Larry Howell <[email protected]> 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. > > > Hi Chris, > > The BBB SRM gives information about the BBB, but doen't go into details > about the AM3358 processor. I'd suggest reading about pinmux in the > AM335x Sitara Processors Technical Reference Manual, which can be found > on the TI website. Basically, there are far more I/O features than > pins on the processor. Eight times more signals than pins to be > exact. The modes allow selection of which one of the eight for a pin > you choose to use. The TRM will provide the details on the mode that > enables a particular function for a specific pin. > > Searching for "pinmux" will find many documents and tools. > Hmm, yes, I know the AM335x Sitara Processors Technical Reference Manual is the ultimate reference but it is (as I said) an absolutely huge document and is hardly the place to start if trying to gain an understanding of this stuff.
I do understand the concept of multiplexing, it's hardly a new idea (I cut my microprocessor teeth on 8080s, Z80s, 6502s and RCA 1802s) and the BBB SRM points one in the direction of how it's used on the BBB. However very, very few of the documents I've found give any clue at all on how the ready made IO libraries (such as the Adafruit ones) or the device tree itself control (or map onto) the MUX configurations. >From my past I'd sort of expect to be able to simply switch between MUX modes by issuing a write to a register somewhere, so the Mux modes shown in the BBB SRM would then be directly selectable but this doesn't seem to be the way the BBB works. -- Chris Green · -- 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
