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Rude eBay Vendor

I was looking through some rPi stuff on the web and found a ruler that includes holes for the rPi expansion connector and info on how to program the IO along with.... well, ruler markings. Nice gadget but they want about $5 for it, plus shipping.

So I looked on eBay and found several similar rulers, but without the ruler markings. One of them had two different pictures with different markings on the labels next to the pin numbers. I wrote them asking which one was right and what the labels mean, "Wiring Pi" on one and "BCM GPIO" on the other. Not being intimate with the Pi IO, I am guessing these numbers are the IO port bit numbers. But why the two different labels in the same listing?

So I wrote and asked, pointing out that these must be two different boards as the pin numbers are the same on each board. Unless... I see the labeled numbers are not the same between the two. Would it make sense that this is one board with different info on the two sides for different versions? I seem to recall another vendor doing that and labeling the two sides with the version numbers. The two sets of numbers on this board do not match that.

It looks like the BCM GPIO numbers match the numbers of the GPIO bits for rev 2 boards on other units like this. But I can't tell what the Wiring Pi numbers mean. Here are a few pins on the connector.

P N W B i a i C n m r M e i G n P g I P O i

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1 3.3V 3 SDA 8 2 5 SCL 9 3 7 G7 7 4

Obviously I would learn a bit more about this when I actually used it for connecting I/O to the rPi. I have only connected through USB so far.

The "rude" part comes in that when I asked the vendor about the two sets of numbers, the reply was, "You probably don't need this if you have no idea what it is." No further info.

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Rick C
Reply to
rickman
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Well, my response to that is "You probably don't need to buy anything from this vendor if they have no idea how (or inclination) to properly answer your questions."

I think the *best* answer to your question, though would come straight from the source; that is the author of the wiringPi library:

formatting link

I hope this helps.

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Sylvain Robitaille                               syl@encs.concordia.ca 
  
Systems analyst / AITS                            Concordia University 
Faculty of Engineering and Computer Science   Montreal, Quebec, Canada 
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Reply to
Sylvain Robitaille

Yeah, I guess it helps. I never would have imagined that someone would add a third numbering scheme to the existing ones.

I do want one of these boards and this one is the cheapest. I expect I will order the board. But there is more than one way to skin a cat.

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Rick C
Reply to
rickman

Some (well me) say that I added the first numbering scheme and the others followed.

formatting link

Gordon

Reply to
Gordon Henderson

Must update that... One day..

The easiest way is to run

gpio readall

in a terminal. That way you get a picture of the GPIO connector on the Pi you're running it on with all the numbers you could ever want!

Gordon

Reply to
Gordon Henderson

I have to say, I am a bit more confused rather than less. On your web page you talk about three numbering schemes...

I get that the wiringPi is an arbitrary numbering scheme that abstracts the hardware and provides a means of controlling the I/O pins on the connector without changes between versions of the rPi. I don't understand what the other two are. I don't know if "native hardware pin numbering" means the pins on the CPU chip or the pins on the connector. Then "physical pin numbers" leaves me completely confused. What part of hardware is not "physical"?

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Rick C
Reply to
rickman

Unless I am very much mistaken I would read it like this

Native Hardware pin numbers will be the pin numbers for the SOC as per the broadcomm documentation.

Physical pin numbers will be pin numbers on the 40 pin header.

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... the flaw that makes perfection perfect.
Reply to
alister

I actually have wPi installed on my model 1B that runs the RASPBX phone system here, but I don't use it to operate the 8 relays that can be "dallied" as I didn't find it too confusing to count 1-8 as 17,18,27,22,23,24,25,4, the sequence is now hardwired into my brain :-) I did have to scratch my head to figure out why the 8th relay refused to work until I realized that 04 was wrong in the shell script, it was just 4. That's why I now write gpio in lower case!

One thing your site did teach me was that gpio2 and gpio3 don't need pullups, so these were my preferred inputs for the two door entry call buttons.

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Graham. 

%Profound_observation%
Reply to
Graham.

If you ever have the misfortune to use a Pi v1, then you'll need to remember 17,18, 21, 22, ...

and on a v1 those are bcm_gpio 0 and 1 ...

Cheers,

Gordon

Reply to
Gordon Henderson

Why would anyone care about the pin numbers on the SOC? Is it because the documentation of the SOC is in terms of those pin numbers? I would expect the SOC docs to mostly refer to the internal registers and only relate that to chip pin numbers in a table somewhere. In other words, I can't see much reason to worry with the SOC pin numbers, rather I would focus on the view from the software (register addresses and bits) and the view from the hardware (board connector pin numbers). SOC pin numbers are only useful if you are trying to trace out the connections using the board level documentation.

I recall reading from the Broadcom manual once and the docs are in terms of the internal registers.

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Rick C
Reply to
rickman

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