Hey guys. Can anyone shed any light on the numbering system for the pins?

Electronics
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1

Hey guys. Can anyone shed any light on the numbering system for the pins? I get the P9_21 stuff, pin modes, and most of the other stuff. I even know from diagrams that is internally pin 85, but I am having trouble finding where that pin number relates back to the rest of it.
For example:
If I go to /sys/kernel/debug/pinctrl/44e10800.pinmux, and type “cat pins” I get a whole list of pins along with their settings. That all makes sense, but where does the pin number come from? If I don’t know P9_21 is pin 85, how would I look that up and associate it with useful info?

I can look up the pin number thanks to the work of folks like @Derek_Molloy , but I would still like to know how to find this number without relying on charts. It would be much easier to just be able to enter something at the command line.

2

Perhaps I could add some more info to this:
root@beaglebone:~# node -p -e “require(‘bonescript’).getPinMode(‘P9_21’);”
{ pin: ‘P9_21’,
name: ‘UART2_TXD’,
options:
[ ‘spi0_d0’,
‘uart2_txd’,
‘i2c2_scl’,
‘NA’,
‘NA’,
‘NA’,
‘NA’,
‘gpio0_3’ ],
mux: 7,
slew: ‘fast’,
rx: ‘enabled’,
pullup: ‘pullup’ }

3

the schematics are in pdf on
http://circuitco.com/support/index.php?title=BeagleBoneBlack#Hardware_Files

You can follow the expansion port all the way back to the micro.

4

@Jason_Kridner That looks really interesting, and does lay out the data quite nicely. I’ll have to look more into bonescript, and see if there is a way to get the pin address/number.

@Andrew_Bradford Indeed they are not. It’s looking more and more like I have to rely on them. BTW, are you sure the names are right in your tables? They seem different from the ones in the SRM (p.82).

@Jimmy_Edwards That’s where I got the SRM. Having a look at it, the diagrams are a great resource, but I can’t find where the pin number is located. I can trace UART2_TXD (pin 85 in the software) from start to end, and I don’t see the number listed. I did find the proc ID though, which is interesting.

I guess where I’m really getting confused is that to use P9_11 and P9_13 (UART4) in a device tree overlay, I use the address offsets of 0x070 and 0x072. This offset number is quite easy to find if I know the pin numbers. Just subtract 800 from the last three numbers of the pin address. I can’t find how to locate this address in the documentation. In the SRM on table 17 there is an entirely different offset given.

It’s not vitally important, as there are resources that list them. It’s just going to bug me until I figure out where they come from. :slight_smile: