ground of one or two components are tied to it and nothing else, so unless you connect them externally something isn’t functioning.
HTH
