John Syn <john3...@gmail.com> wrote: > > On 9/7/14, 2:07 AM, "c...@isbd.net" <c...@isbd.net> wrote: > > >John Syn <john3...@gmail.com> wrote: > >> > > >> >I'd love to find a document or tutorial that describes how this all > >> >hangs together but there doesn't seem to be anything other than the > >> >(huge) processor documentation which is vey much reference material > >> >and (as I referred to above) various blogs etc. showing how to do one > >> >particular thing but without any attempt to explain it. > >> The pinmux section uses the register offset and in the attached > >> spreadsheet, that offset is related to the P8/P9 connector pins. > >> > >> The right column defines how the pins are setup in the V3.15-bone5 > >>device > >> tree. > >> > >Thanks, but attachments don't work when using news group access to > >gmane (or at least I don't think they do, I couldn't see anything). > > > >Could you possibly point me at a URL for the spreadsheet or mail it to > >me directly (E-Mail in header works). > To explain how the spreadsheet works: > > If you look at the AM335x TRM, start with the CONTROL_MODULE Registers in > Section 9.3.1. The first I/O pin is conf_gpmc_ad0 which is at offset 800h, > but the pinmux in the device tree defines this as address 0h so you always > have to subtract 800h from the offset from this table. On the right > column, you will see a reference to 9.3.1.50 which defines the mode, pull > up, pull down, etc. Now you have to use either the schematic or the BBB > SRM to map the processor pin (conf_gpmc_ad0) to a board connector pin > (P8_25). > I think the fundamental thing that I hadn't grasped until now is that each individual IO pin can be multiplexed independently. From the way that the BBB manual shows the pinouts it seemed (to my old fashioned hardware knowledge) that one had to select one of the eight MUX settings and that would define what all the pins do.
Now that I realise one can MUX each pin things begin to make a bit more sense (at least I hope they do and that I have this right!). -- Chris Green ยท -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
