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RDK
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Pins vs GPIO pins??

Wed Jan 07, 2015 6:26 pm

Folks...I'm confused, not an unusual state for me :-)

I'm reading the Raspberry Pi User guide and have arrived to the project (Chapter 15) with the LED's, etc. The author introduces the GPIO connector (40 pins for my B+) and then proceeds to tell me how to set up a simple LED blinker project, but with lots of warnings about 3.3V vs 5 V and improper voltages to the LED's.

My confusion starts when he tells me to connect "pin 11 of the Raspberry Pi's GPIO port to ...". When looking at the associated Pi GPIO drawing, I see 40 pins, numbered from 1-40. BUT, in the descriptions for each pin, some say "GPIO Pin 6" which is associated with pin 31 in the drawing.

So, which is pin 11? The one as 11 counting from left to right or #23 which is labeled GPIO Pin 11/SPI/SCLK?

Thanks.....RDK

ps...yes I'm still a beginner....

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DougieLawson
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Re: Pins vs GPIO pins??

Wed Jan 07, 2015 6:34 pm

It's OK you are not alone the pin mis-numbering is designed to make it really hard for every one.

There are 26 or 40 physical pins numbered from 1 to 40. Pin 1 is nearest to the dsi display connector. Pin 25 or pin 39 is closest to the USB connector.

Odd pins to the left and even pins to the right.

That is BOARD numbering.

Then there's numbering them by function or GPIO connection to the SoC. That's "Broadcom" or BCM numbering.

I think http://pi.gadgetoid.com/pinout makes it easiest to work out where you are and what pins you need to connect.
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joan
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Re: Pins vs GPIO pins??

Wed Jan 07, 2015 6:46 pm

The pins are the pieces of wire which stick up. Some of the pins are internally connected to gpios (general purpose input outputs) which may be controlled in software (to set that pin to 0 or 3.3V).

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RDK
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Re: Pins vs GPIO pins??

Wed Jan 07, 2015 7:43 pm

Dougie...I see the diagram and understand the correspondence, BUT I still don't know how to interpret the instructions in the LED project in Chapter 15 of the Raspberry Pi User guide. Which is the correct pin 11? Physical layout number and GPIO designation?...RDK

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DougieLawson
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Re: Pins vs GPIO pins??

Wed Jan 07, 2015 7:44 pm

It means physical pin #11 which is GPIO 17.
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RDK
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Re: Pins vs GPIO pins??

Wed Jan 07, 2015 8:12 pm

OK, thanks. I will approach that project with a bit more confidence.....RDK

ps...I'll check back when I actually have the components and the board working. Or, possible, smoke and fire....

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DougieLawson
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Re: Pins vs GPIO pins??

Wed Jan 07, 2015 9:06 pm

If you think the book could be improved see here: http://www.raspberrypi.org/forums/viewt ... 95#p186995
If you want to download the code to save typing things in see here: http://eu.wiley.com/WileyCDA/WileyTitle ... 6446X.html
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